THE SYNTHESIS OF ALKENES VIA EPI-PHOSPHONIUM SPECIES - 2 - A PHOSPHORUS RAMBERG-BACKLUND REACTION

Stilbene may be synthesised with Z-selectivity from (alpha-bromobenzyl )benzyldiphenylphosphonium bromide by the action of amine bases. A ser ies of stilbenes was synthesised by the action of N-bromosuccinimide a nd 2,2,6,6-tetramethylpiperidine directly upon dibenzyldiphenylphospbo nium salts. The reaction, essentially a phosphonium analogue of the Ra mberg-Backlund displays cis selectivity. The dibenzyldiphenylphosphoni um salts were prepared by the one pot polymethylhydrosiloxane/titanium (Iv) isopropoxide mediated reduction/alkylation of benzyldiphenylphosp hine oxides. (C) 1998 Elsevier Science Ltd. All rights reserved.