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

长期以来，丙二烯和一般的累积系统在 Diels-Alder 环加成反应中的作用相对较小。这种情况已经改变，因为丙二烯更容易获得，并且它们在 [4+2] 环加成中的独特立体化学特征得到了更广泛的认可。本综述使用选定的示例对 Diels-Alder 过程中的丙二烯进行了全面概述。涵盖了二烯、亲二烯体和环加合物中的艾伦烯，讨论了分子间和分子内 Diels-Alder 环加成，并描述了加成过程的立体化学特征。还涵盖了新兴的重要领域，包括脱氢-Diels-Alder 过程中的丙二烯成分，以及 Diels-Alder 序列中的树枝烯丙二烯，用于快速生成与目标相关的分子复杂性。

1 简介

2 艾伦二烯

2.1 乙烯基丙二烯

2.2 双丙烯

2.3 交叉共轭艾伦

3 艾伦亲二烯体

4 分子内 Diels-Alder 环加成

5 Allenic Cyclloadducts

6 结论与展望