An efficient direct phosphinylation and alkylation of ketones to construct C-P and C-C bonds: access to alpha,alpha-disubstituted gamma-ketophosphine oxides

The first example of an acid-promoted difunctionalization of ketones to construct C-P and C-C bonds via a phospha-aldol-elimination is described under metal- and solvent-free conditions. The cascade alpha-phosphorylation and alpha-alkylation sequence directly converts ketones to alpha,alpha-disubstituted gamma-ketone phosphine oxides, thereby providing a new strategy for the synthesis of the alpha,alpha-disubstituted gamma-ketone phosphine oxide anticholinesterase skeleton in moderate to excellent yields with water as the only by-product. Detailed mechanistic experiments verified that the reaction proceeds via a TfOH-induced carbocationic intermediate formed after the alpha-phosphorylation of ketones.