Allenes in Diels–Alder Cycloadditions

Abstract

Abstract For a long time, allenes—and cumulenic systems in general—played a relatively minor role in Diels–Alder cycloadditions. This situation has changed, since allenes are more readily available and as their unique stereochemical features in [4+2]cycloadditions are more widely recognized. This review presents a comprehensive overview of allenes in Diels–Alder processes using selected examples. Allenes in dienes, dienophiles and cycloadducts are covered, inter- and intramolecular Diels–Alder cycloadditions are discussed, and stereochemical features of the addition process are described. Areas of emerging importance are also covered, including allenic components in dehydro-Diels–Alder processes, and dendralenic allenes in Diels–Alder sequences for the rapid generation of target-relevant molecular complexity. Preparatively useful methods for allenic precursor synthesis are also discussed. 1 Introduction 2 Allenic Dienes 2.1 Vinylallenes 2.2 Bisallenes 2.3 Cross-conjugated Allenes 3 Allenic Dienophiles 4 Intramolecular Diels–Alder Cycloadditions 5 Allenic Cycloadducts 6 Conclusions and Outlook

Topics & Concepts