Stereoselective Conversion of Stabilized Phosphorus Ylides to Dialkyl 2-(2-Nitro-phenoxy)-2-butenedioates in the Presense of Silica Gel in Solvent-Free Conditions

Abstract

Protonation of the highly reactive 1:1 intermediates, produced in the reaction between triphenylphosphine and dialkyl acetylenedicarboxylates, by 2-nitrophenol leads to vinyltriphenylphosphonium salts, which undergo a Michael addition reaction with a conjugate base to produce dialkyl 2-(2-nitro-phenoxy)-3-(triphenylphosphoranylidene)butanedioates. Silica-gel powder was found to catalyze the stereoselective conversion of dialkyl 2-(2-nitro-phenoxy)-3-(triphenylphosphoranylidene)butanedioates to dialkyl 2-(2-nitro-phenoxy)-2-butenedioates in solvent-free conditions under microwave (0.5 KW, 3 min) and thermal (90°C, 60 min) conditions.

Keywords:

• 2-nitrophenol
• acetylenic esters
• Michael addition
• microwave irradiation
• silica gel
• vinyltriphenylphosphonium salt

Acknowledgments

This work was supported by the Sandoogh Hemayate as Pajuoheshgharane Keshvare Iran via research project number N 84114.