METALATION INDUCED REARRANGEMENT OF DI-t-BUTYL(3-SUBSTITUTED PHENYL)PHOSPHATES

Abstract

Treatment of di-t-butyl(3,5-dimethylphenyl)phosphate lb with lithium diisopropylamide at −78°C followed by warming to rt yields di-t-butyl(2-hydroxy-4,6-dimethylphenyl)phosphonate 2b. Di-t-butyl(3-methoxyphenyl)phosphate 1c on similar treatment with LDA yields di-t-butyl(2-hydroxy-6-methoxyphenyl)phosphonate 2c. Similarly di-t-butyl(3,5-dimethyloxyphenyl)phosphate 1d rearranges to di-t-butyl(2-hydroxy-4,6-dimethoxyphenyl)phosphonate 2d. Di-t-butyl(2-di-t-butoxyphosphinyl-3,5-dimethoxyphenyl)phosphate 3, when treated with LDA, yields tetra-t-butyl(2-hydroxy-4,6-dimethoxy-1,3phenylene)bis(phosphonate) 4. The phosphonates 2c and 2d on treatment with trifluoroacetic acid in toluene are converted into the corresponding phosphonic acids 2e and 2f respectively.

Key Words:

• Lithiation
• phosphate-phosphonate rearrangement
• phosphonic acids.