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Large-size macrocycles are synthesizedviathe type-II Alder–ene reaction of arynes generatedviathe hexadehydro Dies–Alder reaction. 

Abstract We describe Pt(II)- and Fe(III)-catalyzed iminocarboxylations of oxime esters conjugated with 1,3-enyne and an ortho-alkynylarene moiety, followed by a spontaneous O→N acyl migration of the enol carboxylate intermediate to generate N-acyl pyrroles and isoindoles. The reaction scope for pyrrole synthesis is general, whereas the formation of isoindoles has a relatively narrow scope because of their instability. 

Abstract We describe novel amine‐mediated transformation of alkynyl ketones and amides to generate 2‐methylene‐2H‐pyrans, substituted 3‐hydroxy‐9H‐fluoren‐9‐ones, and amine‐incorporated arenes. These cascade processes are initiated by conjugate addition of secondary amine followed by hydrolysis of the enamine/vinylogous amide intermediates. The product distribution is highly sensitive to the steric and electronic effects of the substituents on both the alkyne moieties, the tether structure connecting them, and the nature of the amine. Alkynyl amide participates in the Alder‐ene reaction favorably to generate more reactive allene amide that reacts with amine to generate amine‐incorporated arene products. These metal‐free cascade reactions are a useful synthetic method that can be exploited for the construction of various hetero‐ and carbocyclic systems. 

Substituent-dependent reactivity and selectivity in the intramolecular reactions of arynes tethered with an allene are described. With a 1,3-disubstituted allene moiety, an Alder–ene reaction of an allenic C–H bond is preferred over a [2 + 2] cycloaddition, whereas a [2 + 2] cycloaddition of the terminal π-bond of the allene is preferred with a 1,1-disubstituted allene. With a 1,1,3-trisubstituted allene-tethered aryne, an Alder–ene reaction with an allylic C–H bond is preferred over a [2 + 2] cycloaddition. 

Multicomponent reactions (MCRs) constitute a powerful synthetic tool to generate a large number of small molecules with high atom economy, which thus can efficiently expand the chemical space with molecular diversity and complexity. Aryne-based MCRs offer versatile possibilities to construct functionalized arenes and benzo-fused heterocycles. Because of their electrophilic nature, arynes couple with a broad range of nucleophiles. Thus, a variety of aryne-based MCRs have been developed, the representative of which are summarized in this account. 1 Introduction 2 Aryne-Based Multicomponent Reactions 2.1 Trapping with Isocyanides 2.2 Trapping with Imines 2.3 Trapping with Amines 2.4 Insertion into π-Bonds 2.5 Trapping with Ethers and Thioethers 2.6 Trapping with Carbanions 2.7 Transition-Metal-Catalyzed Approaches 3 Strategies Based on Hexadehydro Diels–Alder Reaction 3.1 Dihalogenation 3.2 Halohydroxylation and Haloacylation 3.3 Amides and Imides 3.4 Quinazolines 3.5 Benzocyclobutene-1,2-diimines and 3H-Indole-3-imines 3.6 Other MCRs of Arynes and Isocyanides 4 Conclusion