posted on 2012-09-21, 00:00authored bySanjeewa
K. Rodrigo, Hairong Guan
The development of efficient methods for the synthesis
of molecules with 1,4-difunctionalities has been a dire need of the
synthetic community. In this work, intermolecular reductive coupling
of ynoates and aldehydes (in the presence of a silane) has been accomplished
for the first time using catalytic amounts of Ni(COD)2,
an N-heterocyclic carbene ligand, and PPh3. High regioselectivity
has been demonstrated for the multicomponent coupling reactions, and
more than a dozen invaluable silyl-protected γ-hydroxy-α,β-enoates
have been synthesized. This methodology provides a quick entry to
many other 1,4-difunctional compounds and oxygen-containing five-membered
rings. The intermediacy of metallacycles in the catalytic process
has been established by deuterium-labeling experiments.