Patent GB-803178-A (GB)
Title: Process for the reduction of organic compounds
IPC: C07D307/44
Filed: 1956-07-11
Abstract: Organic compounds containing multiple bonds between carbon and oxygen and/or carbon and nitrogen are reduced by means of a dialkyl aluminium hydride or an aluminium tri-isoalkyl or a complex compound of one of these compounds with an alkali metal hydride.  In particular aldehydes, ketones, carboxylic acids, their anhydrides, esters or lactones are reduced to alcohols, acid amides or nitriles are reduced to amines, and lactams or oximes to imines.  Preferred aluminium tri-isoalkyls have the general formula [RR1CHCH2-]3Al, in which R and R1 are alkyl groups.  The number of effective reduction equivalents per mol. of aluminium compound depends upon the substance to be reduced, thus 3 reduction equivalents are available when reducing chlorinated, aromatic or unsaturated aldehydes, whereas only 1 equivalent is available for the reduction of acid esters, ketones, and nitriles.  The intermediate aluminium complexes are decomposed by addition of water with the formation of aluminium hydroxide. In examples: (1) benzaldehyde is added dropwise to aluminium tri-isobutyl, when isobutene is evolved, the mixture decomposed with dilute H2SO4 and benzyl alcohol isolated with ether; similarly p-chlorobenzyl alcohol, anisyl alcohol, furfuryl alcohol and 2-hydroxymethyl thiophene are prepared from the corresponding aldehydes and also camphor is reduced to a mixture of borneol and isoborneol, methyl trichloracetate to trichlorethanol, methyl benzoate to benzyl alcohol, methyl caprate to decanol-(1), methyl pyromucate to furfuryl alcohol, methyl nicotinate to pyridine-3-carbinol, and benzonitrile to benzylamine; using aluminium diisobutyl hydride, oestrone is reduced to estradiol, dimethyl brassylate to tridecane-1,13-diol, butyrolactone to butane-1,4-diol, pentadecanolide to pentadecane-1,15-diol, decamethylene dicarboxylic acid dinitrile to 1,12-diamino dodecane, undecylenic acid to undecenol and thence with an additional mol. of reducing agent to undecane-1,11-diol, trifluoracetic acid to fluoral hydrate (below 0 DEG  C.) or trifluoroethanol (20-30 DEG  C.), N-cyclohexyl benzamide to N-cyclohexyl benzylamine, benzoyl methyl anilide to benzaldehyde and then benzyl alcohol, methyl anthranilate to o-aminobenzyl alcohol, a -aminobutyronitrile to 1,2-diaminobutane, benzal aniline to benzyl aniline, and quinoline to dihydroquinoline; cinnamyl, a -amylcinnamyl, furfurylallyl, and hydrocinnamyl alcohols, 2-ethyl hexanol, 2-ethyl butanol, cyclohexanol, civetol, tetrahydro-a -naphthol and cyclodecane-1,6-diol are obtained from the corresponding aldehydes or ketones; trichloracetophenone and aluminium tri-isohexyl yield trichloromethyl-phenyl carbinol; methyl nonyl ketone and aluminium di-isohexyl hydride give methyl nonyl carbinol; likewise benzyl acetone gives methyl phenylethyl carbinol; fluorenone is reduced with aluminium diethyl hydride to fluorenol, benzophenone to benzhydrol, Michler's ketone to p,p1-dimethylaminodiphenyl carbinol, androstene-3:17-dione 3-ethyl enol ether to testosterone, dimethyl terephthalate to 1,2-dimethylolbenzene, dimethyl muconate to hexadiene-2,4-diol-1,6, tetrahydrophthalic anhydride to 1,2-dimethylol-cyclohexene-4, endomethylene tetrahydrophthalic anhydride to D 4-endomethylene-tetrahydrophthaldiol, endoanthracene maleic acid anhydride to 9:10-anthracene diethanol, caprolactam to hexamethylene imine, cyclodecanone iso-oxime to decamethylene imine, and Vitamin A acid methyl ester to Vitamin A alcohol; while using sodium aluminium di-isobutyl dihydride, dimethyl sebacate is reduced to decane-1,10-diol and diethylaminoacetonitrile to N:N-diethyl ethylene diamine.  Specification 774,516 is referred to.