Reactions of carbonyl compounds with tervalent phosphorus reagents. Part 12. Aromatic aldehydes with bromophosphines and phosphorus tri-iodide

Abstract

The reactions of aromatic aldehydes with phosphorus tribromide (4a), with phosphours tri-iodide (3), and with bromodiphenylphosphine (4b) have been investigated in detail. Both the trihalides react as electrophiles to produce high yields of the appropriate benzylidene dihalide. Thereafter, these reactions differ from each other and from that of phosphorus trichloride. Bromodiphenylphosphine (4b) reacts in biphilic fashion to produce (α-bromobenzyl)diphenylphosphine oxide (15). This oxide is readily dehalogenated under the reaction conditions and in model studies. Cyanodiphenylphosphine is unreactive towards benzaldehyde These halogenophosphine reactions confirm the generality of the trends first observed with chlorophosphines and that the nature of the other two ligands on phosphorus determines the mode of reaction with aldehydes.