CA1125755A - Synthesis of 2-keto-1,4-diazacycloalkanes - Google Patents
Synthesis of 2-keto-1,4-diazacycloalkanesInfo
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Abstract
ABSTRACT OF THE DISCLOSURE
A polysubstituted 2-keto-1,4-diazacycloalkane trans-isomer is produced by reacting a trans-1,2-diamino-cycloalkane in water with a hydroxy fatty acid nitrile.
A polysubstituted 2-keto-1,4-diazacycloalkane trans-isomer is produced by reacting a trans-1,2-diamino-cycloalkane in water with a hydroxy fatty acid nitrile.
Description
11'~5'75''j This invention relates to the synthesis of 2-keto-1,4-diazacycloalkanes A
This application is a divisional application of Canadian Patent Application S.N. 310,371, filed August 30, 1978.
Organic materials, whether natural or synthetic, are conventionally protected against degradation bv ultraviolet ( W ) light by incorporating a UV light stabilizer in the material. Many classes of compounds are known to be useful UV light stabilizers, some being more effective than others. Particularly effective com-pounds, which provide compositions resistant to degradation by UV light, include the decahydroquinolines disclosed in UOS. Patents 4,069,195 and 3,073,770, the 1,5-diazacycloalkanes and 2-keto-1,5-diazacycloalkanes disclosed in U.S. Patent 4,027,228 and, the 2-keto-1,4-diazacycloalkanes disclosed in U.S. Patent 4,190,571.
Other cycloalkanes useful as W light stabilizers are disclosed in German Offenlegungsschrift 2,315,042, Japanese Patent Numbers 7,453,571 and 7,453,572, and in U.S. Patent Numbers 3,919,234, 3,920,659 and 3,928,330 which teach substituted piperazinediones.
The substituted piperazinediones are difficult to prepare, particularly with dialkyl substituents on each of two N -adjacent symmetrical carbon atoms (here-after "symmetrical c atoms"). Once prepared, however, they may be reduced to the tetraalkyl substituted piper-azine as disclosed in German Offenlegungsschrift
This application is a divisional application of Canadian Patent Application S.N. 310,371, filed August 30, 1978.
Organic materials, whether natural or synthetic, are conventionally protected against degradation bv ultraviolet ( W ) light by incorporating a UV light stabilizer in the material. Many classes of compounds are known to be useful UV light stabilizers, some being more effective than others. Particularly effective com-pounds, which provide compositions resistant to degradation by UV light, include the decahydroquinolines disclosed in UOS. Patents 4,069,195 and 3,073,770, the 1,5-diazacycloalkanes and 2-keto-1,5-diazacycloalkanes disclosed in U.S. Patent 4,027,228 and, the 2-keto-1,4-diazacycloalkanes disclosed in U.S. Patent 4,190,571.
Other cycloalkanes useful as W light stabilizers are disclosed in German Offenlegungsschrift 2,315,042, Japanese Patent Numbers 7,453,571 and 7,453,572, and in U.S. Patent Numbers 3,919,234, 3,920,659 and 3,928,330 which teach substituted piperazinediones.
The substituted piperazinediones are difficult to prepare, particularly with dialkyl substituents on each of two N -adjacent symmetrical carbon atoms (here-after "symmetrical c atoms"). Once prepared, however, they may be reduced to the tetraalkyl substituted piper-azine as disclosed in German Offenlegungsschrift
2,315,042. ~here is no suggestion as to how a mono-keto structure, that is a 2-keto-1,4 diazacycloalkane structure, may be prepared with a total of two or more (hence "polysubstituted") substituents on symmetrical C atoms.
It is known that 4,4,6,6-tetramethyl-1,5-diazacycloheptan-2-one may be prepared by a Schmidt's rearrangement of a six-membered ring with sodium azide (see German Patent Number 2,428,877) but there is no known manner of similarl~ arriving at a six membered 1,4-diaza ring with an N -adjacent carbonyl, -- 1 -- ~
1125'755 - la -It is known 1,4-diaza(3,3,5,5)-dipentamethylene-2-one may be prepared, starting with cyclohexanone by cyclization of bis(l-cyanocyclohexyl)amine, reducing with lithium aluminum hydride to form 1,4-diaza(2,2,5,5)-dipentamethylene-2-imino, treating with acetic anhydride and heating with hydrochloric acid. This is set out in greater detail in an article by Helmut Egg in Monatshefto fur Chemie 106, 1167-1173 (1975). However, starting with acetone instead of cyclohexanone, the reactions do not proceed in an analogous manner to give 3,3,5,5-tetramethyl-piperazin~2-one. This Egg reference teaches substituted piperazines wherein each symmetrical N4-adjacent carbon is part of a six membered ring and the cyclic substituent on each N4-adjacent carbon is always the 11;~575S
same. A single cyclic substituent on the N4-adjacent C atom oî the fixed two-carbon bridge cannot be prepared by following the techniques of Egg.
Cis-3,3-dimethyl-decahydroquinoxalin-2-one has been prepared by cis-1,2-diaminocyclohexane, and it is disclosed that the cis-compounds are valuable 5 intermediates for the production of pharmaceuticals, textile auxili~ry products and synthetic materials. This reference states that the trans-1,2-diaminocyclohexaneis converted, with excess chloracetic acid, or with salts thereof, into 1,2-diaminocyclohexane-N,N'-tetraacetic acid, which is quite unlike the behavior of the cis starting material. The cis-2-keto-1,4-diazacycloalkane is prep~red by reacting 10 an aqueous solution of cis-1,2-diaminocyclohexane with acetone cyanohydrin, and heating the reaction solution to dryness. The reference does not teach formationof a trans-5,6-polyalkylene-2-keto-diazacycloalkane, and there is no suggestion as to how it could be made. In fact, it is to be understood that the trans-2-keto-1,4-diazacycloalkane cannot be made, since Bindler states that cis-1,2-diaminocyclo-15 hexane behaves differently from trans-1,2-diaminocyclohexane; the positioning of the two primary amine moieties imparts distinctly different properties to the isomers. This dfference, and particularly the essential difference in cyclization behavior of the primary amine moieties, is used to advantage in the separation of the isomers. The cis isomer cyclizes and complexes with Ni and Cu; the trans 20 isomer does not. Nevertheless we have found that trans-2-keto-1,4-diazacyclohex-ane can now be formed in a manner analogous to that in which the cis-2-keto-1,4-diazacyclohexane is formed.
Following the teachings of Bindler, ethylene diamine may be substituted for cyclohexanediamine, and 3,3-dimethyl-2-keto-piperazine is obtained. However,25 when a substituted ethylene diamine is used, the substituents appear on the No. 6 carbon of the diaza ring. For example with 1,2-propane diamine, 3,3,6-trimethyl-2-keto-piperazine is formed; and with 2-methyl-1,2-propane diamine the compound obtained is 3,3,6,6--tetramethyl-2-keto-piperazine. No. 6-substituted and 3-substituted carbons are not symmetrical carbon atoms about the same N-adjacent 30 atom in the diaza ring (hereinafter referred to as "symmetrical N-adjacent C
atoms"). These compounds are quite unlike the novel compounds claimed.
Moreover, 3,3,6,6-tetraalkyl substituted diazacycloalkan-2-ones, in which the substituents are not on symmetrical N-adjacent C atoms, are selatively ineffective UV stabilizers, confirming my experience that the more substituents on symmetri-35 cai N-adjacent C atoms, the better the stabilization effect.
It is known that 2,2,4-trimethyl-tetrahydroquinoline can be hydrogenat-ed to form a mixture of cis and trans 2,2,4-trimethyldecahydroquinoline, and, ingeneral, the trans isomer is the major constituent. However, 2,2-dimethyl-tetrahydroquinoxaline is not hydrogenated in an analogous manner.
_ 3 _ ~1~57SS
It is to the problem of synthesizing polysub-stituted 2-keto-1,4-diazacycloalkanes, efficiently and economically, so that they can be manufactured for com-mercial use, that this invention is directed.
It has been discovered that polysubstituted 2-keto-1,4-diazacycloalkanes may be prepared from readily available starting materials, in simple, conventional apparatus, without the high risks attendant upon using hydrogen cyanide. This may be done by any of several novel syntheses.
A. A novel synthesis has been discovered wherein cis-3,3-dialkyl-3,4-dihydroquinoxalin-2-one is hydro-genated in the presence of a suitable hydrogenation catalyst, at elevated temperature and pressure, to yield a cis-3,3-di-alkyl-decahydroquinoxalin-2-one.
B. A novel synthesis has been discovered wherein trans-1,2-diaminocyclohexane is reacted with acetone cyano-hydrin in the presence of water to yield trans-3,3-dimethyl-decahydroquinoxalin-2-one.
C. A novel synthesis has been discovered (herein-after referred to as "the cyanohydrin synthesis"), wherein a cyclic or acyclic 1,2-diamine is reacted with cyclic or acyclic cyanohydrins in the presence of a suitable organic solvent in the presence of aqueous ~aOH at ambient temperature and pressure, in the presence of an "onium salt"
(defined hereinafter) catalyst in conjunction with a halo-form, to yield a polysubstituted 2-keto-1,4-diazacycloalkane.
D. A novel synthesis has been discovered (herein-after referred to as "the ketoform synthesis") wherein a preselected 1,2-diamine is reacted with a saturated acyclic or cyclic monoketone, and, a haloform, in the presence of (i) an onium salt catalyst (ii) an organic solvent, and (iii) aqueous alkali.
The present invention is more particularly concerned with synthesis B.
, ,, `` 1125~55 The basic structure of the compounds prepared by the syntheses described herein, is a polysubstituted (hereafter also referred to as "substituted" for brevity) 2-keto-1,4-diazacycloalkane having (a) a fixed two-carbon bridge between the two N atoms (the Nl and N4 atoms) of the diaza ring, the remaining portion of the ring having a variable length bridge of two or more carbon atoms, (b) an Nl-adjacent carbonyl in the fixed two-carbon bridge, and (c) at least the N - adjacent carbon of the fixed two-carbon bridge has two substituents (hence "polysubstituted"), which may be cyclizable, that is, form a cyclic substituent. These compounds which may be monocyclic, or with cyclizable substituents, may be bicyclic or tricyclic, are particularly useful as UV light stabilizers in substantially 1125~55 colo~less organic materials. The compounds may also form dimers and bis-compounds. The diaza ring of the basic structure may have from 6 to 9 ring members, more preferably from 6 to 8 ring members, and most preferably from 6 to 7 ring members.
These substituted 2-keto-1,4-diazacycloalkanes characteristically have two substituents, which may be cyclizable, on the N4-adjacent C atom of the fixed two-carbon bridge. They are particularly useful as UV light stabilizers in compositions subjected to UV light degradation. As stabilizers they are used in the range from about 0.01 to about 5 parts by weight, and preferably from about 0.1 to 10 about 1.0 part per one hundred parts (phr) of organic material subject to UV light.
These materials may be low or high molecular weight materials, and particularly include homopolymers, copolymers and mixtures thereof. Examples of materials that can be stabilized against degradtion due to UV light are oils; monomers, particularly , ~ -olefinically unsaturated monomers such as acrylates, dines, vinyl 15 nitriles, and the like; and other relatively lower molecular weight materials than synthetic resinous polymers, such as alcohols, aldehydes, and the like. Exflmples of known mater;als which can be stabili~ed with polysubstituted 2-keto-1,4~iazacy-cloalkanes are natural rubber, synthetic rubbers such as cis-polystyrene, polyacryl-onitrile, polymethacrylates, polycarbonates, varnish, phenol-formaldehyde resins, 20 polyepoxides, polyesters, and polyolefin homo and copolymers such as polyethylene, polypropylene, ethylene-propylene polymers, ethylene-propylenediene polymers, ethyl-vinyl acetate polymers, and the like. The substituted 2-keto-1,4~iazacyclo-alkanes can also be used to stabilize mixtures and blends of polymeric materialssuch as ABS resin blends, PVC and polymethacrylate blends, and blends of 25 polyolefin homopolymers and copolymers such as blends of polypropylene in epdm polymers.
The 2-keto-1,4-diazacycloalkanes prepared by the syntheses of this invention have the structural formula: R1 2)m ~ R -- -- (I) 30 wherein, m represents an integer in ~he range from 2 to 7, being the number of methylene groups fol ming a bridge of variable length, and some of which groups (a) together with the carbons to which they are bound, may form a cyclopentyl, cyclohexyl or cycloheptyl endo ring, or (b) be substituted; when m is 2 then (I)represents a substituted 2-keto-piperazine, and when m is 6 and cyclized, then ~I) 35 typically represents a substituted 2-keto-decahydroquinoxaline; Rl amd R4 independently represent hydrogen, alkyl having from 1 to about 24 carbon atoms, 11~257S5 hydroxyalkyl having from 1 to about 12 carbon atoms, haloaL<yl having from 1 to about 12 carbon atoms, cyanoalkyl having from 2 to about 12 carbon atoms, aminoalkyl or iminoalkyl having from 1 to about 12 carbon toms, ether groups having from 3 to about 18 carbon atoms, hydroxyalkyl ether or cyenoalkyl ether 5 groups having from 4 to about 18 carbon atoms, alkenyl or aralkyl having from 7 to about 14 carbon atoms, alkylene having from 2 to about 7 carbon atoms and optionally containing a phosphite, ester or hindered phenol group; R4 may be oxygen; and, R2 and R3 on the N4-adjacent carbon of the fixed two-carbon bridge 10 independently each represent alkyl having from 1 to about 12 carbon atoms, haloalkyl having from 1 to about 12 carbon atoms, cyanoalkyl having from 2 to about 12 carbon atoms, aminoalkyl or iminoalkyl having from 2 to about 12 carbonatoms, cycloalkyl having from 5 to about 14 carbon atoms, hydroxy-cycloalkyl having from 5 to about 14 carbon atoms, alkenyl and aralkyl having from 7 to about 15 14 carbon atoms, alkylene having from 2 to about 7 carbon atoms and optionally containing a phosphite, ester or hindered phenol group, and which in combination, one with another, represent cycloalkyl naving from 5 to about 14 carbon atoms atleast four of which are cyclized and optionally containing a keto, ester, amide,ether, thio or hydroxy group.
- 20 When it is desired to prepare a compound having a substituted alkylene group in the var;able length bridge of the above-identified structural formula (1), the compound may be represented by a structural formula selected from ~ R8 ~Rl o R6~ ~R -- (II), hnd R7~ -- --- (III) wherein n represents an integer in the range from 0 to about 6; so when n is ~ then 25 (II) and (IIl) represent substituted 2-keto-piperazine, and when n is 4 with the variable length bridge cyclized, then (II) and (III) represent 2-keto-decahydroquin-oxaline; and, R5, R69 R7, R8 in the variable length bridge have the same connotation as R2 and R3 in (I) hereinabove, and additionally may be H, except that R5 and R6 are different if either is H; R2, R3 may be cyclizable, as may be R5, R6, 30 R7, R8; and, if cyclized, the cyclic substituents may be the same or different.
~l125755 Illustrative of the type of substituents that provide effective stabilizat-ion in the above-identified 2-keto-diazacycloalkanes Il and III are:
where Rl and/or R4 is alkyl, examples are methyl, ethyl, n-propyl, n-butyl, t-butyl, n-hexyl, n~ctyl, 2-ethylhexyl, n-decyl, n-tetradecyl, n-octyldecyl, 5 and the like;
where R1 and/or R4 is hydroxyalkyl, examples are 2-hydroxyethyl, 2-hydroxypropyl, 3-hydroxypropyl, 2-hydroxybutyl, 6-hydroxyhexyl, 8-hydroxyoctyl, and the like;
where Rl and/or R4 is haloalkyl, examples are 2-chloroethyl, 2-10 bromoethyl, 2-fluoroethyl, 2-chlorobutyl, 4-chlorobutyl, 2-chloroethylhexyl, and the like;
where Rl and/or R4 is cyanoalkyl, examples are 2-cyanoethyl, 3-cyanopropyl, 4-cyanobutyl, 8-cyanooctyl, and the like;
where Rl and R4 is aminoalkyl or iminoalkyl, examples are 2-15 aminoethyl, 3-aminopropyl, 4-aminobutyl, 6-aminohexyl, 2-methyl-2-aminoethyl, and the like;
where R1 and R4 is ether, examples are methoxyethyl, ethoxyethyl, ethoxypropyl, octyloxyethyl, phenoxyethyl, ~methylphenoxypropyl, and the like;
when R is hydroxyalkylether or cyanoallcyl ether, examples are 2-hydroxyethyloxa-20 ethyl, p~2-hydroxypropyl)-phenyloxapropyl, 4-hydroxybutyloxahexyl, 2-cyanoethyl-oxaethyly 2-hydroxyethyl~i(oxaethyl), and the like;
for R2, R3, R5, R6, R7, and R8, examples are methyl, ethyl, propyl, n-butyl, isobutyl, n-hexyl, 2-ethylheptyl, n-decyl, and where the substituents arecyclizable, cyclopentyl, methylcyclopentyl, cyclohexyl, methylcyclonexyl, dimethyl 25 cycloheptyl, piperidyl, 2-2',6-6'-tetramethyl piperidyl) and the like.
Examples of specific substituted mono-keto-diazacycloalkan-2-ones derived from compounds prepared by the syntheses of this invention, wherein the N4-adjacent C atom of the fixed two carbon bridge has two substituents which maybe cyclizable, are:
(a) diazamonocycloalkan-2-ones having a total of more - than four substituents on the diaza ring, for example, 3,3,5,5,6-pentaalkyl-1,4-piperazin-2-one;
(b) trans-1,4-diazabicycloalkan-2-ones for example, trans-3,3-dialkyl-decahydroquinoxalin-2-one; and (c) mono keto-diazatricycloalkan-2-ones, for example, 3,3-t ~, ~ '-di-tert-butylamine) decahydroquinoxalin-2-one.
The more preferred substituted 2-keto-1,4-diazacycloalkane compounds are those wherein: R1 and/or ~4 is selected from the group consisting of alkyl having from 4 to 18 carbon atoms, benzyl, cyclohexylmethyl, hydroxyalkyl ha~/ingfrom 1 to about 6 carbon atoms, hydroxyalkyl ether having from 4 to about 12 5 carbon atoms, cyanoalkyl having from 2 to about 6 carbon atoms, and aminoalkylhaving from 1 to about 6 carbon atoms, R2, R3, R5, R6, R7 and R8 are selected from the group consisting of alkyl having from 1 to about 12 carbon atoms, and polymethylene having from 5 to 6 carbon atoms which are cyclizable; only R2, R3 may be cyclized, or R2, R3 and R5, R6 may be cyclized; and if R2, R3, and R5, R610 are each cyclized, the cyclic substituents are different; and n is a numeral in the range from 4 to about 6 when the methylene groups are cyclized.
Examples of the aforespecified more preferred substituted mono-keto-diazaaL'can-2-ones are:
N4-( ~-hydroxyethyl)-3,3,6-trimel:hyl-piperazin-2-one;
15 N4-( ~-hydroxyethyl) 3,3-pentamethylene-5,5-dimethylpiperazin-2-one;
N4-( ~-hydroxyethyl)3,3,6-trimethyl-diazepin-2-one;
N4-( B-hydroxyethyl) 3,3,6,6-tetramethyl-diazepin-2-one;
N4~ ~-hydroxyethyl) 3,3-pentamethylene-5,5-hexamethylene-diazepin-2-one;
N4-( ~-hydroxyethyl) 3,3-pentamethylene-diazepin-2-one;
20 N4-( ~-hydroxyethyl) 3,3,5,5,7,7-hexamethyl-diazepin-2-one;
N4-( ~-hydroxyethyl~3,3-pentamethylene-5,5,7,7-tetramethyl-diazepin-2-one;
N4~ ~-hydroxyeth~1)3,3-dimethyl-5,5-pentamethylene-piperazin-2-one;
N4~ ~B-hydroxyethyl)3,3,6,6-tetraethyl-5,5-pentamethylene-di~zepin-2-one;
N4-( ~-hydroxyethyl) 3,3-dimethyl-5,6-tetramethylene-diazeine-2-one;
25 N4-t ~-hydroxyethyl) 3,3,5,5-tetramethyl-6,7-tetramethylene-diazepin-2-one;
cis-3,3-dimethyl-decahydroquinoxalin-2-one;
cis-3,3-pentamethylene~ecahydroquinoxalin-2-one;
cis-Nl-(3',5'di-t-butyl-4-hydroxybenzyl)3,3-dimethyl-decahydroquinoxalin-2-one);
trans-Nl-t3',5'-di-t-butyl-4-hydroxybenzyl)3,3,-dimethyl-decahydroquinoxalin-30 2-one;
1,4-butane-bis [N1-(3,3-dimethyl-decahydroquinoxalin-2-one~;
trans-1,6-hexanediol-bis [N -(3,3-dimethyl-decahydroquinoxaline-2-one)di~arboxylat~;
trans-1,6-hexan-bis LN -(3,3-pentamethylene-decahydroquinoxalin-2-one)di-carboxylate];
and, trans-N -carbobutoxy-3,3-dimethyl~decahydroquinoxalin-2-one.
1~25755 Most preferred substituted mono-keto-1,4-diazaalkan-2-ones are:
Nl-dodecyl-3,3,5,5-tetramethyl-2-piperazinone, N -t-octyl-3,3,5,5-tetramethyl-2-piperazinone;
1,2-ethane-bis-(N'-3,3,5,5-tetramethyl-2-piperazinone, N -t-octyl-3,3,6,6-tetramethyl-2-piperazinone, N1-phenyl-3,3,5,5-tetramethyl-2-piperazinone, Nl-t-butyl-3,3-dimethyl-5,5-pentamethylene-2-piperazinone;
Nl-butyl-3,3,5,5,7-pentamethyl-1,4-diazepin-2-one, trans-3,3-pentamethylenedecahydroquinoxalin-2-one, trans-3,3-dimethyl-decahydroquinoxalin-2-one, trans-3,3-dimethyl-~ hydroxyethyl-decahydroquinoxalin-2-one:
trans Nl-dodecyl-3,3-dimethyl-decahydroquinoxalin-2-one;
trans-Nl-benzyl-3,3-dimethyl-decahydroquinoxalin-2-one, trans-Nl-dodecyl-3,3-pentamethylene-decahydroquinoxalin-2-one;
trans Nl-3,3-pentamethylene-decahydroquinoxalin-2-one;
trans-3,3-dimethyl-N -~-hydroxyethyl-decahydroquinoxalin-2-one.
It will no~ be evident that many of the substituents identified hereinabove. may not be made directly by the syntheses of this invention, but by additional steps after having formed the substituted 2-keto-1,4-diazacycloalkane.
These additional steps are well known to those skilled in the art, and do not require detailed description herein.
In particular, dimers and bis compounds of substituted 2-keto-1,4-diazacycloalkanes can be prepared by known methods, once the desired 2-keto-1,4-diazacycloalkane is obtained by a chosen synthesis.
Reaction of Trans-1,2-diaminocycloalkane with Cyanohydrin in Aqueous Medium (Synthesis ~B"):
As stated hereinbefore, the Bindler reference U.S. Patent No. 2,920,077 taught that cis-1,2-diaminocyclo-hexane reacts with acetone cyanohydrin to give cis-3,3-dimethyl-decahydroquinoxalin-2-one (also identified as 3,3-dimethvl-5,6-tetramethylene-2-ketopiperazine~ which melts at 165-166C, but that trans-1,2-diaminocyclohexane behaves differently. Nevertheless it has now been found that trans-1,2-diaminocyclohexane reacts with various ~-hydroxy fatty acid nitriles and are cyclized to yield a 1,4-diazacyclo-alkane reaction product. Generally useful are the cyano-hydrins of aliphatic, araliphatic or cycloaliphatic carbonyl llZ~75~
g compounds whic~ cyclize forming a fixed two-carbon bridge between the Nl and N4 atoms of the diaza ring. Preferred are formaldehyde cyanohydrin, acetaldehyde cyanohydrin, hydro-cinnamaldehyde cyanohydrin, acetone cyanohydrin, methyl ethyl ketone cyanohydrin, cyclohexanone cyanohydrin and the like.
The reaction is carried out by adding a pre-selected cyanohydrin at room temperature dropwise in~ a solution of trans-1,2-diaminocyclohexaine in water. The mixture is stirred and gradually heated to a temperature in the range from about 80C to about 100C at ambient pressure, until the reaction is completed. The product is recovered by removing the aqueous phase. The product may be solid, semisolid or liquid is generally insoluble in the aqueous phase, and is usually visible as a separate organic phase.
The following example ~e~ves to illustrate the invention. Where not otherwise stated, parts are given as parts by weight and the temperatures in degrees centi-grade.
Example 1 Preparation of trans-3,3-dimethyl-1,4-decahydro-quinoxalin-2-one by synthesis "B": ;
H
~ N CH3 _ A mixture of cis and trans isomers of 1,2-diaminocyclohexæne are dissolved in 500 ml water in a 3-necked flask, and acetone cyanohydrin was slowly added over a period of 45 mins. The mixture was stirred for an additional hour at room temperature, then warmed to 90-95C
and maintained at that temperature for 20 hrs. The reaction mixture was then cooled, filtered and the water removed from the filtrate. crystals obtained by recrystallization from acetone were found to be the trans isomer of 3,3-dimethyl-decahydroquinoxalin-2-one. The melting point of the crystals was about 218.5-219.5C.
ll~S~7~5 Elemental analysis calculated: 65.9~ 15.37Y~, 9.95% H.
Analysis found: 66.23y~, 15.53/~, 20.06/~.
-
It is known that 4,4,6,6-tetramethyl-1,5-diazacycloheptan-2-one may be prepared by a Schmidt's rearrangement of a six-membered ring with sodium azide (see German Patent Number 2,428,877) but there is no known manner of similarl~ arriving at a six membered 1,4-diaza ring with an N -adjacent carbonyl, -- 1 -- ~
1125'755 - la -It is known 1,4-diaza(3,3,5,5)-dipentamethylene-2-one may be prepared, starting with cyclohexanone by cyclization of bis(l-cyanocyclohexyl)amine, reducing with lithium aluminum hydride to form 1,4-diaza(2,2,5,5)-dipentamethylene-2-imino, treating with acetic anhydride and heating with hydrochloric acid. This is set out in greater detail in an article by Helmut Egg in Monatshefto fur Chemie 106, 1167-1173 (1975). However, starting with acetone instead of cyclohexanone, the reactions do not proceed in an analogous manner to give 3,3,5,5-tetramethyl-piperazin~2-one. This Egg reference teaches substituted piperazines wherein each symmetrical N4-adjacent carbon is part of a six membered ring and the cyclic substituent on each N4-adjacent carbon is always the 11;~575S
same. A single cyclic substituent on the N4-adjacent C atom oî the fixed two-carbon bridge cannot be prepared by following the techniques of Egg.
Cis-3,3-dimethyl-decahydroquinoxalin-2-one has been prepared by cis-1,2-diaminocyclohexane, and it is disclosed that the cis-compounds are valuable 5 intermediates for the production of pharmaceuticals, textile auxili~ry products and synthetic materials. This reference states that the trans-1,2-diaminocyclohexaneis converted, with excess chloracetic acid, or with salts thereof, into 1,2-diaminocyclohexane-N,N'-tetraacetic acid, which is quite unlike the behavior of the cis starting material. The cis-2-keto-1,4-diazacycloalkane is prep~red by reacting 10 an aqueous solution of cis-1,2-diaminocyclohexane with acetone cyanohydrin, and heating the reaction solution to dryness. The reference does not teach formationof a trans-5,6-polyalkylene-2-keto-diazacycloalkane, and there is no suggestion as to how it could be made. In fact, it is to be understood that the trans-2-keto-1,4-diazacycloalkane cannot be made, since Bindler states that cis-1,2-diaminocyclo-15 hexane behaves differently from trans-1,2-diaminocyclohexane; the positioning of the two primary amine moieties imparts distinctly different properties to the isomers. This dfference, and particularly the essential difference in cyclization behavior of the primary amine moieties, is used to advantage in the separation of the isomers. The cis isomer cyclizes and complexes with Ni and Cu; the trans 20 isomer does not. Nevertheless we have found that trans-2-keto-1,4-diazacyclohex-ane can now be formed in a manner analogous to that in which the cis-2-keto-1,4-diazacyclohexane is formed.
Following the teachings of Bindler, ethylene diamine may be substituted for cyclohexanediamine, and 3,3-dimethyl-2-keto-piperazine is obtained. However,25 when a substituted ethylene diamine is used, the substituents appear on the No. 6 carbon of the diaza ring. For example with 1,2-propane diamine, 3,3,6-trimethyl-2-keto-piperazine is formed; and with 2-methyl-1,2-propane diamine the compound obtained is 3,3,6,6--tetramethyl-2-keto-piperazine. No. 6-substituted and 3-substituted carbons are not symmetrical carbon atoms about the same N-adjacent 30 atom in the diaza ring (hereinafter referred to as "symmetrical N-adjacent C
atoms"). These compounds are quite unlike the novel compounds claimed.
Moreover, 3,3,6,6-tetraalkyl substituted diazacycloalkan-2-ones, in which the substituents are not on symmetrical N-adjacent C atoms, are selatively ineffective UV stabilizers, confirming my experience that the more substituents on symmetri-35 cai N-adjacent C atoms, the better the stabilization effect.
It is known that 2,2,4-trimethyl-tetrahydroquinoline can be hydrogenat-ed to form a mixture of cis and trans 2,2,4-trimethyldecahydroquinoline, and, ingeneral, the trans isomer is the major constituent. However, 2,2-dimethyl-tetrahydroquinoxaline is not hydrogenated in an analogous manner.
_ 3 _ ~1~57SS
It is to the problem of synthesizing polysub-stituted 2-keto-1,4-diazacycloalkanes, efficiently and economically, so that they can be manufactured for com-mercial use, that this invention is directed.
It has been discovered that polysubstituted 2-keto-1,4-diazacycloalkanes may be prepared from readily available starting materials, in simple, conventional apparatus, without the high risks attendant upon using hydrogen cyanide. This may be done by any of several novel syntheses.
A. A novel synthesis has been discovered wherein cis-3,3-dialkyl-3,4-dihydroquinoxalin-2-one is hydro-genated in the presence of a suitable hydrogenation catalyst, at elevated temperature and pressure, to yield a cis-3,3-di-alkyl-decahydroquinoxalin-2-one.
B. A novel synthesis has been discovered wherein trans-1,2-diaminocyclohexane is reacted with acetone cyano-hydrin in the presence of water to yield trans-3,3-dimethyl-decahydroquinoxalin-2-one.
C. A novel synthesis has been discovered (herein-after referred to as "the cyanohydrin synthesis"), wherein a cyclic or acyclic 1,2-diamine is reacted with cyclic or acyclic cyanohydrins in the presence of a suitable organic solvent in the presence of aqueous ~aOH at ambient temperature and pressure, in the presence of an "onium salt"
(defined hereinafter) catalyst in conjunction with a halo-form, to yield a polysubstituted 2-keto-1,4-diazacycloalkane.
D. A novel synthesis has been discovered (herein-after referred to as "the ketoform synthesis") wherein a preselected 1,2-diamine is reacted with a saturated acyclic or cyclic monoketone, and, a haloform, in the presence of (i) an onium salt catalyst (ii) an organic solvent, and (iii) aqueous alkali.
The present invention is more particularly concerned with synthesis B.
, ,, `` 1125~55 The basic structure of the compounds prepared by the syntheses described herein, is a polysubstituted (hereafter also referred to as "substituted" for brevity) 2-keto-1,4-diazacycloalkane having (a) a fixed two-carbon bridge between the two N atoms (the Nl and N4 atoms) of the diaza ring, the remaining portion of the ring having a variable length bridge of two or more carbon atoms, (b) an Nl-adjacent carbonyl in the fixed two-carbon bridge, and (c) at least the N - adjacent carbon of the fixed two-carbon bridge has two substituents (hence "polysubstituted"), which may be cyclizable, that is, form a cyclic substituent. These compounds which may be monocyclic, or with cyclizable substituents, may be bicyclic or tricyclic, are particularly useful as UV light stabilizers in substantially 1125~55 colo~less organic materials. The compounds may also form dimers and bis-compounds. The diaza ring of the basic structure may have from 6 to 9 ring members, more preferably from 6 to 8 ring members, and most preferably from 6 to 7 ring members.
These substituted 2-keto-1,4-diazacycloalkanes characteristically have two substituents, which may be cyclizable, on the N4-adjacent C atom of the fixed two-carbon bridge. They are particularly useful as UV light stabilizers in compositions subjected to UV light degradation. As stabilizers they are used in the range from about 0.01 to about 5 parts by weight, and preferably from about 0.1 to 10 about 1.0 part per one hundred parts (phr) of organic material subject to UV light.
These materials may be low or high molecular weight materials, and particularly include homopolymers, copolymers and mixtures thereof. Examples of materials that can be stabilized against degradtion due to UV light are oils; monomers, particularly , ~ -olefinically unsaturated monomers such as acrylates, dines, vinyl 15 nitriles, and the like; and other relatively lower molecular weight materials than synthetic resinous polymers, such as alcohols, aldehydes, and the like. Exflmples of known mater;als which can be stabili~ed with polysubstituted 2-keto-1,4~iazacy-cloalkanes are natural rubber, synthetic rubbers such as cis-polystyrene, polyacryl-onitrile, polymethacrylates, polycarbonates, varnish, phenol-formaldehyde resins, 20 polyepoxides, polyesters, and polyolefin homo and copolymers such as polyethylene, polypropylene, ethylene-propylene polymers, ethylene-propylenediene polymers, ethyl-vinyl acetate polymers, and the like. The substituted 2-keto-1,4~iazacyclo-alkanes can also be used to stabilize mixtures and blends of polymeric materialssuch as ABS resin blends, PVC and polymethacrylate blends, and blends of 25 polyolefin homopolymers and copolymers such as blends of polypropylene in epdm polymers.
The 2-keto-1,4-diazacycloalkanes prepared by the syntheses of this invention have the structural formula: R1 2)m ~ R -- -- (I) 30 wherein, m represents an integer in ~he range from 2 to 7, being the number of methylene groups fol ming a bridge of variable length, and some of which groups (a) together with the carbons to which they are bound, may form a cyclopentyl, cyclohexyl or cycloheptyl endo ring, or (b) be substituted; when m is 2 then (I)represents a substituted 2-keto-piperazine, and when m is 6 and cyclized, then ~I) 35 typically represents a substituted 2-keto-decahydroquinoxaline; Rl amd R4 independently represent hydrogen, alkyl having from 1 to about 24 carbon atoms, 11~257S5 hydroxyalkyl having from 1 to about 12 carbon atoms, haloaL<yl having from 1 to about 12 carbon atoms, cyanoalkyl having from 2 to about 12 carbon atoms, aminoalkyl or iminoalkyl having from 1 to about 12 carbon toms, ether groups having from 3 to about 18 carbon atoms, hydroxyalkyl ether or cyenoalkyl ether 5 groups having from 4 to about 18 carbon atoms, alkenyl or aralkyl having from 7 to about 14 carbon atoms, alkylene having from 2 to about 7 carbon atoms and optionally containing a phosphite, ester or hindered phenol group; R4 may be oxygen; and, R2 and R3 on the N4-adjacent carbon of the fixed two-carbon bridge 10 independently each represent alkyl having from 1 to about 12 carbon atoms, haloalkyl having from 1 to about 12 carbon atoms, cyanoalkyl having from 2 to about 12 carbon atoms, aminoalkyl or iminoalkyl having from 2 to about 12 carbonatoms, cycloalkyl having from 5 to about 14 carbon atoms, hydroxy-cycloalkyl having from 5 to about 14 carbon atoms, alkenyl and aralkyl having from 7 to about 15 14 carbon atoms, alkylene having from 2 to about 7 carbon atoms and optionally containing a phosphite, ester or hindered phenol group, and which in combination, one with another, represent cycloalkyl naving from 5 to about 14 carbon atoms atleast four of which are cyclized and optionally containing a keto, ester, amide,ether, thio or hydroxy group.
- 20 When it is desired to prepare a compound having a substituted alkylene group in the var;able length bridge of the above-identified structural formula (1), the compound may be represented by a structural formula selected from ~ R8 ~Rl o R6~ ~R -- (II), hnd R7~ -- --- (III) wherein n represents an integer in the range from 0 to about 6; so when n is ~ then 25 (II) and (IIl) represent substituted 2-keto-piperazine, and when n is 4 with the variable length bridge cyclized, then (II) and (III) represent 2-keto-decahydroquin-oxaline; and, R5, R69 R7, R8 in the variable length bridge have the same connotation as R2 and R3 in (I) hereinabove, and additionally may be H, except that R5 and R6 are different if either is H; R2, R3 may be cyclizable, as may be R5, R6, 30 R7, R8; and, if cyclized, the cyclic substituents may be the same or different.
~l125755 Illustrative of the type of substituents that provide effective stabilizat-ion in the above-identified 2-keto-diazacycloalkanes Il and III are:
where Rl and/or R4 is alkyl, examples are methyl, ethyl, n-propyl, n-butyl, t-butyl, n-hexyl, n~ctyl, 2-ethylhexyl, n-decyl, n-tetradecyl, n-octyldecyl, 5 and the like;
where R1 and/or R4 is hydroxyalkyl, examples are 2-hydroxyethyl, 2-hydroxypropyl, 3-hydroxypropyl, 2-hydroxybutyl, 6-hydroxyhexyl, 8-hydroxyoctyl, and the like;
where Rl and/or R4 is haloalkyl, examples are 2-chloroethyl, 2-10 bromoethyl, 2-fluoroethyl, 2-chlorobutyl, 4-chlorobutyl, 2-chloroethylhexyl, and the like;
where Rl and/or R4 is cyanoalkyl, examples are 2-cyanoethyl, 3-cyanopropyl, 4-cyanobutyl, 8-cyanooctyl, and the like;
where Rl and R4 is aminoalkyl or iminoalkyl, examples are 2-15 aminoethyl, 3-aminopropyl, 4-aminobutyl, 6-aminohexyl, 2-methyl-2-aminoethyl, and the like;
where R1 and R4 is ether, examples are methoxyethyl, ethoxyethyl, ethoxypropyl, octyloxyethyl, phenoxyethyl, ~methylphenoxypropyl, and the like;
when R is hydroxyalkylether or cyanoallcyl ether, examples are 2-hydroxyethyloxa-20 ethyl, p~2-hydroxypropyl)-phenyloxapropyl, 4-hydroxybutyloxahexyl, 2-cyanoethyl-oxaethyly 2-hydroxyethyl~i(oxaethyl), and the like;
for R2, R3, R5, R6, R7, and R8, examples are methyl, ethyl, propyl, n-butyl, isobutyl, n-hexyl, 2-ethylheptyl, n-decyl, and where the substituents arecyclizable, cyclopentyl, methylcyclopentyl, cyclohexyl, methylcyclonexyl, dimethyl 25 cycloheptyl, piperidyl, 2-2',6-6'-tetramethyl piperidyl) and the like.
Examples of specific substituted mono-keto-diazacycloalkan-2-ones derived from compounds prepared by the syntheses of this invention, wherein the N4-adjacent C atom of the fixed two carbon bridge has two substituents which maybe cyclizable, are:
(a) diazamonocycloalkan-2-ones having a total of more - than four substituents on the diaza ring, for example, 3,3,5,5,6-pentaalkyl-1,4-piperazin-2-one;
(b) trans-1,4-diazabicycloalkan-2-ones for example, trans-3,3-dialkyl-decahydroquinoxalin-2-one; and (c) mono keto-diazatricycloalkan-2-ones, for example, 3,3-t ~, ~ '-di-tert-butylamine) decahydroquinoxalin-2-one.
The more preferred substituted 2-keto-1,4-diazacycloalkane compounds are those wherein: R1 and/or ~4 is selected from the group consisting of alkyl having from 4 to 18 carbon atoms, benzyl, cyclohexylmethyl, hydroxyalkyl ha~/ingfrom 1 to about 6 carbon atoms, hydroxyalkyl ether having from 4 to about 12 5 carbon atoms, cyanoalkyl having from 2 to about 6 carbon atoms, and aminoalkylhaving from 1 to about 6 carbon atoms, R2, R3, R5, R6, R7 and R8 are selected from the group consisting of alkyl having from 1 to about 12 carbon atoms, and polymethylene having from 5 to 6 carbon atoms which are cyclizable; only R2, R3 may be cyclized, or R2, R3 and R5, R6 may be cyclized; and if R2, R3, and R5, R610 are each cyclized, the cyclic substituents are different; and n is a numeral in the range from 4 to about 6 when the methylene groups are cyclized.
Examples of the aforespecified more preferred substituted mono-keto-diazaaL'can-2-ones are:
N4-( ~-hydroxyethyl)-3,3,6-trimel:hyl-piperazin-2-one;
15 N4-( ~-hydroxyethyl) 3,3-pentamethylene-5,5-dimethylpiperazin-2-one;
N4-( ~-hydroxyethyl)3,3,6-trimethyl-diazepin-2-one;
N4-( B-hydroxyethyl) 3,3,6,6-tetramethyl-diazepin-2-one;
N4~ ~-hydroxyethyl) 3,3-pentamethylene-5,5-hexamethylene-diazepin-2-one;
N4-( ~-hydroxyethyl) 3,3-pentamethylene-diazepin-2-one;
20 N4-( ~-hydroxyethyl) 3,3,5,5,7,7-hexamethyl-diazepin-2-one;
N4-( ~-hydroxyethyl~3,3-pentamethylene-5,5,7,7-tetramethyl-diazepin-2-one;
N4~ ~-hydroxyeth~1)3,3-dimethyl-5,5-pentamethylene-piperazin-2-one;
N4~ ~B-hydroxyethyl)3,3,6,6-tetraethyl-5,5-pentamethylene-di~zepin-2-one;
N4-( ~-hydroxyethyl) 3,3-dimethyl-5,6-tetramethylene-diazeine-2-one;
25 N4-t ~-hydroxyethyl) 3,3,5,5-tetramethyl-6,7-tetramethylene-diazepin-2-one;
cis-3,3-dimethyl-decahydroquinoxalin-2-one;
cis-3,3-pentamethylene~ecahydroquinoxalin-2-one;
cis-Nl-(3',5'di-t-butyl-4-hydroxybenzyl)3,3-dimethyl-decahydroquinoxalin-2-one);
trans-Nl-t3',5'-di-t-butyl-4-hydroxybenzyl)3,3,-dimethyl-decahydroquinoxalin-30 2-one;
1,4-butane-bis [N1-(3,3-dimethyl-decahydroquinoxalin-2-one~;
trans-1,6-hexanediol-bis [N -(3,3-dimethyl-decahydroquinoxaline-2-one)di~arboxylat~;
trans-1,6-hexan-bis LN -(3,3-pentamethylene-decahydroquinoxalin-2-one)di-carboxylate];
and, trans-N -carbobutoxy-3,3-dimethyl~decahydroquinoxalin-2-one.
1~25755 Most preferred substituted mono-keto-1,4-diazaalkan-2-ones are:
Nl-dodecyl-3,3,5,5-tetramethyl-2-piperazinone, N -t-octyl-3,3,5,5-tetramethyl-2-piperazinone;
1,2-ethane-bis-(N'-3,3,5,5-tetramethyl-2-piperazinone, N -t-octyl-3,3,6,6-tetramethyl-2-piperazinone, N1-phenyl-3,3,5,5-tetramethyl-2-piperazinone, Nl-t-butyl-3,3-dimethyl-5,5-pentamethylene-2-piperazinone;
Nl-butyl-3,3,5,5,7-pentamethyl-1,4-diazepin-2-one, trans-3,3-pentamethylenedecahydroquinoxalin-2-one, trans-3,3-dimethyl-decahydroquinoxalin-2-one, trans-3,3-dimethyl-~ hydroxyethyl-decahydroquinoxalin-2-one:
trans Nl-dodecyl-3,3-dimethyl-decahydroquinoxalin-2-one;
trans-Nl-benzyl-3,3-dimethyl-decahydroquinoxalin-2-one, trans-Nl-dodecyl-3,3-pentamethylene-decahydroquinoxalin-2-one;
trans Nl-3,3-pentamethylene-decahydroquinoxalin-2-one;
trans-3,3-dimethyl-N -~-hydroxyethyl-decahydroquinoxalin-2-one.
It will no~ be evident that many of the substituents identified hereinabove. may not be made directly by the syntheses of this invention, but by additional steps after having formed the substituted 2-keto-1,4-diazacycloalkane.
These additional steps are well known to those skilled in the art, and do not require detailed description herein.
In particular, dimers and bis compounds of substituted 2-keto-1,4-diazacycloalkanes can be prepared by known methods, once the desired 2-keto-1,4-diazacycloalkane is obtained by a chosen synthesis.
Reaction of Trans-1,2-diaminocycloalkane with Cyanohydrin in Aqueous Medium (Synthesis ~B"):
As stated hereinbefore, the Bindler reference U.S. Patent No. 2,920,077 taught that cis-1,2-diaminocyclo-hexane reacts with acetone cyanohydrin to give cis-3,3-dimethyl-decahydroquinoxalin-2-one (also identified as 3,3-dimethvl-5,6-tetramethylene-2-ketopiperazine~ which melts at 165-166C, but that trans-1,2-diaminocyclohexane behaves differently. Nevertheless it has now been found that trans-1,2-diaminocyclohexane reacts with various ~-hydroxy fatty acid nitriles and are cyclized to yield a 1,4-diazacyclo-alkane reaction product. Generally useful are the cyano-hydrins of aliphatic, araliphatic or cycloaliphatic carbonyl llZ~75~
g compounds whic~ cyclize forming a fixed two-carbon bridge between the Nl and N4 atoms of the diaza ring. Preferred are formaldehyde cyanohydrin, acetaldehyde cyanohydrin, hydro-cinnamaldehyde cyanohydrin, acetone cyanohydrin, methyl ethyl ketone cyanohydrin, cyclohexanone cyanohydrin and the like.
The reaction is carried out by adding a pre-selected cyanohydrin at room temperature dropwise in~ a solution of trans-1,2-diaminocyclohexaine in water. The mixture is stirred and gradually heated to a temperature in the range from about 80C to about 100C at ambient pressure, until the reaction is completed. The product is recovered by removing the aqueous phase. The product may be solid, semisolid or liquid is generally insoluble in the aqueous phase, and is usually visible as a separate organic phase.
The following example ~e~ves to illustrate the invention. Where not otherwise stated, parts are given as parts by weight and the temperatures in degrees centi-grade.
Example 1 Preparation of trans-3,3-dimethyl-1,4-decahydro-quinoxalin-2-one by synthesis "B": ;
H
~ N CH3 _ A mixture of cis and trans isomers of 1,2-diaminocyclohexæne are dissolved in 500 ml water in a 3-necked flask, and acetone cyanohydrin was slowly added over a period of 45 mins. The mixture was stirred for an additional hour at room temperature, then warmed to 90-95C
and maintained at that temperature for 20 hrs. The reaction mixture was then cooled, filtered and the water removed from the filtrate. crystals obtained by recrystallization from acetone were found to be the trans isomer of 3,3-dimethyl-decahydroquinoxalin-2-one. The melting point of the crystals was about 218.5-219.5C.
ll~S~7~5 Elemental analysis calculated: 65.9~ 15.37Y~, 9.95% H.
Analysis found: 66.23y~, 15.53/~, 20.06/~.
-
Claims (6)
1. A method for preparing a polysubstituted 2-keto-1,4-diazacycloalkane trans-isomer, comprising dissolving a trans-1,2-diaminocycloalkane in water, adding a predetermined amount of an .alpha.-hydroxy fatty acid nitrile selected from the group consisting of aliphatic cyanohydrins, araliphatic cyanohydrins, and cycloaliphatic cyanohydrins to form an aqueous mixture, heating said mixture to cause reactants in said mixture to form said trans-isomer, and recovering said trans-isomer from said mixture.
2. The method of claim 1, wherein said trans-isomer is a trans-3,3-dialkyl-1,4-diazacycloalkane, said trans-1,2-diaminocycloalkane is trans-1,2-diamino-cyclohexane, and said .alpha.-hydroxy fatty acid nitrile is an aliphatic cyanohydrin.
3. The method of claim 2, wherein said trans-1,2-diaminocyclohexane is mixed with cis-1,2-diaminocyclo-hexane, and said aliphatic cyanohydrin is acetone cyano-hydrin.
4. The method of claim 1, wherein said heating is to a temperature of about 80°C to about 100°C.
5. The method of claim 4, wherein said heating is at ambient pressure.
6. The method of claim 1, 4 or 5, wherein said nitrile is selected from the group consisting of form-aldehyde cyanohydrin, acetaldehyde cyanohydrin, hydro-cinnamaldehyde cyanohydrin, acetone cyanohydrin, methyl ethyl ketone cyanohydrin and cyclohexanone cyanohydrin.
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| CA362,476A CA1125755A (en) | 1978-06-19 | 1980-10-15 | Synthesis of 2-keto-1,4-diazacycloalkanes |
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| US916,640 | 1978-06-19 | ||
| US05/916,640 US4167512A (en) | 1977-09-21 | 1978-06-19 | Synthesis of 2-keto-1,4-diazacycloalkanes |
| CA310,371A CA1109867A (en) | 1977-09-21 | 1978-08-30 | Synthesis of 2-keto-1,4-diazacycloalkanes |
| CA362,476A CA1125755A (en) | 1978-06-19 | 1980-10-15 | Synthesis of 2-keto-1,4-diazacycloalkanes |
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