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 cy clization allows the construction of cyclopentyl derivatives 2 bearing four controlled stereogenic centers from diisopropyl precursors 1. Olefins 3 we re also isolated as minor side products. The effect of the acetylenic subst ituent Y has been investigated, and the scope and the limitations of the ca scade have been delineated.