Organic-solvent-free cross-couplings between benzylic and alkenyl halides have been developed. Various alkenyl halides can be effciently benzylated by combining the precursor halides in the presence of Zn dust and a Pd catalyst at room temperature, in water as the only medium.

A mild and environmentally attractive dehalogenation of functionalized aryl halides has been developed using nanoparticles formed from PdCl2 in the presence of tetramethyldisiloxane (TMDS) on water. The active catalyst and reaction medium can be recycled. This method can also be applied to cascade reactions in a one-pot sequence.

Well-established, traditional Kumada cross-couplings involve preformed Grignard reagents in dry ethereal solvent that typically react, e.g., with aryl halides via Pd catalysis to afford products of net substitution. Therefore, in the work described, which appears to be counterintuitive, exposure of these same aromatic halides to catalytic amounts of Pd(II) and excess magnesium metal in pure water leads to symmetrical/unsymmetrical biaryls, indicative of a net Kumada-like biaryl coupling. Evidence is presented suggesting that Grignard reagents, formed in situ in water, may be involved.

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Alkenyl Halides.-A novel method is elaborated for the preparation of (Z)-and (E)-allylbenzenes (III) and (VI), resp., in an aqueous media. The analogous procedure is applied for benzylation and two-step dibenzylation of bromostyrene (XI). -(KRASOVSKAYA, V.; KRASOVSKIY, A.; BHATTACHARJYA, A.; LIPSHUTZ*, B. H.; Chem. Commun. (Cambridge) 47 (2011) 20, 5717-5719, http://dx.