CA1056854A - Hydroxyperoxides - Google Patents
HydroxyperoxidesInfo
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- CA1056854A CA1056854A CA305,787A CA305787A CA1056854A CA 1056854 A CA1056854 A CA 1056854A CA 305787 A CA305787 A CA 305787A CA 1056854 A CA1056854 A CA 1056854A
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Abstract
ABSTRACT OF THE DISCLOSURE
A process for the manufacture of compounds of the general formula (III) (III) wherein R represents an alkyl group of 1 to 6 carbon atoms which comprises oxidising a compound of the formula (II) (II) These hydroperoxides may be further reacted to provide compounds of formula (I) which find use in the brewing industry, for example in the flavouring of beer
A process for the manufacture of compounds of the general formula (III) (III) wherein R represents an alkyl group of 1 to 6 carbon atoms which comprises oxidising a compound of the formula (II) (II) These hydroperoxides may be further reacted to provide compounds of formula (I) which find use in the brewing industry, for example in the flavouring of beer
Description
~35~1~54 This is a division of the copending Canadian application Serial No. 234,837 filed September 5~ 1975.
~ he present invention is concerned with a process for the manu-facture of humulones.
In our copending application 234~837 is described a process for the preparation of compounds of the general formula I
R (I) / ~ ~ H ::
wherein R represents a Cl 6 alkyl group. .::
According to that process the COlllpOUndS of formula I hereinbefore . ;~
are manufactured by oxidising a compound of the general formula ~ R (II) ::
: HO I OH ::. -where~n R has the signi~icance gi~en earlier~ to give a hydroperoxide of the general form~a ..
-- 1 -- .-.. ....
~iS6~354~
l ll R (III) O OH
.
wherein R has the significance given earlier, and subsequently reducing a hydroperoxide of formula III to give a compound of formula I. :~
The compounds of formula I are intermediates for the manufacture of known bitter substances of the general formula ~o T~ (IV) ~ OH
; wherein R has the significance given earlier3 into which they can be converted by isomerisation in a known manner.
The compounds of formula N are of si~nificance in the beverage industry; for example, in the brewing of beer. Thus, for example, in the brewing of beer, the humulone present in the hops tcompound I with R = iso-~butyl) is converted into isohumulone (compound IV with R = isobutyl) during the boiling of the wort with the hops, by which means the pleasantly bitter flavour is imparted to the beer.
' .
: - 2 -~56~3S4 The process described in application 234,837 enables the com-pounds of formula I and, thus9 also the compounds of formula IV, to be manu-factured in good yields~ which hitherto has not been possible (Riedl, Chem.
Berich~e 85, 692-710, 1952).
Apart from the aforementioned isobutyl group~ exa~lples of Cl 6 alkyl groups are: methyl, isopropyl (compound I = cohumulone)~ sec-butyl (compound I = adhumulone), ethyl (compound I = posthumulone), isoamul (com, pound I = prehumulone).
me hydroperoxides of formula III are novel and constitute the present invention.
mus this invention provides in a first aspect a hydroperoxide of formula III
/ ~ OH o l ll R (III) ,~` \ < ;` OH
'. ~ , wherein R represents a Cl to C6 alkyl group.
In a second aspect this invention provides a process for the preparation of a compound of formula III as defined above which comprises oxidising a compound of formula II
HO ~ OH
, 1 .
_ 3 : . , ; ,.... . . .. . . ... ........ ..
~05~5~
by means of elemental oxygen at a temperature of from about 0C to about -50C in the presence of a base and of a polar aprotic solvent.
The process in accordance with the present invention (i.e. the conversion of a compound of formula II into a compound of formula I) is ex-pediently carried out in the presence of a base and a polar aprotic solvent, preferably at a low temperature and especially at a temperature between 0C
and -50C.
As bases there are preferably used very strong bases such as alkali metal alcoholates derived from lower tertiary alkanols (e.g. potassium t-butylate). However, alkali metal hydroxides (e.g. sodium hydroxide or potassium hydroxide) can also be used. The base is preferably used in excess;
for example, in at least a 2-fold excess.
Ihe nature of the polar aprotic solvent is not critical and, in practice, the choice is only limited by the fact that the solidification point thereof must lie below the relatively low temperature at which the process is carried. out. Examples of suitable polar aprotic solvents are ethers (e~g. tetrahydrofuran), di(lower alkoxy)-(lower alkanes) ~e.g. di-methoxyethane)9 amines such as di(lower alkyl)amines (e.g. dimethylamine), nitriles (e.g. acetonitrile), amides such as N,N-di(lower alkyl)amides de-rived from lower aliphatic carboxylic acids (e.g. N,N-dimethylformamide and N,N-dimethylacetamide) phosphoric acid derivatives (e.g. hexamlethylphosphoric acid triamide) etc.
Better yields are obtained by carrying out the process in an anhydrous medium, but the presence of a slight amount (i.e. a small percent-age) of water does not substantially ~mpalr the yields.
The following Examples illustrate the present invention.
ample Preparation and characterisation of the hydroperoxide of formula III (R = i-C ~7):
3 g of desoxy-cohum~lone are dissolved in 700 ml of hexane, ~56~5~
treated with l g of 10% palladium on active carbon (activated by hydrogen treatment) and oxidised at -20 C for 8 hours with air-oxygen. The mixture is filtered, the filtrate concentrated to ca 50 ml under a high vacuum (0.03 mm Hg) and at a maximum temperature of -20C. This solution is chrom-atographed at -18C on silica gel [pre-washed with methanol/concentrated :~:
hydrochloric acid (9:l)] with pentane/ether ~l:l). There is first eluted desoxy-cohumulone, ~hen cohumulone and finally the hydroperoxide of formula III. From the thin-layer chromatogram [silica gel on glass, washed with methanol/concentrated hydrochloric acid (9:l); eluant: hexane/ether (l:l) + 1% (V/V) glacial acetic acid}, the individual fractions produce ~ ~.
the following results: : ~
_ . _ Rf - value FeCl3 reaction , __ _ _ Desoxy-cohumulone 0.55 black Cohumulone 0.42 blue Hydroperoxide of formula III 0.24 violet ..
_ ___ _ _ .
~ ~.... .
The fractions containing the h~droperoxide of formula III are combined, evaporated in vacuo at -20C and the residue is taken up in deutero-acetone. From the NMR spectrum of this solution 160 MH~; -20C;
TMS (tetramethylsilane) as the internal standard], the following data can be produced on tbe chemical shifts in comparison to c~humulone:
:, ~
!' .
' .
.
'-'''. '' ':~ '.. "';' .. ." .'.' '''''' ''''.'' ' "'.~' ".' '" :: '' ~56~
E ~ ~ E' ~ ~ J
G OOH ~ OH A' \ G~ OH~
E
A OO9S - lo 37 ppm, m Al 0.95 - 1. 30 ppm; m B 3.92 ppm, m, I = 6.5 H~ Bl 3 ~ 77 ppm, m C 3.15 ppm, d, I = 7 H7 C' 3.09 ppm, d, I = 7 H7 D 5.18 ppm, t, I = 7 Hz D~ 5.17 ppm, t, I = 7 Hz E 1.45 - 1.85 ppm, m El 1.45 -- 1.85 ppm, m F 2.52 ppm, d, I = 8 Hz F' 2.57 ppm, d, I = 8 Hz G 4 87 ppm, t, I = 8 Hz G' 5.04 ppm, t, I = 8 Hz Hydroperoxide III
m/e: 364 (3%); 296 (49%), 253 (31%); 181 (28%); 71 (40%); 69 (99%);
67 (18%); 59 (15%); 55 (16%~; 53 (19%); 43 (89%); 41 (100%).
Cohumulone _ .
m/e: 348 (2%); 280 (11%); 224 (10%); 181 (9%); 69 (100%); 53 (14%);
41 (51%)o ~ .
The solution of the hydroperoxide of formula III prepared accord-ing to Example à5 is evaporated at -20 C under a high vacuum. The residue is taken up in 10 ml of benzene. 1 ml portions of this solution are shaken 0 respectively with the following reagents:
a3 dimethylsulphide, 0~5 ml;
.
-359~
b) trimethylphosphite, O.S ml;
c) 0.2 g of sodium iodide + 0~5 ml of acetic acid + 3 ml of water.
By thin-layer chromatography of the benzene solutions, it can be shown that in each case the hydroperoxide of formula III is reduced prac-tically quantitatively to cohumulone. In the case of c), the formation of elementary iodine can also be determined.
Example 3 The procedure described in Example 1 is repeated using desoxy-humulone (compound II with R = isobu-tyl) as the starting material. The o resulting hydroperoxide of formula III (R = isobutyl) shows a violet FeC13 reaction and gives the following mass spectroscopic data:
m/e: 378 (M ), 310, 253, 85, 69, 57.
By reduction of this hydroperoxide (R = isobutyl) with dimethyl-sulphide in benzene there is obtained humulone of formula I (R = isobutyl~.
Example 4 The procedure described in Example 1 is repeated using desoxy-methyl-humulone (compound II with R = methyl). The hydroperoxide of formula III (R = methyl) is purified by preparative column chromatography as described earlier and subjected to mass spectroscopic examination, the following values being obtained:
m/e: 336 (~ ), 268, 253, 69, 43.
The hydroperoxides of formula III may also be prepared and reacted immediately in situ to provide a compound of formula I, without being isolated. ~ typical procedure for this process is given in the following ExampleO
EXample 5 :
6.64 g of desoxy-cohumulone (compound II with R = isopropyl), 5.6 g of potassium t-butylate, 3.65 g of triethylphosphite, 30 ml of N,N-dimethylformamide and 20 ml of t-butanol are added under a nitrogen ~L~5g~3~
atmosphere to a sulphonation flask which is provided with a stirrer, gas delivery tube and thermometer. The mixture is eooled to -30C and oxygen is led in instead of nitrogen. After stirring for 3 hours~ desoxy-cohumulone is no longer present according to thin-layer ehromatographic analysis.
Nitrogen is now again led in in plaee of oxygen and there are carefully added to the mixture 100 ml of 2-N hydrochloric aeid. The mixture is extraeted three times with 500 ml of diethyl ether. The eombined diethyl ether extracts are washed four times with 250 ml of ice-water eaeh time~
dried over sodium sulphate and concentrated under reduced pressure at 30C.
There are obtained 8.92 g of crude product whieh, aeeording to chromatograph-ie analysis, eontains 6.4 g of eohumulone~ The by~produets eonsist almost exelusively of triethylphosphate whieh ean be separated by distillation at 75C/0.01 mm Hg.
~ he present invention is concerned with a process for the manu-facture of humulones.
In our copending application 234~837 is described a process for the preparation of compounds of the general formula I
R (I) / ~ ~ H ::
wherein R represents a Cl 6 alkyl group. .::
According to that process the COlllpOUndS of formula I hereinbefore . ;~
are manufactured by oxidising a compound of the general formula ~ R (II) ::
: HO I OH ::. -where~n R has the signi~icance gi~en earlier~ to give a hydroperoxide of the general form~a ..
-- 1 -- .-.. ....
~iS6~354~
l ll R (III) O OH
.
wherein R has the significance given earlier, and subsequently reducing a hydroperoxide of formula III to give a compound of formula I. :~
The compounds of formula I are intermediates for the manufacture of known bitter substances of the general formula ~o T~ (IV) ~ OH
; wherein R has the significance given earlier3 into which they can be converted by isomerisation in a known manner.
The compounds of formula N are of si~nificance in the beverage industry; for example, in the brewing of beer. Thus, for example, in the brewing of beer, the humulone present in the hops tcompound I with R = iso-~butyl) is converted into isohumulone (compound IV with R = isobutyl) during the boiling of the wort with the hops, by which means the pleasantly bitter flavour is imparted to the beer.
' .
: - 2 -~56~3S4 The process described in application 234,837 enables the com-pounds of formula I and, thus9 also the compounds of formula IV, to be manu-factured in good yields~ which hitherto has not been possible (Riedl, Chem.
Berich~e 85, 692-710, 1952).
Apart from the aforementioned isobutyl group~ exa~lples of Cl 6 alkyl groups are: methyl, isopropyl (compound I = cohumulone)~ sec-butyl (compound I = adhumulone), ethyl (compound I = posthumulone), isoamul (com, pound I = prehumulone).
me hydroperoxides of formula III are novel and constitute the present invention.
mus this invention provides in a first aspect a hydroperoxide of formula III
/ ~ OH o l ll R (III) ,~` \ < ;` OH
'. ~ , wherein R represents a Cl to C6 alkyl group.
In a second aspect this invention provides a process for the preparation of a compound of formula III as defined above which comprises oxidising a compound of formula II
HO ~ OH
, 1 .
_ 3 : . , ; ,.... . . .. . . ... ........ ..
~05~5~
by means of elemental oxygen at a temperature of from about 0C to about -50C in the presence of a base and of a polar aprotic solvent.
The process in accordance with the present invention (i.e. the conversion of a compound of formula II into a compound of formula I) is ex-pediently carried out in the presence of a base and a polar aprotic solvent, preferably at a low temperature and especially at a temperature between 0C
and -50C.
As bases there are preferably used very strong bases such as alkali metal alcoholates derived from lower tertiary alkanols (e.g. potassium t-butylate). However, alkali metal hydroxides (e.g. sodium hydroxide or potassium hydroxide) can also be used. The base is preferably used in excess;
for example, in at least a 2-fold excess.
Ihe nature of the polar aprotic solvent is not critical and, in practice, the choice is only limited by the fact that the solidification point thereof must lie below the relatively low temperature at which the process is carried. out. Examples of suitable polar aprotic solvents are ethers (e~g. tetrahydrofuran), di(lower alkoxy)-(lower alkanes) ~e.g. di-methoxyethane)9 amines such as di(lower alkyl)amines (e.g. dimethylamine), nitriles (e.g. acetonitrile), amides such as N,N-di(lower alkyl)amides de-rived from lower aliphatic carboxylic acids (e.g. N,N-dimethylformamide and N,N-dimethylacetamide) phosphoric acid derivatives (e.g. hexamlethylphosphoric acid triamide) etc.
Better yields are obtained by carrying out the process in an anhydrous medium, but the presence of a slight amount (i.e. a small percent-age) of water does not substantially ~mpalr the yields.
The following Examples illustrate the present invention.
ample Preparation and characterisation of the hydroperoxide of formula III (R = i-C ~7):
3 g of desoxy-cohum~lone are dissolved in 700 ml of hexane, ~56~5~
treated with l g of 10% palladium on active carbon (activated by hydrogen treatment) and oxidised at -20 C for 8 hours with air-oxygen. The mixture is filtered, the filtrate concentrated to ca 50 ml under a high vacuum (0.03 mm Hg) and at a maximum temperature of -20C. This solution is chrom-atographed at -18C on silica gel [pre-washed with methanol/concentrated :~:
hydrochloric acid (9:l)] with pentane/ether ~l:l). There is first eluted desoxy-cohumulone, ~hen cohumulone and finally the hydroperoxide of formula III. From the thin-layer chromatogram [silica gel on glass, washed with methanol/concentrated hydrochloric acid (9:l); eluant: hexane/ether (l:l) + 1% (V/V) glacial acetic acid}, the individual fractions produce ~ ~.
the following results: : ~
_ . _ Rf - value FeCl3 reaction , __ _ _ Desoxy-cohumulone 0.55 black Cohumulone 0.42 blue Hydroperoxide of formula III 0.24 violet ..
_ ___ _ _ .
~ ~.... .
The fractions containing the h~droperoxide of formula III are combined, evaporated in vacuo at -20C and the residue is taken up in deutero-acetone. From the NMR spectrum of this solution 160 MH~; -20C;
TMS (tetramethylsilane) as the internal standard], the following data can be produced on tbe chemical shifts in comparison to c~humulone:
:, ~
!' .
' .
.
'-'''. '' ':~ '.. "';' .. ." .'.' '''''' ''''.'' ' "'.~' ".' '" :: '' ~56~
E ~ ~ E' ~ ~ J
G OOH ~ OH A' \ G~ OH~
E
A OO9S - lo 37 ppm, m Al 0.95 - 1. 30 ppm; m B 3.92 ppm, m, I = 6.5 H~ Bl 3 ~ 77 ppm, m C 3.15 ppm, d, I = 7 H7 C' 3.09 ppm, d, I = 7 H7 D 5.18 ppm, t, I = 7 Hz D~ 5.17 ppm, t, I = 7 Hz E 1.45 - 1.85 ppm, m El 1.45 -- 1.85 ppm, m F 2.52 ppm, d, I = 8 Hz F' 2.57 ppm, d, I = 8 Hz G 4 87 ppm, t, I = 8 Hz G' 5.04 ppm, t, I = 8 Hz Hydroperoxide III
m/e: 364 (3%); 296 (49%), 253 (31%); 181 (28%); 71 (40%); 69 (99%);
67 (18%); 59 (15%); 55 (16%~; 53 (19%); 43 (89%); 41 (100%).
Cohumulone _ .
m/e: 348 (2%); 280 (11%); 224 (10%); 181 (9%); 69 (100%); 53 (14%);
41 (51%)o ~ .
The solution of the hydroperoxide of formula III prepared accord-ing to Example à5 is evaporated at -20 C under a high vacuum. The residue is taken up in 10 ml of benzene. 1 ml portions of this solution are shaken 0 respectively with the following reagents:
a3 dimethylsulphide, 0~5 ml;
.
-359~
b) trimethylphosphite, O.S ml;
c) 0.2 g of sodium iodide + 0~5 ml of acetic acid + 3 ml of water.
By thin-layer chromatography of the benzene solutions, it can be shown that in each case the hydroperoxide of formula III is reduced prac-tically quantitatively to cohumulone. In the case of c), the formation of elementary iodine can also be determined.
Example 3 The procedure described in Example 1 is repeated using desoxy-humulone (compound II with R = isobu-tyl) as the starting material. The o resulting hydroperoxide of formula III (R = isobutyl) shows a violet FeC13 reaction and gives the following mass spectroscopic data:
m/e: 378 (M ), 310, 253, 85, 69, 57.
By reduction of this hydroperoxide (R = isobutyl) with dimethyl-sulphide in benzene there is obtained humulone of formula I (R = isobutyl~.
Example 4 The procedure described in Example 1 is repeated using desoxy-methyl-humulone (compound II with R = methyl). The hydroperoxide of formula III (R = methyl) is purified by preparative column chromatography as described earlier and subjected to mass spectroscopic examination, the following values being obtained:
m/e: 336 (~ ), 268, 253, 69, 43.
The hydroperoxides of formula III may also be prepared and reacted immediately in situ to provide a compound of formula I, without being isolated. ~ typical procedure for this process is given in the following ExampleO
EXample 5 :
6.64 g of desoxy-cohumulone (compound II with R = isopropyl), 5.6 g of potassium t-butylate, 3.65 g of triethylphosphite, 30 ml of N,N-dimethylformamide and 20 ml of t-butanol are added under a nitrogen ~L~5g~3~
atmosphere to a sulphonation flask which is provided with a stirrer, gas delivery tube and thermometer. The mixture is eooled to -30C and oxygen is led in instead of nitrogen. After stirring for 3 hours~ desoxy-cohumulone is no longer present according to thin-layer ehromatographic analysis.
Nitrogen is now again led in in plaee of oxygen and there are carefully added to the mixture 100 ml of 2-N hydrochloric aeid. The mixture is extraeted three times with 500 ml of diethyl ether. The eombined diethyl ether extracts are washed four times with 250 ml of ice-water eaeh time~
dried over sodium sulphate and concentrated under reduced pressure at 30C.
There are obtained 8.92 g of crude product whieh, aeeording to chromatograph-ie analysis, eontains 6.4 g of eohumulone~ The by~produets eonsist almost exelusively of triethylphosphate whieh ean be separated by distillation at 75C/0.01 mm Hg.
Claims (9)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Hydroperoxides of the general formula (III) wherein R represents a C1-6 alkyl group.
2. A compound according to claim 1, wherein R represents the methyl group.
3. A compound according to claim 1, wherein R represents the isopropyl group.
4. A compound according to claim 1, wherein R represents the isobutyl group.
5. A process for the preparation of a compound of formula (III) (III) which comprises oxidising a compound of formula (II) (II) by means of elemental oxygen at a temperature of from about 0°C to about -50°C in the presence of a base and of a polar aprotic solvent.
6. Process according to claim 5 wherein an alkali metal hydroxide or an alkali metal tertiary lower alkanolate is used as the base.
7. Process according to claim 5 wherein R represents the methyl group.
8. Process according to claim 5 wherein R represents the isopropyl group.
9. Process according to claim 5 wherein R represents the isobutyl group.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA305,787A CA1056854A (en) | 1974-09-09 | 1978-06-19 | Hydroxyperoxides |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CH1215674A CH593220A5 (en) | 1974-09-09 | 1974-09-09 | |
| CA234,837A CA1052821A (en) | 1974-09-09 | 1975-09-05 | Process for the manufacture of humolones |
| CA305,787A CA1056854A (en) | 1974-09-09 | 1978-06-19 | Hydroxyperoxides |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1056854A true CA1056854A (en) | 1979-06-19 |
Family
ID=27164097
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA305,787A Expired CA1056854A (en) | 1974-09-09 | 1978-06-19 | Hydroxyperoxides |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1056854A (en) |
-
1978
- 1978-06-19 CA CA305,787A patent/CA1056854A/en not_active Expired
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