Rhodium (I) catalysts promote the transformation of o-alkynyl phenols and anilines to the corresponding benzo [b] furans and indoles. The reaction is postulated to proceed via a transient 3-rhodium heterocycle intermediate, which can be trapped with suitable electrophiles to give poly-substituted heterocycles. In the case of mono-substituted electron- withdrawn electrophiles, excellent yield and selectivity for conjugate addition versus Heck ...