The synthesis of stable 1,3,4-triphenylphospholes

Abstract

The first syntheses of 1,3,4-triphenylphosphole, 2-bromo-1,3,4-phenylphosphole and 2,5-dibromo-1,3,4-triphenylphosphole are described. These phospholes, unlike most of the known derivatives, are difficult to oxidise and they and their corresponding oxides show little tendency to dimerise. The NBS mediated bromination of 1,3,4-triphenyl-2,5-dihydrophosphole oxide led to the desired precursors of the corresponding phospholes and in one case unexpectedly yielded a phosphole oxide directly. Some reactions including the formation of organolithium reagents and their derivatisation are reported. McMurry reactions of derived formylphospholes to give coupled products are described and some copper mediated reactions are also discussed.