Patent GB-890758-A (GB)
Title: Novel organo-phosphorus compounds and the manufacture of carotenoid compounds therefrom
IPC: C07F9/54
Filed: 1959-10-23
Abstract: The invention comprises di(phosphonium halides) of the general formula <FORM:0890758/IV (b)/1> wherein Z is an ethenylene or ethynylene group, X is a halogen atom, e.g. Cl or Br, and each R is an aryl radical which may be substituted, e.g. phenyl, paratolyl, p-methoxy-phenyl and naphthyl, The products may be converted to carotenoid compounds by dehydrohalogenation to form the disphosphinylidene compounds and condensing the latter with a polyene aldehyde of the general formula Q.CH=O, wherein Q is a polyolefinic hydrocarbon radical. The di(phosphonium halide) may be obtained by converting a C10 diol of the formula CH2=C(CH3)CH(OH)-Z-CH(OH)C(CH3)=CH2 to the corresponding dihalide, e.g. by reaction with a concentrated aqueous hydrohalic acid, and then reacting the dihalide with a triaryl phosphine (R3P), the reaction being preferably carried out in the presence of a condensation catalyst, e.g. iodine.  The di(phosphonium halide)-compound may be dehydrohalogenated by treating it with phenyl lithium, methyl lithium or a Grignard reagent or similar organo-metal compound to form the diophosphinylidene compound of the formula <FORM:0890758/IV (b)/2> which is then reacted without isolation with two molar proportions of the polylene aldehyde Q.CHO to form an intermediate compound which decomposes spontaneously to yield the carotenoid compound of the formula <FORM:0890758/IV (b)/3> When the radical Z in the carotenoid compound is the ethynylene radical the compound can, if desired, be selectively hydrogenated by known methods to convert the ethynylene radical to the ethenylene radical. Selective hydrogenation may suitably be effected by treating with elemental hydrogen in the presence of a selective hydrogenation catalyst, e.g. palladium/lead.  In Examples (1) 1,8-dibromo-2,7-dimethyl-octadien-(2,6)-yne-4 is formed by treating the appropriate diol with 48% HBr at 0 DEG C.-10 DEG C. and is then reacted with triphenyl phosphine in benzene containing a small amount of iodine to form 1,8-di(triphenylphosphonium bromide) - 2, 7 - dimethyl - octa - dien-(2,6)-yne-(4) which is then dehydrohalogenated with phenyl lithium in ether and the phosphinylidene product reacted with 5-[21,61,61 trimethyl-cyclohexen-(11)-yl-(11) ]-3-methyl-pentadien-(2,4)-al-(1) in ether to form dehydro-beta-carotene; (2) the diol used in (1) is first selectively hydrogenated in toluene in the presence of quinoline and a catalyst comprising palladium/lead on calcium carbonate to form 2,7-dimethyloctatrien-(1,4,7)-diol-(3,6) which is then treated as in (1) via the corresponding di-phosphonium compound to form all-trans-beta-carotene; (3) 1, 8 - di (triphenyl - phosphonium bromide) - 2, 7-dimethyl-octatriene-(2,4,6) is dehydrohalogenated as in (1) and the product treated with 9-[21,61,61-trimethyl - cyclohexen - (11) - yl - (11)] - 3, 7 - dimethyl - nonatetraen - (2, 4, 6, 8) - al - (1) [vitamin A-aldehyde to form all-trans decaprenobetacarotene; (4) as in (3) except that the starting material is 1,8-di(triphenyl-phosphonium bromide) - 2, 7 - dimethyl - octadiene - (2, 6) - yne-(4) and the final product is dehydro-decapreno-beta carotene.  Other caretenoid compounds obtainable are beta-carotene, lycopene, and tetrahydro-lycopene having the formula <FORM:0890758/IV (b)/4>