An efficient indole-to-carbazole strategy has been developed under metal-free conditions. This carbazole formation was highly promoted by NHI with high regioselectivity through formal [2 + 2 + 2] annulation of indoles, ketones, and nitroolefins. It thus conveniently enabled the assembly of a large number of diversified carbazole products with good tolerance of a broad range of functional groups.

An efficient one-pot two-step indole-to-carbazole strategy has been developed. This transition metal-free methodology uses oxygen as the sole oxidant and starts from cheap and readily available indoles, ketones, and alkenes. The present protocol efficiently enables the assembly of a diverse array of substituted carbazole products with good regioselectivity and broad tolerance of functional groups.

Thieno[2,3-b]indole derivatives were selectively prepared from indoles, ketones and sulfur powder under metal-free conditions.

A Bronsted acid promoted three-component synthesis of substituted thieno[2,3-b]indole has been developed starting from indoles, alkenes or alkynes, and sulfur powder. N,N-Dimethylformamide plays an important role to convert the starting materials into the fused products. Various functional groups attached to substrates were well tolerated to afford the corresponding products in moderate to good yields under very simple reaction conditions.

An efficient three-component benzoselenophenes formation has been developed from substituted indoles, acetophenones, and selenium powder under metal-free conditions. 2-Aryl indoles played an important role to promote benzoselenophene formation from acetophenone derivatives and selenium powder. One C–C and two C–Se bonds were selectively formed to provide 40 new benzoselenophenes in good yields.