We report a unified, metal-free strategy that employs terminal heteroatom (chalcogen or halogen)-substituted homopropargylic amines as key substrates. Their cyclization with heteroallenes (e.g., CO2, CS2, isocyanates) under mild conditions efficiently affords three classes of six-membered N-heterocycles. The protocol is scalable and the products feature a versatile exocyclic vinyl-heteroatom handle for diversification. Mechanistic studies, supported by DFT calculations, highlight the heteroatom’s essential function in activating the alkyne for the pivotal 6-exo-dig cyclization.
Zhong et al. (Thu,) studied this question.
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