One-Pot Tandem Annulation of N -(2-Alkynylaryl)- N -sulfonylcyanamides with Water for the Synthesis of 2-Amino-3-carbonylindoles

A metal-free, one-pot tandem annulation of N-(2-alkynylaryl)-N-sulfonylcyanamides with water has been developed for synthesizing 2-amino-3-carbonylindoles. The reaction proceeds via isolable N,O-BF2-chelated intermediates, which undergo Et3N-mediated ring opening. Water serves as the carbonyl oxygen source, as supported by anhydrous control and H218O-labeling experiments. The protocol tolerates diverse sulfonamide groups and substituents, enables gram-scale synthesis, and allows for subsequent deprotection.