Patent GB-790612-A (GB)
Title: Novel unsaturated aldehydes and a process for the manufacture thereof
Filed: 1955-08-16
Abstract: The invention comprises aldehydes having the general formula: <FORM:0790612/IV (b)/1> in which R stands for (2,6,6-trimethyl-cyclohexylidene) - methyl or [2,6,6 - trimethyl-cyclohexen - (2) - ylidene] - methyl or [2,6,6-trimethyl - cyclohexadien - (1,3) - yl] - methyl.  Such compounds are prepared by a process comprising acetylizing iso- or retrodehydro- or b -dehydro-C14-aldehyde in a known manner, condensing the resulting iso- or retrodehydro or b -dehydro-C14-acetal with a vinyl alkyl ether in the presence of an acidic condensing agent and treating the isoretrodehydro or b -dehydro-C16-ether-acetal so obtained with an aqueous acidic agent.  The iso-, retrodehydro- and b -dehydro-C14 aldehydes employed as starting materials are respectively compounds of the general formula: <FORM:0790612/IV (b)/2> wherein R stands for (2,6,6-trimethyl-cyclohexylidene) - methyl, [2,6,6 - trimethyl-cyclohexen - (2) - ylidene] - methyl and [2,6,6 - trimethyl - cyclohexadiene - (1,3) - yl] - methyl.  The iso-, retrodehydro and b -dehydro-C14-acetals are compounds of the formula: <FORM:0790612/IV (b)/3> wherein R has the above meaning and R1 is the characterizing group of the ester radical of the acetylizing agent.  The iso-, retrodehydro- and b -dehydro-C16-ether acetals are compounds of the formula: <FORM:0790612/IV (b)/4> wherein R and R1 have the above meanings and O-R11 is an ether group derived from the vinyl alkyl ether used.  The acetalization in the first step may be carried out by means of an ester of an orthocarboxylic acid, e.g. a triester of an aliphatic orthocarboxylic acid with an aliphatic alcohol, e.g. methyl, ethyl or butyl orthoformate, in the presence of an acid condensation agent, e.g. boron trifluoride etherate, zinc chloride, ammonium nitrate, phosphoric acid or p-toluene-sulphonic acid.  In the second step vinyl methyl, ethyl or butyl ether may be employed in the presence of boron trifluoride etherate, zinc chloride, titanium tetrachloride, aluminium trichloride, ferric chloride or tin tetrachloride.  The third step is carried out in the present e.g. of aqueous p-toluene-sulphonic, acetic, propionic, oxalic, sulphuric or phosphoric acid or water-soluble salts having an acid reaction, e.g. zinc chloride or sodium bisulphate. Preferably oxygen is excluded and an antioxidant, e.g. hydroquinone, is added.  Water is preferably removed continuously during the hydrolysis and a water-miscible solvent, e.g. dioxane, tetrahydrofuran, ethylene glycol or dimethyl ether may be added to the hydrolysis mixture.  Examples are furnished.  The iso-C14-aldehyde is obtained by condensing 2,6,6 - trimethyl - cyclohexanone - (1) with ethoxy - acetylene, treating the product with acid, acetalizing the resulting [2,6,6-trimethyl-cyclohexyl - idene] - acetaldehyde, condensing the resulting acetal with a propenyl ether and treating the condensation product with an acid in accordance with the process of Specification 789,693 or by condensing 2,6,6-trimethyl-cyclohexanone-(1) with 1-methoxy-2-methyl-2-hydroxy-butine-(3), partially hydrogenating the resulting acetylenic glycol, dehydrating the ethylenic glycol so obtained and treating the dehydration product with an acid. The retrodehydro-C14-aldehyde is obtained by partially hydrogenating the ethoxy-(acetylenic carbinol) obtained by condensing [2,6,6-trimethyl-cyclohexen-(2)-one-(1)] with ethoxy acetylene, treating the product with acid, acetylizing the resulting [2,6,6-trimethyl-cyclohexen-(2)-ylidene]-acetaldehyde, condensing the resulting acetal with propenyl ether and treating the product with an acid in accordance with the process of Specification 789,693 or alternatively by condensing b -ionone in a glycide-ester reaction with ethyl chloro-acetate, saponifying the resulting glycide ester with alkali, brominating, the 4 - [21,61,61 - trimethyl - cyclohexen - (11)-yl] - 2 - methyl - buten - (2) - al - (1) with N-bromosuccinimide and splitting off hydrogen bromide from the bromination product by mears of quinoline in accordance with the process of Specification 790,611.  The b -dehydro-C14-aldehyde is obtained by condensing the retrodehydro - C14 - aldehyde with isopropenyl-acetate in the presence of an acidic agent and hydrolysing the resulting 4-[21,61,61-trimethyl - cyclohexadien - (11,31) - yl] - 2-methyl - 1 - acetoxy - butadiene - (1,3) - under mild conditions in accordance with the process of Specification 775,060.