Ester Groups as Effective Ligands in Chelate-Controlled Additions of Cuprates and Grignard Reagents to Chiral β-Formyl Esters

Article abstract of DOI:10.1021/jo00075a022

Addition of cuprates to chiral methyl β-formyl carboxylates 1a-1d provided γ-lactones 2-7 in excellent trans-selectivity.The high diastereofacial selectivity was only obtained employing diethyl ether as solvent while tetrahydrofuran gave inferior results.Similar solvent effects were observed in the additions of various Grignard reagents to 1a, which afforded γ-lactones 2, 3, 12, and 13 in moderate trans-selectivity.The best solvent for these reactions was dichloromethane.The 1,3-induction of cuprate additions was studied by using aldehydes 8a-8c.The results obtained were interpreted in terms of chelate-controlled additions with formation of seven-membered ring chelates which involve both carbonyl functions of aldehyde 1 or 8.The function of ester groups as effective ligands of lithium or MgX cations may also be of importance for other stereoselective reactions employing organometallic reagents.