Transformations of 3-Zinciobenzofurans and 3-Zincioindoles

Significance

Starting from a simple, Sonoga­shira-derived 2-ynyl phenol or 2-ynyl aniline A, a potentially general approach to functionalized conjugated benzoheteroles (benzofurans and indoles) C via 3-zincio intermediates B is presented. Thus, Negishi cross-coupling of species B with various halides affords products C in excellent yields. Protonation, deuteration, and reaction with iodobenzene lead to the formation of 3-H-, 3-D-, and 3-phenyl-substituted heteroles C (n = 1). The low reactivity of the zinc phenoxide intermediates in the absence of TMEDA is rationalized by their propensity to form coordinatively saturated oxygen-bridged aggregates, in contrast to the corresponding zinc anilides.