Metal-Free [5 + 1] Cycloaddition–Aromatization of Benzotriazoles and Sulfur Ylides to Construct 1,2,4-Benzotriazines

Abstract

Reported herein is a novel [5 + 1] cycloaddition− aromatization of benzotriazoles and sulfur ylides to efficiently construct 1,2,4-benzotriazine derivates with good yield. This new protocol does not employ any transition metal reagent and enables the cycloaddition by cleavage of the N−N single bond. The use of inexpensive and readily available starting materials, a broad substrate scope, mild reaction conditions, metal-free, and versatile functionalization of the 1,2,4-benzotriazines make this strategy more attractive.

Ac-l-methionine-catalyzed, nitrite-triggered cycloaddition reactions between bromides and alkynes/alkenes: step-economical reactions for modular synthesis

“…8 More importantly, what makes sulfur ylides unique is their extraordinary stability toward H 2 O and O 2 . However, sulfur ylides consist of a negatively charged carbanion and an adjacent positively charged sulfonium salt; thus, they are generally investigated as highly reactive one-carbon (C1) synthons for [5 + 1], 9 [4 + 1], 10 [3 + 1] 11 and [2 + 1] 12 cycloadditions. In comparison, the cycloaddition between a sulfur ylide and 2π acceptors to afford five-membered skeletons is underdeveloped.…”

Synthesis of α-pyrones via gold-catalyzed cycloisomerization/[2 + 1] cycloaddition/rearrangement of enyne-amides and sulfur ylides

“…6 b Recently, the Deng group developed a relay catalytic strategy using a gold/palladium system for the efficient synthesis of furan-fused seven-membered heterocycles through the cycloisomerization/asymmetric [4 + 3] cycloaddition cascade reaction of enyne-amides with trimethylenemethane (TMM) donors. 6 e Our group has developed a novel catalyst-controlled cycloisomerization/[4 + 3]-cycloaddition sequence of enyne-amides and crotonate-derived sulfur ylides 7 to construct diverse substituted 2,3-furan-fused dihydroazepines and 2,3-pyrrole-fused dihydrooxepines (Scheme 1b). 6 d…”