IntraMolecular Diels–Alder Reactions of Vinylarenes and Alkynyl Arenes (the IMDAV Reaction)

Abstract

AbstractThis comprehensive review summarizes the published literature data concerning the intramolecular Diels–Alder reactions of vinylarenes (the IMDAV reaction) and alkynyl arenes from 1970 to 2019, and covers mainly intramolecular [4+2] cycloaddition reactions of vinyl- or acetylene-substituted furans, thiophenes, pyrroles, indoles, imidazoles, benzenes, and naphthalenes, in which the unsaturated substituent is linked directly to an arene moiety. The selected area of the Diels–Alder reaction differs from other forms of [4+2] cycloadditions due to the uniqueness of the diene fragment, which, along with an exocyclic multiple bond, includes the double bond of an aromatic or heteroaromatic nucleus in its system. Thus, during the formation of the [4+2] cycloaddition intermediate, the aromaticity of furan, thiophene and even benzene rings is broken, leading, as a rule, to the formation of heterocyclic structures rarely accessible by other methods, in contrast to the majority of intermolecular Diels–Alder reactions, with the highest degree of chemo-, regio-, and diastereoselectivity. Therefore, the IMDAV approach is often used for the synthesis of naturally occurring and bioactive molecules, which are also discussed in this review alongside other applications of this reaction. Whenever possible, we have tried to avoid examples of radical, photochemical, oxidative, precious-metal-complex-catalyzed cyclizations and other types of formal [4+2] cycloadditions, focusing on thermal Diels–Alder reactions in the first step, according to the classical mechanism. The second stage of the process, aromatization, is unique for many initial substrates, and hence considerable attention in this overview is given to the detailed description of the reaction mechanisms.1 Introduction2 IMDAV Reactions of Vinylfurans2.1 Alkenes as Internal Dienophiles2.2 Alkynes and Allenes as Internal Dienophiles3 IMDAV Reactions of Vinylthiophenes3.1 Alkenes as Internal Dienophiles3.2 Alkynes as Internal Dienophiles4 IMDAV Reactions of Vinylbenzothiophenes5 IMDAV Reactions of Vinylpyrroles6 IMDAV Reactions of Vinylindoles6.1 Alkenes as Internal Dienophiles6.2 Alkynes as Internal Dienophiles7 IMDAV Reactions of Styrenes and Vinylnaphthalenes7.1 Alkenes as Internal Dienophiles7.2 Alkynes as Internal Dienophiles7.3 Alkynes as Internal Dienophiles in Aryl Acetylenes (the Intramolecular Dehydro Diels–Alder Reaction)8 IMDAV Reactions of Vinylimidazoles, Vinylisoxazoles and Vinylpyridines9 Conclusion10 Abbreviations