Benzoheterocycles via Metal-Promoted Cyclization of Alkynylarenes

Significance

This methods allows to produce a variety of substituted indoles and benzofurans from available 2-alkynyl-phenols or -anilines. The intermediates are 3-zincated indoles or benzofuranes, which are highly reactive towards various electrophiles. This allows the quick preparation of a large number of heterocycle derivatives. The process is performed in one synthetic step and is operationally simple. The products of the reaction can be used as intermediates for the synthesis of various biologically active products. Besides, it is an interesting example of metallative 5-endo-dig cyclization, promoted by the formation of a zinc alkoxide or amide.