Generation of Sulfonylated Tetrazoles through an Iron-Catalyzed Multicomponent Reaction Involving Sulfur Dioxide

Abstract

Summary As a privileged motif, tetrazoles can be widely found in pharmaceuticals and materials science. Herein, a five-component reaction of cycloketone oxime esters, alkynes, DABCO·(SO 2 ) 2 , and two molecules of trimethylsilyl azide under iron catalysis is developed, giving rise to a range of cyano-containing sulfonylated tetrazoles in moderate to good yields. This multicomponent reaction exhibits excellent selectivity and enables the formation of multiple new chemical bonds in one pot. A possible mechanism involving azidosulfonylation of alkynes, C-C bond cleavage of both cycloketone oxime esters and alkynes, and [3 + 2] cycloaddition of trimethylsilyl azide and the nitrilium cation intermediate is proposed. Additionally, the potential of terminal alkynes acting as powerful synthons for the synthesis of tetrazoles in a radical initiated process is demonstrated for the first time.

Multicomponent Reactions Based on SO2 Surrogates: Recent Advances

“…Finally, the radical IV takes azide group from the Fe(III)N 3 species to give the desired product, concurrent with the regeneration of Fe(II) species. Furthermore, terminal alkynes were proved to be ideal cyanoalkylsulfonyl radical acceptors, furnishing numerous cyano‐containing sulfonylated tetrazoles [43] …”

“…Furthermore, terminal alkynes were proved to be ideal cyanoalkylsulfonyl radical acceptors, furnishing numerous cyano-containing sulfonylated tetrazoles. [43]…”