PREPARATION OF CARBOCYCLIC AND HETEROCYCLIC-COMPOUNDS BY THE USE OF AN ALLYLZINC AND AN ALLYLPALLADIUM IN TANDEM

During the last decade, part of our work was directed at the construct ion of methylene derivatives of five- and six-membered carbocyclic and heterocyclic compounds (1): methylenecyclopentenes, methylenecyclopen tanes, methylenetetrahydrofurans, methylenepyrrolidines and methylenet etrahydropyrans. Our routes start with the addition of 2(metallomethyl )-2-alkenyl ethers (2) to C=C, C=X (X=C, O, NR), and epoxides (3) to g ive 4, which can be derivatized or, more importantly, cyclized to 1 in situ by Pd(0) catalyzed elimination of met-OR(2). Special features ar e the one-pot nature, cleanliness and mildness of most procedures lead ing to 1. So far, we have found that silyl ether, acetal and ester gro ups as well as primary C-Cl remain unaffected by zinc reagents 2(met=Z nBr) under our reaction conditions. In initial studies, 3-metallomethy l derivatives of 5-methylenetetrahydropyrans and 5-methylene-N-methylp iperidine were obtained by an intramolecular version of the addition s tep, a type-II zinc-ene reaction of 2-(bromozincmethyl)-2-propenyl alk enyl ethers and N-methyl-N-(2-(chloromagnesiomethyl)-2-propenyl) allyl amine, respectively. An extension of the main theme concerns the prepa ration of 3,4-dimethylene derivatives of tetrahydropyran and N-methylp iperidine.