Recent Natural Product Total Syntheses Involving Cycloadditions of Allenes

Comprehensive SummaryAllenes, characterized by their cumulated carbon-carbon double bonds, have emerged as indispensable synthons in the construction of complex natural products. Their unique reactivity and stereochemical properties render allenes a powerful tool for the efficient and streamlined total synthesis of structurally intricate natural products. This review comprehensively summarizes the total syntheses of complex natural products involving allene cycloaddition reactions reported over the past decade (2014-2024). Among the nearly 20 total syntheses reviewed, the [2+1], [2+2], [3+2], [4+2], [4+3], [5+1] and [2+2+1] cycloaddition reactions of allenes are the most important transformations to construct the key skeleton. This is because of their ability to form multiple bonds in a single step with high atom economy, stereoselectivity, and regioselectivity, often under mild conditions. The strategic application of these reactions in forming key carbon-carbon bonds and controlling stereochemistry makes them practical for the efficient assembly of complex molecular frameworks. With the ongoing exploration of methods for allene generation, particularly the enantioselective approaches, and the continued discovery of novel cyclization reactions of allenes, allene chemistry will maintain its crucial and indispensable role in the total synthesis of natural products.