Palladium-catalyzed cyclization reactions of 2-vinylthiiranes with heterocumulenes. Regioselective and enantioselective formation of thiazolidine, oxathiolane, and dithiolane derivatives
C. Larksarp et al., Palladium-catalyzed cyclization reactions of 2-vinylthiiranes with heterocumulenes. Regioselective and enantioselective formation of thiazolidine, oxathiolane, and dithiolane derivatives, J ORG CHEM, 66(10), 2001, pp. 3502-3506
The first palladium-catalyzed ring-expansion reaction of 2-vinylthiiranes w
ith heterocumulenes to form sulfur-containing five-membered-ring heterocycl
es is described. This regioselective reaction requires 5 mol % of Pd-2(dba)
(3). CHCl3 and 10 mol % of bidendate phosphine ligand (dppp, BINAP), at 50-
80 degreesC, in THF. The reaction of 2-vinylthiiranes with carbodiimides, i
socyanates, and ketenimines affords 1,3-thiazolidine derivatives, whereas t
he reaction with diphenylketene or isothiocyanates results in the formation
of 1,3-oxathiolane or 1,3-dithiolane compounds in good to excellent isolat
ed yields and in up to 78% ee.