Synthesis and reactivity of 5-Br(I)-indolizines and their parallel cross-coupling reactions

Poorly available 5-iodo- and 5-bromoindolizines were prepared via regioselective lithiation of indolizines followed by halogenation. 5-Halogenoindolizines were found to be passive toward nucleophiles, whereas they may be trifluoroacetylated at C-3 and involved in reaction with DMAD giving cycl[3.2.2]azine. The first successful Suzuki-coupling of 5-bromo(iodo)indolizines with different arylboronic acids (performed as a parallel synthesis) led to a series of 5-arylindolizines; the effect of substituents on the reaction yield was examined.