Diastereoselective Synthesis of Housanes via the Carbocupration of Cyclopropenes

Strained bicyclic frameworks have emerged as valuable isosteric replacements and as synthetic platforms based on strain-driven reactivity. The bicyclo[2.1.0]pentane, « housane », a highly strained, nonsymmetrical scaffold constituted of two fused cyclopropane and cyclobutane rings, has long posed a formidable synthetic challenge, with limited accessible substitution patterns. In the past five years, a surge of interest has led to advances in synthetic methodology, paving the way for applications. Here, we report a diastereoselective carbocupration-cyclization cascade of homocarbonyl cyclopropenes that enables efficient access to bicyclo[2.1.0]pentanes while significantly expanding their structural diversity. By exploiting carbonyl groups as productive dual-purpose directing groups and electrophilic partners in cyclopropene carbometallation, this strategy displays high atom-economy and step efficiency. Realization of this approach required overcoming long-standing limitations associated with metallacycle size and carbonyl class in carbometallation reactions. The required cyclopropene starting materials are readily accessed in only two steps from broadly available diazo compounds, alkynes and silyl enol ethers, facilitating the synthesis of structurally diverse compound libraries. The resulting bicyclic scaffold displays exit vectors closely matching those of 1,3-cyclopentanes, and engages in controlled, strain-driven nucleophilic ring-opening transformations, supporting their potential as isosteres or covalent binders. The alcohol handle formed in the cascade enables straightforward diversification of the products, including the first highyielding synthesis and isolation of a bicyclo[2.1.0]pentanone, « housone ». Posted on 21 January 2026-CC-BY 4.0-This is a preprint and has not been peer reviewed. Data may be preliminary.