Sulfonamide and Tertiary Amine as Nucleophiles in Pd(II)-Catalyzed Diamination of Alkynes: Synthesis of Tetracyclic Indolobenzothiazine S,S‑Dioxides

Pd­(II)-catalyzed oxidative double cyclization of the 1,2-diarylethynes bearing an N-methyl-N-(2-methoxy­carbonyl)­ethyl­amino and an amino­sulfonyl group afforded indolo­benzo­thiazine S,S-dioxides in good to excellent yields. The 2-(methoxy­carbonyl)­ethyl group attached to the indolyl nitrogen is readily removed under basic conditions (DBU, DMF, 120 °C) to provide the corresponding tetracycles with a free indolyl nitrogen in excellent yields.