A Click Reaction Enabled by Phosphorus‐Oxygen Bond for Synthesis of Triazoles

Abstract

Synthesis of various NÀ H triazoles via azidyl radical was achieved using diphenyl phosphoryl azide (DPPA) and internal alkynes containing carbonyl group in wet-DMSO at 90°C in excellent yield. Mechanistic investigations revealed that an azidyl radical was generated in the reaction medium. The driving force was probably due to the presence of the C=O group of ester or ketone in conjugation with the triple bond of the substrate. This resulted in cleavage of the phosphorus nitrogen (PÀ N) bond of DPPA by forming an allenic intermediate. The C=O group of the ester or ketone is a determinant factor that results in triazole as the outcome. The formation of the phosphorus oxygen bond resulted in cleavage of a strong PÀ N bond (617.1 � 20.9 kJ mol À 1 ) of phosphoryl azidate in an additive free Click reaction of internal alkynes. Overall, good to excellent yield of N 1 -H triazole scaffolds were synthesized following the protocol.