Asymmetric Michael addition of formaldehyde N,N-dialkylhydrazones to alkylidene malonates.
Enantiopure formaldehyde N,N-dialkylhydrazones 1 smoothly react with prochiral alkylidene malonates 2 in the presence of MgI2 to afford the corresponding Michael adducts 3 in excellent yields and good diastereoselectivities; direct racemization-free BF3.OEt2-catalyzed thiolysis of the hydrazone C=N bond affords the corresponding dithioketals 7 in optically pure or enantiomerically enriched form.
Departamento de Química Orgánica, Universidad de Sevilla, Apdo de Correos No. 553, 41071 Seville, Spain.
Juan
J
Vázquez
Auxiliadora
A
Prieto
Rosario
R
Fernández
Dieter
D
Enders
José M
JM
Lassaletta