The reaction of 5-hexenyl iodides with diethylzinc (2 equiv) and catalytic amounts of a Pd" or Ni" complex like PdCl,(dppf), PdCl,(MeCN),, or Ni(acac), results in an efficient ring closure (THF, RT, 2-12h) affording cyclopentylmethylzinc iodides, which, after transmetalation with CuCN.2 LiCI, can be further functionalized by treatment with a range of electrophiles like allylic halides, acyl chlorides, enones, nitroolefins, ethyl propynoate, and alkynyl halides to yield polyfunctional cyclopentane derivatives. The ring closures occur via radical intermediates, and the stereochemistry of the products can be explained according to the rules for radical cyclizations developed by Beckwith. The preparation of several di-and trisubstitut-