Construction of Heterocycles by the Strategic Use of Alkyne π-Activation in Catalyzed Cascade Reactions

Abstract

This review highlights the synthesis of heterocycles via cascadereactions that involve the activation of an alkyne using carbophilicLewis acids. Primarily guided by the type of reactivity evolvingfrom the alkyne activation, such key steps are categorized as theaddition of simple heteroatom nucleophiles, intramolecular carboalkoxylations,addition of carbonyl nucleophiles, rearrangement of propargylicesters, and enyne cycloisomerizations. Additionally, the functionalizationof existing heterocycles is discussed. 1 Introduction 2 Functionalization of Existing Heterocycles 3 Synthesis of Heterocycles through Cyclization Reactions 3.1 Intramolecular Addition of Simple Heteroatom Nucleophiles 3.2 Intramolecular Carboalkoxylations and Carboaminations 3.3 Carbonyls and Imines as Nucleophiles 3.4 Propargylic Esters 3.5 Enyne Cycloisomerizations 4 Miscellaneous Reactions 5 Conclusions