REACTION OF THE LITHIUM DERIVATIVE OF DIETHYL 2-(OR 3-)METHYLPHENYLMETHANEPHOSPHONATE WITH KETONES. AN EXAMPLE OF HIGH SYN-STEREOSELECTIVITY

Abstract

The reaction of the lithium derivative of diethyl ester of 2-(or 3-)methylphenylmethanephosphonic acid (1-Li) with a large number of symmetric and unsymmetric ketones 2a-r is studied at −70°C in THF, the corresponding adducts—diethyl esters of 1-(2- or 3-methylphenyl)-2,2-dialkyl(phenyl)-2-hydroxy-ethanephosphonic acid 3a-r being isolated. The results of stereospecific olefination of the β-hydroxyphosphonates 3j, 3k, 3o and 3p indicate the influence of combined steric effects in ketones 2 and ortho- and metha-methyl substituted benzylphosphonates 1. Spectral investigations and PM3-calculations prove high synstereoselectivity of the reaction of ortho-methyl substituted benzylphosphonates 1a with studied ketones.

Key Words:

• Stereoselectivity
• arylmethanephosphonate carbanion
• reaction with ketones
• 2-hydroxyethanephosphonates
• atropisomers
• PM3-calculations