Michael addition of chiral formaldehyde N,N-dialkylhydrazones to activated cyclic alkenes

The nucleophilic conjugate addition of chiral formaldehyde N,N-dialkylhydrazones 1 to doubly activated cyclic alkenes 2-8 proceeds smoothly to afford the corresponding Michael adducts 14, 16, 18, 20, 22, 24, and 25 in variable yields and selectivities. The reactions take place either spontaneously or in the presence of Mgl(2) as a mild Lewis acid depending on the type of substrate. Release of the chiral auxiliary was achieved by transformation of the hydrazone moiety into acetals, dithioacetals or nitriles. (c) 2005 Elsevier Ltd. All rights reserved.