Patent GB-795227-A (GB)
Title: A process for the manufacture of ª‡,ª‰-unsaturated aldehydes
IPC: C11B9/00
Filed: 1956-09-03
Abstract: a ,b -Unsaturated aldehydes are obtained by reacting a 3,3-disubstituted-allyl halide with an alkali metal salt of a nitronic acid, said substituents being hydrocarbon radicals which may contain oxygen and/or may be linked together.  It is convenient to use the sodium or potassium salt of an aliphatic nitronic acid containing from one to three carbon atoms, e.g. methane, ethane, propane-(1)- or propane-(2)-nitronic acid.  The reaction may be effected at - 10 DEG  to 80 DEG  C. in the presence of anhydrous or aqueous diluents such as alcohols, e.g. ethanol, isopropanol, t-butanol or monoethylene- or diethylene-glycol, water-soluble ethers, e.g. diethylene-glycol ethyl butyl ether, dioxane, tetrahydrofurane; or dialkyl amides such as dimethyl formamide; acetals, e.g. methylal; ketones, e.g. acetone; or acrylonitrile.  The salt of the nitronic acid may be prepared by dissolving the nitro compound in a solution of sodium or potassium hydroxide in water, an acetal or an ether, or by adding a solution of an alkali metal alkoxide (e.g. potassium t-butoxide in t-butanol) to the nitro compound.  Particularly suitable substituted allyl halide starting materials have the general formula <FORM:0795227/IV (b)/1> wherein R represents the phenyl radical or an alkyl radical containing 1 to 5 carbon atoms and R1 represents the methyl radical, or R and R1 together represent a pentamethylene radical and X is a halogen atom, or the corresponding compound in which the 6,7-double bond has been hydrogenated.  The products are valuable scents.  Other suitable starting materials are the 2-cyclohexylidene-ethyl halides in which the cyclohexylidene nucleus may contain one or more double bonds and/or carry alkyl, alkoxy, acyloxy, oxo or ketalized oxo groups as substituents.  The products are scents and may also be used as intermediates for Vitamin A, b -carotene and carotenoids.  In examples: (1) 3,7 - dimethyl - octadien - (2,6) - al - (1) is obtained by dissolving 2-nitropropane in a mixture of aqueous potassium hydroxide and t-butanol and rapidly adding a t-butanol solution of 1-bromo-3,7-dimethyl-octadiene-(2,6); (2) the process is repeated using isopropanol as solvent; (3) the process is repeated using sodium hydroxide with dimethyl formamide as solvent; (4) the process is repeated using lithium hydroxide and dimethyl formamide; (5) 3,7 - dimethyl - octadiene - (2,6) - al - (1) is obtained from 1-chloro-3,7-dimethyloctadiene-(2,6); (6) the same product is obtained from 1 - bromo - 3,7 - dimethyl - octadiene - (2,6) using diethylene glycol ethyl butyl ether as solvent; (7) 3,7-dimethyl-nonadiene-(2,6)-al-(1) is obtained from 1 - bromo - 3,7 - dimethylnonadiene-(2,6); (8) 3,7,9-trimethyl-decadiene-(2,6)-al-(1) is obtained from 1-bromo-3,7,9-trimethyl-decadiene-(2,6) by reaction with a solution of potassium hydroxide and 1-nitropropane in aqueous dimethyl formamide; (9) the process is repeated using a solution of potassium hydroxide and 2-nitropropane in aqueous isopropanol; (10) 3,7-dimethyl-octen-(2)-al-(1) is obtained by reacting 1-bromo-3,7-dimethylocten-(2) with a solution of 2-nitropropane and potassium hydroxide in water and acetonitrile; (11) 3,7,11-trimethyl-dodecene-(2)-al-(1) is obtained by reacting 1-bromo-3,7,11 - trimethyl - dodecene - (2) with a solution of potassium hydroxide and 2-nitropropane in aqueous isopropanol; (12) 3,7,11-trimethyldodecatrien-(2,6,10)-al-(1) is obtained from 1-bromo - 3,7,11 - trimethyl - dodecatriene - (2,6,10) with potassium hydroxide, 2-nitropropane and acetone; (13) (2,6,6-trimethylcyclohexylidene)-acetaldehyde is obtained from (2,6,6 - trimethyl - cyclohexylidene) - ethyl bromide with potassium hydroxide and 2-nitropropane in water and dimethyl formamide; (14) (2,2,6,6 - tetramethyl - cyclohexylidene)-acetaldehyde is obtained from 2-(21,21,61,61-tetramethyl - cyclohexylidene) - ethyl bromide; (15) 2 - isopropyl - 5 - methyl - cyclohexylidene)-acetaldehyde is obtained from 2-(21-isopropyl-51 - methyl - cyclohexylidene) - ethyl bromide; (16) (2,6,6 - trimethyl - 4 - acetoxy - cyclohexylidene)-acetaldehyde is obtained from 2-(21,61,61 - trimethyl - 41 - acetoxy - cyclohexylidene)-ethyl bromide. 3,3-Disubstituted allyl halides of the formula <FORM:0795227/IV (b)/2> where R, R1 and X are as defined above may be obtained by halogenation of the corresponding allyl alcohols with a phosphorus trihalide in an inert solvent.  Alternatively, ketones of the formula <FORM:0795227/IV (b)/3> or the corresponding compounds with a single bond in the 5,6-position, may be condensed with an alkali metal acetylide in liquid ammonia, the resulting acetylenic carbinol partially hydrogenated at the triple bond by means of lead-deactivated palladium/calcium carbonate catalyst and the resulting ethylenic carbinol being halogenated with a phosphorus trihalide or with a hydrohalic acid in an inert solvent at a temperature between 0 DEG  and 20 DEG  C.  The ketone starting material may be obtained as described in Specification 785,086. Substituted 2-cyclohexylidene ethyl halides may be prepared from the corresponding cyclohexanones by a similar method to that described above. Example (13) describes the production of 2,6,6-trimethyl-cyclohexylidene ethyl bromide from 2,6,6-trimethyl-cyclohexane.  Example (16) describes the hydrogenation of 2,6,6-trimethylcyclohexanedione-(1,4) in methanol with Raney nickel to give 2,6,6-trimethyl-4-hydroxy-cyclohexanone-(1) which is heated under reflux with acetic anhydride to give the acetoxy compound; the latter is reacted with lithium acetylide to give 2,6,6 - trimethyl - 1 - ethynyl - 4 - acetoxycyclohexanol-(1) which is partially hydrogenated to 2,6,6 - trimethyl - 1 - vinyl - 4 - acetoxycyclohexanol-(1) and the latter is converted to (2,6,6 - trimethyl - 4 - acetoxy - cyclohexylidene)-ethyl bromide by reaction with phosphorus tribromide. 2,6,6-Trimethyl-cyclohexanedione is described in Specification 791,953.