Pd-catalyzed cross-coupling reaction of (Z)- and (E)-bromoenyne: unusual stereochemical outcome

Pd-catalyzed cross-coupling reaction of (E)-bromoenyne 1Z with 1-alkyne and tributylvinyl–stannane occurs with retention of the configuration in benzene but with an inversion of the configuration in DMF or CH2Cl2. On the other hand, that of (Z)-bromoenyne 1E occurs with retention of the configuration in these solvents.