Allenes in Diels-Alder Cycloadditions

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.

Automated summary

Allenes have traditionally played a minor role in Diels-Alder cycloadditions, but their importance has grown with their increased availability and unique stereochemical features. This review provides a comprehensive overview of allenes in Diels-Alder processes, covering their application in dienes, dienophiles, and cycloadducts, discussing both inter- and intramolecular cycloadditions, and describing the stereochemical aspects of the addition process. Emerging areas such as the use of allenic components in dehydro-Diels-Alder processes and dendralenic allenes for rapid generation of molecular complexity are also addressed, along with preparatively useful methods for allenic precursor synthesis.