5-Endo-Trig Radical Cyclizations of Bromomethyldimethylsilyl Diisopropylpropargylic Ethers. A Highly Diastereoselective Access to Functionalized Cyclopentanes

An efficient radical sequence involving a 5-exo-dig, a diastereoselective 1,5-H transfer, and a rarely observed in an all-carbon system 5-endo-trig cyclization allows the construction of cyclopentyl derivatives 2 bearing four controlled stereogenic centers from diisopropyl precursors 1. Olefins 3 were also isolated as minor side products. The effect of the acetylenic substituent Y has been investigated, and the scope and the limitations of the cascade have been delineated.