Tandem Mukaiyama Michael-aldol reactions catalysed by samarium diiodide

Samarium diiodide is an efficient precatalyst for tandem Michael-aldol reac tions, which allow the formation of two carbon-carbon bonds by successive a dditions of a ketene silyl acetal and an aldehyde on cyclic alpha,beta -uns aturated ketones. The adducts are isolated as silyl ethers, in good yields, and in some cases with high diastereoselectivities when the reactions are performed at low temperatures. Comparative study of the activities of other lanthanide iodides for the same tandem reactions is presented. A key step for a formal synthesis of PGF(2 alpha) has been performed by a tandem Micha el-aldol samarium-catalysed sequence. (C) 2001 Elsevier Science Ltd. All ri ghts reserved.