[reaction: see text] Biaryl bromides such as 1 (R=NO(2), H, OMe) undergo the Heck reaction to give both the expected products 3 ("retention") as well as "crossover" products 4 derived from a migration of Pd and net transfer of reactivity from one aryl ring to the other. Under the conditions used, crossover is increasingly favored when electron-deficient arenes are involved. Crossover products derived from transfer onto the pyridine ring have also been observed.

Alkenes Alkenes Q 0083 C-H Activation and Palladium Migration within Biaryls under Heck ReactionConditions. -Biaryl monobromides are observed to furnish in Heck reactions both the expected "retention" products as well as "crossover" products resulting from Pd transfer. Later products are increasingly favored when electron-deficient arenes are involved. -(KARIG, G.; MOON, M.-T.; THASANA, N.; GALLAGHER*, T.; Org. Lett. 4 (2002) 18, 3115-3118; Sch. Chem., Univ. Bristol, Cantock's Close, Bristol BS8 1TS, UK; Eng.) -Nuesgen 03-065 2002 Alkenes