A novel Brønsted acid-catalyzed reaction of alkynyl thioethers with o-hydroxybenzyl alcohols via an unexpected formal [4 + 2] annulation has been developed. This metal-free protocol leads to the facile and practical synthesis of valuable polysubstituted 2H-chromenes in mostly good to excellent yields under mild reaction conditions and features a wide substrate scope and excellent functional group tolerance.Letter pubs.acs.org/OrgLett

A concise and flexible synthesis of α,β-unsaturated amidines via gold-catalyzed intermolecular ynamide amination/carbene 1,2-shift between ynamides and benzylic azides has been developed. Under mild reaction conditions, various α,β-unsaturated amidines were obtained in mostly good yields, thus providing an efficient and atom-economic way for the construction of valuable α,β-unsaturated amidines.

Summary of main observation and conclusion An efficient zinc‐catalyzed oxidative cyclization of readily available indoly ynamides has been developed, enabling rapid and practical access to a diverse array of valuable medium‐sized lactams in mostly good to excellent yields with wide substrate scope. In addition, such an asymmetric synthesis has also been explored by employing the chiral substrate.

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Dearomatization reactions of phenols and their derivatives have evolved as efficient and practical methods for the synthesis of functionalized spirocyclic enones in the past decades. Here, an efficient metal-free intramolecular...