Tandem Mukaiyama Michael–aldol reactions catalysed by samarium diiodide

Samarium diiodide is an efficient precatalyst for tandem Michael–aldol reactions, which allow the formation of two carbon–carbon bonds by successive additions of a ketene silyl acetal and an aldehyde on cyclic α,β-unsaturated 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 PGF2α has been performed by a tandem Michael–aldol samarium-catalysed sequence.