DE1670429A1 - Process for the production of 2-isopropenyl-delta? -Oxazoline - Google Patents

Description

CH3I-iI30: iE ^T ./.3RK3 HÜLS AG
- Patent Department -

Our reference: O.Z. 2171

4370 Mari, February 15, 1957 2063 / B

Verfallron for the production of 2-isopropenyl Λ. -oxazoline

The invention relates to a process for the preparation of the previously not described 2-isopropenyl ~ ^ -oxazoline

ρ
from 2-methyl- ^ -oxazoline.

In the 2-position OC ₁ ß-unsaturated Λ -oxazolines have found considerable interest as monomers and comonomers for the preparation of polymers (French patents 1,385,727, 1,367,518 and German patent 1,067,437). In addition to the unsaturated 2-position substituent, all oxazolines of this type used hitherto for the polymerization have further substituents in the 4-position.

In processes that are not yet part of the state of the art,

2-isopropenyl- Λ -oxazoline, which is unsubstituted in the oxazoline ring, has proven its worth as a starting material for polymerizations and as a copolymerization component. However, its technical use has hitherto stood in the way of the lack of a satisfactory production method.

That for the preparation of 2-alkyl- and 2-aryl- ^ -oxazolinen technically most favorable, from Angew. Ohem. JB (1966), 914 "known Process, the gas phase dehydration of the N "- / j? -Hydroxyäthyl7- -carboxamides, can be based on o (, ß-unsaturated carboxamides, especially the N-ZS-HydroxyäthylJ-methacrylamid, not with transferred with satisfactory success. The unsaturated amide tends to undergo gas phase dehydration conditions

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polymerize, which reduces the yield and the catalyst .lysator quickly inactivated.

The dehydration of F- ^ 2-Hydroxyäthyl7-methacrylamid by Heating in the presence of sulfuric acid and polymerization inhibitors (see German patent specification 1,067,437) also leads not to 2-isopropenyl oxazoline. In this German patent specification only the preparation of 4,4-disubstituted oxazolines is described; in these, however, the cyclization reaction is a consequence strongly favored the "geminal dimethyl effect" (J. Org. Chem. 28: 2759 (1965)). For example, 2,4,4-trimethyl- and 2-tert-butyl-4,4-dimethyl-oxazoline by simply heating of the substituted ethanolamine in question prepared with the carboxylic acid, while unsubstituted for the representation in the ring Oxazoline the conditions of gas phase dehydration are required.

From the French patent 1 385 727 it is still known that oxazolines with a 2-ständi.gen aliphatic Substituents that still have at least one O ^ -hydrogen atom, with one mole of paraformaldehyde in 2- (1'-alkyl ^^ - hydroxyethyl) - -oxazoline can convert. You can do this by splitting off water .Produce oxazolines, which have an OC, ß-unsaturated, 2-position Carry substituents. According to the patent mentioned, these unsaturated oxazolines can also be obtained in one step, by carrying out the reaction with formaldehyde in the presence of acidic catalysts, at the same time from the primary product Water is split off.

However, these known methods have been found in attempts to

2
Production of 2-isopropenyl- Λ -oxazoline is not very productive.

The addition of formaldehyde to 2-ethyl-oxazoline, which is described in Example 6 without any indication of the yield, gives, according to our own investigations, under the specified conditions only 13% of the theory of the intermediate 2- (1 · -Methyl-2 * -hydroxyethyl) -oxazoline. The transfer of the production of 2- * isopropenyl-4,4-dimethyl-4Ä ² -

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-oxazoline from 2-A * thyl-4,4-dimethyl- Λ -oxazoline in one step to the production of 2-isopropenyl-, A -oxazoline proved to be less successful; the oxazoline, which is not substituted in the 4-position, tends to cleave in the acidic reaction medium. When reworking example 20 with 2-ethyl- Δ. --oxazoline as a starting product resulted in only 15 $ of the theory 2-isopro- -wä -oxazoline.

The invention is based on the object of producing 2-isopropenyl- <Δ-oxazoline in a simple manner and with good yields.

This object is achieved according to the invention in that

a) 2-Methyl- ^ -oxazoline with at least the equimolar amount of Parafons dehyd, optionally in GegB " , kind of an inert solvent, converted into 2- (2'- oxazolinyl) allyl alcohol;

b) 2- (2 ■ -oxazolinyl) allyl alcohol in the presence a hydrogenation catalyst to 2- (2'-oxazolinyl) - -propanol- (1) hydrogenated;

c) 2- (2 * -0xazolinyl) -propanol- (1) at temperatures of 100 to 400 ⁰ C ₁ is preferably from 200 to 400 ⁰ C, in the gas phase at reduced pressure of dehydration

catalysts for 2-isopropenyl- & -oxazoline

dehydrated. .

The following formulation s corresponds to the three procedural steps

+ 2H ₂ CO ₁ -H ₂ O

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Go to step A

It is known from French patent specification 1,585,727. that from oxazolines with a 2-position aliphatic substituent which still carries at least one oC hydrogen atom, a monoaddition product can be produced by adding one mole of formaldehyde. It is also known from the same patent that this monoaddition product occurs as an intermediate,

if the reaction of 2-alkyl- Δ- oxazolines with formaldehyde in an acidic medium produces unsaturated oxazolines in one step in the 2-substituent. In the examples of the patent mentioned, the formaldehyde is used in an approximately 10% excess over the equimolar amount. Addition products of more than one molecule of formaldehyde to one molecule of oxazoline are nowhere mentioned.

It has now been found that 2-methyl-Δ «-ozazoline (I) with treatment with excess formaldehyde add 2 moles of formaldehyde to the 2-position methyl group, with tinter simultaneous Elimination of 1 mole of HgO 2- (2'-oxazolinyl) allyl alcohol (II) arises.

The course of the reaction depends on the Meng® of the used Formaldehyde. Assuming amounts of 1 isis to 2 moles per mole of oxazoline a, this creates II, but also a monoad & itlons product • V. When using less than

the molar amount of formaldehyde produced aussoiiließlieli ¥ _e is 2 Me 3 moles of formaldehyde per mole © xasollm β la., 'so ale II major product. The use of m © kr as 5 moles of formaldehyde brings no further improvement with elcn

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To carry out step A, 2-methyl- ^ -oxazoline is reacted with paraformaldehyde, expediently in two to three times the molar amount, at temperatures from 10 to HO ⁰ C, preferably from 40 to 140 ⁰ G. It is advantageous to carry out the reaction in the presence \ of an inert solvent, which may serve simultaneously as entrainer for the water formed during the reaction. Benzene, toluene, ethylbenzene or xylene are particularly suitable.

The addition is recommended to accelerate the course of the reaction of insufficient amounts of a strong organic base, preferably from 0.1 to 0.2.MoI, based on the 2-methyl-. -oxazoline. For example, piperidine and triethylamine are suitable.

The reaction can be carried out in such a way that the components are simply combined and heated. Because of the tendency of paraformaldehyde to sublime, it is advisable to use a limited amount of it first and to add the remaining amount gradually. The catalytically active organic base can also be added in portions.

A stirred vessel with an attached reflux condenser and water separator is expediently chosen as the reaction vessel. The reaction mixture is refluxed therein at least until no more water is produced.

For work-up, the solvent is distilled off and fractionated the residue in vacuo; for further cleaning can II from suitable solvents, e.g. a benzene-mgroin mixture, recrystallized will.

It is expedient "the reaction and distillation in the presence of small amounts of a Polymerisationsinhibitoro _r example from 0.5 weight percent KupferpulYer, duröliauführenv ■■ ';.' .

The course of the reaction on which step A is based is surprising. It was more comparable with knowledge of the Additiüneverhaitras. Compounds with a specification of mete as equi-molar quantities

r -

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Only formaldehyde, the addition of further formaldehyde to the activated methyl or ethylene group with the formation of di- or trihydroxymethyl bonds. Compounds comparable to methyl oxazoline with regard to the reactivity of the 2-methyl group are, for example, quinaldine and 2,4-lutidine. Quinaldine, according to Chemical Abstracts 57 '(1962), 16 555 i, when converted with 4 moles of formaldehyde, in addition to the monoaddition product, forms only ^ -U'-quinolinyl / propanediol-d ^). According to Chemische Technik 9 (1957), 96 (Chemical Abstracts 5 ± (1957) 10 550 c) with excess formaldehyde, 2,4-lutidine yields 2- / 2 '- (4'-methylpyridyl £ 7- propanediol ( 1.3).

• ': ■ ■ · - ^{■■■■■■■:.:} ■

Go to step B -

A selective hydrogenation of the C =C double bond of oxazolines in the 2-position substituent is not known from the literature. It is only known from Chem. Rev. 44 (1949), 459 that the oxazoline ring is stable to mild reducing agents, for example dilute hydrochloric acid / iron powder. Furthermore, from J. Amer. former Soe, 59 (1957), 2 258, Table III, footnote b, known that 2- (liritrophenyl) -oxazolines can be reduced to the amino compounds by catalytic hydrogenation under mild conditions without attacking the oxazoline ring \ apparently - but the reduction is not very smooth. In contrast, ~ In Chem · Ber. 97 (1964), 2 245 stated that, in the case of oxazolines and related heterocycles, catalytic hydrogenation under mild conditions usually leads to ring opening and the formation of amides.

It has now been found that the G = C double bond in 2- (2 ^f - -oxazolinyl) allyl alcohol (II) can be selectively hydrogenated by adding II in a solvent in the presence of a suitable hydrogenation catalyst at low pressures and 3? temperatures hy-

As solvents, for example, methanol, ethanol, iso-

BsglgsäUEeäthylöeter and. -propylestea? in Irage. Suitable catalysts ^ inä ^, | g || ^ | ^ Jier * travel for

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precious metals used, especially platinum and palladium, which are used as a suspension or on carriers. Raney nickel is particularly suitable. The reaction is carried out in a manner known per se, that II is dissolved, the catalyst is added to the solution and, with stirring or shaking, at normal pressure or slightly overpressure (1 to 5 atmospheres) and at temperatures of 0 to 50 ⁰ C hydrogenated. As soon as the calculated amount of hydrogen has approximately been absorbed and the absorption rate is significantly lower, the hydrogenation is stopped. The reaction mixture is freed from the catalyst and the 2- (2 ^t -oxazolinyl) -propanol- (1) (ZII) formed is isolated by distillation.

Go to step C

The introduction of carbon double bonds by catalytic Dehydration of alcohols has long been a part of the state of the art Technology; The dehydration on aluminum oxide has proven particularly successful, Silicates or similar catalysts at elevated temperatures (cf. Ullmann, Encyclopadie der technischen Chemie, Volume 8, Munich - Berlin 1957, page 696).

It has now been found that 2-isopropenyl-oxazoline Zik (IV) can be prepared by reacting 2- (2 ^l -0xazolinyl) -propanol- (i) (III) at temperatures of 100 to 400 ⁰ C, preferably 200 up to 400 ⁰ O, and treated at reduced pressure in the gas phase with dehydration catalysts.

The reaction temperature is best chosen to be above the boiling point of the starting material and the reaction product is at your corresponding reduced pressure. The usual dehydration catalysts are used as catalysts in question, for example silica gel, inorganic silicates, CaO and HgO; is particularly suitable

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We recommend a vertically arranged, tube containing the catalyst. The catalyst must be so coarse be that the vapors of the reacting material are uniform and can flow quickly.

The starting material III is either liquid in the reaction space supplied, whereby it evaporates at the hot contact, or it is supplied immediately in gaseous form, e.g. by distillation. The residence time of the material at the contact may be due to possible Subsequent reactions of the reaction product, e.g. polymerization, not be too long. The throughput should therefore be 0.5 to 5.0 mol, preferably 2.0 to 5.5 moles per hour and liter of contact.

The reaction products are after leaving the contact zone in condensed one or more cooled templates. Your work-up takes place by fractional distillation. It is advisable to remove the water contained in the raw product beforehand by drying, e.g. with solid alkali hydroxide, carbonate or alkaline earth oxide.

The inventive method leads to good yields for 2-Isopropeuyl-Δ oxazoline, a substance not previously described and are difficult to access by conventional methods, as the starting material is 2-methyl Λ -oxazolln zoom sucked that in from the very inexpensive components acetic acid and Ithanolamin is known to be easily accessible.

As stated above, 2-l8opropenyl - ^ - © xafolin is as monomeric starting product for polymerizations and copolymers! - sations commercially exploitable »

Example 1 (step A) - \

A mixture of 554 g (4.5 mol) of 2 »methyl- © xa0 © l! And approximately 59 g (q ', 45 mol) of piperidine is boiled to a boiling point of 192 g (6.4 mol) of paraforfialdehyde and -.2 g of liquid oil-mixed benzene were added dropwise. During the reaction, Vasser und_iii is fed to a separator _ft g # fam | li; ₄ JS & oh 3stüMigeii

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Bring to the boil, add a further 92 g of paraformaldehyde (total 12.5 mol) in each case; with the last addition 39 "g (0.45 mol) of piperidine are also added dropwise. After a reflux time of a total of 12 hours, 34 ml of water have separated out." Main now replaces the reflux condenser with a descending condenser and distills the benzene at atmospheric pressure against End in the water jet vacuum. The residue is fractionated in 4 portions in an oil pump vacuum and yields 392 g (69 ° of theory) of a ^{crude product passing over between 93 to 100 D} C / 1.2! Dorr, the 2- (2 ^l -oxazolinyl) allyl alcohol (II) crystallizes on cooling; it can be purified by redistillation at 97 to 99 ⁰ C / 1.0 Torr or by taking up in benzene and pellets with petroleum ether. Colorless ones are obtained. Papers from the melting ätä point 44 to 46 ⁰ C.

(127) Ber .; C 56.68 f H 7.14 # N 11.02 # Found: C 56.55 # H 7.45 $, N 10.93 1>

Example 2 (step A)

A mixture of 170 g (2 mol) of 2-methyl-oxazoline, 120 g (4 mol) of paraformaldehyde, 17 g (0.2 mol) of piperidine, 2 g of copper powder and 1 liter of benzene is heated with stirring for 1 hour at 70 ⁰ G heated and then refluxed for 4 hours, with water being removed from the system. After another 17 g (0.2 mol) of piperidine have been added, the mixture is heated for a further 8 hours. After working up as in Example 1, 95 g (37.5% of theory) of 2- (2'-oxazolinyl) allyl alcohol are obtained.

Example 3 (step A)

A mixture of 384 g (4.5 mol) 2-methyl-oxazoline, 67 g parafarmaldehyde, 39 g (0.45 mol) piperidine, 2 g copper powder and 1 idter benzene is ^{heated to 50 0} O for 2 hours and then ßend Heated under reflux for 2 hours, with water being removed from the system. After the addition of a further 67 g of paraformaldehyde (a total of 135 g of 4.5 mol) is under again for 2 hours

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Heated to reflux, then 16.5 ml V / water had separated out. The benzene is distilled off and the residue is fractionated in vacuo; you get 2 fractions:

I: b.p. 80 to 91 ° G / 2.5 torr; Yield 118 g, II: b.p. 115 to 120 ° C / 2.5 torr; Yield 140g.

Fraction I delivers 81 g (16 $ 5 of theory) in the redistillation of the monoaddition product of methyl oxazoline and formaldehyde (V), a colorless liquid rom bp 57 to 58 ° C / 0.4 Torr.

G ₅ H ₉ HO ₂ (115) calc .: G 52.16 £ H 7.88 fo Έ 12.17 $

Found: G 52.99 1 » H $ 8.05> N 12.56 1 *

On redistillation, fraction II yields 74 g (13 $> of theory) 2- (2 · -oxazolinyl) -allyl alcohol.

Example 4 (step B);

3P, 7 g (0.24 mol) 2- (2 ^l -0xazolinyl) allyl alcohol are dissolved in 150 ml 99% ethanol and hydrogenated in the presence of 5.0 g Raney-lTickel at 25 ⁰ O and normal pressure. After 5 hours, 85 Φ of the calculated amount of hydrogen has been absorbed. The Raney nickel is centrifuged off, the solvent is distilled off under reduced pressure and the residue is fractionated over a short column. 23.0 g (74 Ψ of theory) is obtained γοΙιθβ 2- (2 -oxazolinyl ^f) -propanol- (i) (Hl), which passes as a colorless liquid 56-62 ⁰ C / 0.05 Torr. The pure compound boils at 65 ^P C / 0.1 Torr;

η ²⁰ - 1
ⁿ D ~ ■ ' 4770. G 55 , 79 G ₆ H ₁₁ ITO ₂ (129.2) Calc .: C. 55 , 87 Found s
- example 5 (step B)

H 8.58 % F 10.85 $ H 8.73 1> Ή 11.04 ? *

6 »5 g (0.445 mol) of 2- (2 ^l -oxazolinyl) -ällyl alcohol are dissolved in 250 ml of ethyl acetate under the conditions of Example 4 la counter · '

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was hydrogenated by 5 »0 g of Raney lfickel. After 4.5 hours, 58 % of the calculated amount of hydrogen has been absorbed. This gives 40.5 g (84 1 "of the theory) of 2-propanol (2 -0xaZQlinyl!). - (i).

Example 6 (step G)

Basic granular AIpO, (HO 418 of the catalyst works Houdry Hüls AG, grain size 4 mm) is placed in a vertical, externally electrically heated quartz tube with an internal diameter of 40 mm and 4 £ Q mm in length arranged in bulk; one from above inserted narrower quartz tube takes 2 thermocouples for that Temperature measurement at two different points on the contact surface. The bulk volume of the catalyst is 460 ml.

The contact is heated for 3 hours at 600 ⁰ C and then cooled in the nitrogen stream tstemperatur the Arbe / 300 ⁰ C. At a pressure of 16 Torr, 2- (2 ^l -Oxazolinyl) -propanol- (1) is allowed to run in from above a dropping funnel at a rate of 1.0 mol / hour and the reaction products are condensed in a methanol / Dry ice chilled template.

As soon as the ratio of input to furnace output has become constant (contact saturation), aliquots of the furnace output are processed to determine the yield. From 193 g (1.5 mol) of 2- (2 ^I- oxazolinyl) propanol- (1) 185 g of discharge from the furnace are obtained; after drying with K ₂ CO, this is subjected to fractional distillation. 106 g (64 # of theory) of 2-isopropenyl-Δ-oxazoline (IV) are obtained as a colorless liquid of i £ p. 52 to 53 ° 0/19 torr; n ² ^ = 1.4768.

C ₆ H ₉ ITO (111.1) Calcd. 5 C 64.84 # H 8.16 # JS 12.60 #. Found: C $ 64.36> H $ 8.64 Ii $ 12.80

Example 7 (step C)

The dehydration of 2- (2 ^l -oxazolinyl) -propanol- (1) under the conditions of Example 5 but at a contact temperature

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of 210 ⁰ C, a pressure of 2 9? prr and a throughput rate of 1.5 mol / hour, delivering 18 $ of iPheorie (based on the use) of 2-Isdpropenyl-oxazoline. $ 43 of the raw material will be recovered unchanged *

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Claims (3)

~ 13 '- QZ 2171 2/15/196 / Pat ent claims , 2 1. Process for the production of ^ -Isopropenyl- ^ -oxazoline, thereby ge Ic e η η ζ e i ο h η et that 2 ' a) 2-methyl- <6 -oxazoline with at least the equimo- lar amount of paraf ormaldehyde * if necessary in Presence of an inert solution agent, in 2- - (2'-Oxazolinyl) -allylailcohol converts j b) 2- (2'-oxazolinyl) ~ allyl alcohol in the presence of a hydrogenation catalyst to 2- (2 ^L - «- 0xazolinyl) - -propanol- (1} ^r hydrogenated, e> the 2- (2 ^l -oxazolinyl.) - propanol- {1) at temperatures from 100 to 400 ⁰ O, preferably from 200 to 400 ⁰ G, in the gas phase at reduced pressure over dehydration catalysts to the 2-isopeelyl ~ Zi -oxazoline dehydrated. 2. The method according to claim 1, characterized in that in step a) 2 to 3 moles of paraformaldehyde per mole of 2-methyl 2
-2i -oxazoline are used. 3. The method according to claim 1 and 2, thereby geke η η »β ic Un et _f 'that step a) is carried out in the presence of different amounts, preferably from 0.1 to 0.2 mol (based on the 2-methyl--oxazoline used) of a strong organic Base executes.