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DOI: 10.1055/s-1995-4841
Preparation of Carbocyclic and Heterocyclic Compounds by the Use of an Allylzinc and an Allylpalladium in Tandem
Publication History
Publication Date:
31 December 2000 (online)
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During the last decade, part of our work was directed at the construction of methylene derivatives of five- and six-membered carbocyclic and heterocyclic compounds (1): methylenecyclopentenes, methylenecyclopentanes, methylenetetrahydrofurans, methylenepyrrolidines and methylenetetrahydropyrans. 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 give 4, which can be derivatized or, more importantly, cyclized to 1 in situ by Pd(0) catalyzed elimination of met-OR2. Special features are the one-pot nature, cleanliness and mildness of most procedures leading to 1. So far, we have found that silyl ether, acetal and ester groups as well as primary C-Cl remain unaffected by zinc reagents 2 (met=ZnBr) under our reaction conditions.1 In initial studies, 3-metallomethyl derivatives of 5-methylenetetrahydropyrans and 5-methylene-N-methylpiperidine were obtained by an intramolecular version of the addition step, a type-II zinc-ene reaction of 2-(bromozincmethyl)-2-propenyl alkenyl ethers and N-methyl-N-{2-(chloromagnesiomethyl)-2-propenyl}allylamine, respectively. An extension of the main theme concerns the preparation of 3,4-dimethylene derivatives of tetrahydropyran and N-methylpiperidine.
Cyclopentenes - cyclopentanes - tetrahydrofurans - pyrrolidines - tetrahydropyrans