Diastereo- and Enantioselective Synthesis of beta-Amino Cyclic Ethers via the Intramolecular Reaction of gamma-Alkoxyallylstannane with Imine.

Abstract

The intramolecular Lewis acid mediated cyclization of gamma-alkoxyallylstannanes 1, 2, and 14, bearing a hydrazone group at the terminus of the carbon chain, afforded exclusively the corresponding trans beta-amino cyclic ethers 3a, 4a, and 15, respectively. The Lewis acid mediated cyclization of gamma-alkoxyallylstannane 5, having (R)-(+)-1-phenylethylamine as a chiral auxiliary, afforded exclusively trans beta-amino cyclic ether 6a with very high diastereomeric excess (de) in very high chemical yields. The asymmetric cyclization of gamma-alkoxyallylstannane with imine 7 in the presence of chiral titanium-BINOL complex 9, afforded predominantly cis beta-amino cyclic ether 8b with high enantiomeric excess (ee). The chiral Lewis acid mediated cyclization of racemic compound 38 containing phenyl as a substituent afforded cis isomer 39 with very high enantiomeric excess (ee).