Stereochemical aspects of substitution reactions of stannyl and germyl anionoids with cyclohexyl derivatives

The reactions of trimethyltinlithium (in THF) and trimethylgermaniumlithium (in HMPA) with some 4-alkylcyclohexyl bromides and tosylates have been conducted, and product stereochemistry has been established by and 13C NMR spectroscopy. With the cis bromides both the stannyl and the germyl anionoids yield mixtures of cis-and trans-4-alkylcyclohexylstannanes and -germanes, respectively, whereas the stannyl anionoid reacts cleanly with inversion with trans-4-methylcyclohexyl tosylate. Both anionoids react in a straightforward way with cyclohexene oxide to yield the corresponding trans -2-hydroxycyclohexyl metalloids. Certain of our results contrast with some of those in a previous report. Variable-temperature 13C NMR examination of cis-4-methylcyclohexyltrimethylgermane, and other considerations, yield a - ΔG°[Ge(CH)] of 2.1 ± 0.2 kcal/mol (A value), somewhat greater than the A value for CH (1.74 kcal/mol).