Palladium-catalyzed cross-coupling of terminal alkynes with 4-trifloyloxazole: studies toward the construction of the C26-C31 subunit of phorboxazole A.

[reaction: see text] A strategy has been developed that successfully takes advantage of transition-metal-catalyzed coupling reactions for the synthesis of highly functionalized oxazoles. Trifloyloxazoles have been used as coupling partners with alkyne-derived vinylmetallic intermediates in Stille- and Negishi-type couplings to assemble the corresponding oxazoles in good isolated yield. The results obtained provide a close analogy and thus good precedent to employ this strategy in the synthesis of the oxazole subunits of phorboxazole A.