(E)-1-Bromo-4-trimethylsilyl-1-buten-
3-yne can be as a Nucleophile in the Pd-Catalyzed Cross-Coupling.
Treatment of with t-BuLi (2.1 equiv) in Et2O at ?78°C followed
by addition of dry ZnBr2 (1 equiv) in THF at ?78 to
0°C generates in situ the corresponding alkenylzinc reagent.
Its Pd-catalyzed cross-coupling reaction provides an alternate
and complementary route to conjugated enynes and oligoenynes.
Thus, for example, a difunctional trienyne suitable for the synthesis
of 6,7-dehydrostipiamide (11) has been synthesized from
and (E)-BrCH=C(Me)COOEt in three steps in 75% overall
yield with complete control of regiochemistry and stereochemistry
(Scheme 5).
