James W. Hershberger

Evaluation of tributylgermanium hydride as a reagent for the reductive alkylation of active olefins with alkyl halides

Abstract The reductive alkylation of acrylonitrile and of 2-cyclohexen-1-one by alkyl halides using tributylgermanium hydride was systematically evaluated. The performance of the germanium reagent was compared to that of the more commonly employed tributyltin hydride. For certain applications the germanium reagent afforded improved yields without the use of large excess olefin concentrations. Disadvantages of the germanium reagent include a tendency to hydrogermylate active terminal olefins and a general low reactivity towards alkyl halide substrates. The following series of six other triorganotin and triorganogermanium hydrides were also briefly screened for possible application to reductive alkylations: trimesityltin hydride, trimesitylgermanium hydride, triphenyltin hydride, triphenylgermanium hydride, trineopentyltin hydride, and tricyclohexylgermanium hydride.

Alkyl additions to active olefins by tributylgermanium hydride reduction of alkyl halides

Abstract Tri( n -butyl)germanium hydride is a superior reagent for the reductive addition of alkyl halides to active olefins.

Reactivity of allylic and vinylic silanes, germanes, stannanes and plumbanes toward SH2′ or SH2 substitution by carbon- or heteroatom-centered free radicals

Compounds of the type CH2CHCH2MR3 and E-PhCHCHMR3 (M  Si, Ge, Sn, Pb) were allowed to react with a series of heteroatom-centered radicals (PhY ·, Y = S, Se, Te, derived from PhYYPh) and carbon-centered radicals ((CH3)2CH · derived from (CH3)2CHHgCl). We report that alkenylplumbanes and, under forcing conditions, alkenylgermanes undergo SH2 or SH2′ substitution of the metal by chain mechanism analogous to those previously reported for alkenylstannanes. Alkenylsilanes are unreactive. Based solely upon product yields, the following trends were observed: The reactivity of the alkenylmetals follow the order metal = Pb > Sn > Ge (> Si). The allylmetals were more reactive then the β- metallostyrenes toward the reactants employed in this study. The chalcogen series PhYYPh exhibits the reactivity order Y = S > Se > Te.

The effects of counterion and solvent on the reactivity of nickel acylate complexes

Abstract Nickel acylate complexes, which can be generated starting with a carbon, nitrogen or oxygen nucleophile, act as acyl anion equivalents and therefore are an excellent method of assembling complex organic molecules from readily available starting materials. In an effort to increase the synthetic utility of these easily formed reagents, a systematic study of the reactivity of the nickel acylate complex generated under a variety of conditions was performed. Those acylate complexes generated with a carbon based nucleophile, such as a butyl or phenyl anion, show a large change in reactivity upon changing, for example, the solvent from THF to Et 2 O or the counterion from Li + to MgCl + . This reactivity change is due to a large change in the structure of the acylate complex with a different counterion or solvent, as determined by IR and 13 C NMR spectroscopy and by oxidation potentials. In contrast, when a heteroatom nucleophile is used, such as a dialkyl amide or an alkoxide, the effect of a change in solvent or counterion on the structure, and therefore on the reactivity of the acylate complex, is minimal.