Organotin compounds: X. Organotin hydride addition to methyl cyclohexene-1-carboxylate and methyl indene-3-carboxylate

Abstract

Free radical hydrostannation of methyl cyclohexene-1-carboxylate (I) and methyl indene-3-carboxylate (III) with trialkyltin hydrides, R 3SnH (R  Me, n-Bu, Ph) gives the energetically unfavourable cis products, 2-trialkylstannyl cyclohexanecarboxylate (II) and 2-trialkylstannyl indane-1-carboxylate (IV) in high yields, via a trans addition of the tin hydrides. The hydride abstractions by the intermediate trialkylstannylcyclohexanyl (VIII) and trialkylstannylindanyl (IX) intermediate radicals take place stereospecifically, and exclusively from the less hindered ring side. The structures of the isomers II and IV were established by (a) their transformation into the corresponding chlorodialkylstannyl derivatives V and VI, which were shown spectroscopically to have cis stereochemistries by intramolecular complexation of the ester group, and (b) their NMR data. Full 1H, 13C, and 119Sn NMR data are given.