Cyclopropyl building blocks for organic synthesis, 131. Palladium-catalyzed bicyclization with carbonyl insertion of alkenyl-tethered propargyl carbonates towards a scalable synthesis of various 2-(bicyclo[3.1.0]hex-1-yl)acrylates

Article abstract of DOI:10.1002/adsc.200606155

The Pd-catalyzed 5-exo-trig-3-exo-trig cascade cyclization of 1,6-enynes with a propargyl carbonate terminus offers the shortest synthetic route to variously substituted 2-(bicyclo[3.1.0]hex-1-yl)acrylates, a novel class of prospective monomers for low-shrinkage polymers. To apply this reaction to large-scale preparations of the said bicyclic acrylates, a flexible Pd catalyst system with tunable reactivity has been developed. The dependence of the product and diastereomer distribution on both the reaction conditions, including the type of palladium catalyst used, and on the nature of the substrate has been investigated. A variety of methyl 2-(bicyclo[3.1.0]hex-1-yl)acrylates and parent carboxylic acids as well as some of their derivatives of potential interest towards a technical application were prepared on a multigram scale. A general large-scale synthesis of the cyclization precursors bearing one or two carbonyl groups in the tether is also disclosed.