Reversibility of Betaine Formation During the Wittig Reaction

cf. W., et al., CA 55, 13345h. The decompn. of such betaines derived from a nonmesomery-stabilized phosphorylide into their components was demonstrated in 2 ways. The betaine, Ph3+PCHMeCHPhO(I, erythro and threo forms) suspended in C6H6 or dissolved in Me3COH-Et2O treated with p-C1C6H4CHO and shaken 16 h. at 20 Deg yielded 38 and 52% cis- and trans-p-C1C6H4CH:CHMe together with 25 and 18% cis- and trans-PhCH:CHMe (from C6H6 and Me3COH-Et2O solns., resp.). I (90:10 or 99:1 threo-erythro) shaken 30 h. in C6H6 suspension at 20 Deg gave 50% I contg. 95:5 threo-erythro. Under the same conditions after 30 h. I contg. 10:90 threo-erythro had the compn. 75:25 threo-erythro. The diastereomeric relations were detd. by treating I with HBr in Et2O, isolating the mixt. of threo and erythro hydroxyphosphonium salts, (II), [Ph3P+CMeCHOHPh]-Br, and fractionating the salt from CH2Cl2 into the 94% erythro-rich component, m. 185-7 Deg, and the 80% threo-rich oil. Treatment of these fractions gave cis- and trans-MeCH:CHPh. The enriched II were converted with PhLi into the corresponding I. [on SciFinder (R)]

Published in:
Angewandte Chemie, International Edition, 4, 689-690
CAN 63:72150 39 Organometallic and Organometalloidal Compounds Univ. Heidelberg,Germany. Journal written in German. 766-90-5 (Benzene, propenyl-, cis-); 873-66-5 (Benzene, propenyl-, trans-); 1879-52-3 (Benzene, 1-chloro-4-propenyl-, cis-); 3412-46-2 (Phosphonium, (b-hydroxy-a-methylphenethyl)triphenyl-, bromide, erythro-); 3412-47-3 (Phosphonium, (b-hydroxy-a-methylphenethyl)triphenyl-, bromide, threo-); 3412-63-3 (Phosphonium, (b-hydroxy-a-methylphenethyl)triphenyl-, hydroxide, inner salt, erythro-); 3412-64-4 (Phosphonium, (b-hydroxy-a-methylphenethyl)triphenyl-, hydroxide, inner salt, threo-) (prepn. of)

 Record created 2006-03-03, last modified 2018-01-27

Rate this document:

Rate this document:
(Not yet reviewed)