Water-accelerated organic transformations

Rather than quenching all reactive intermediates and arresting the reaction , the addition of catalytic or stoichiometric (1-10 equiv.) quantities of H 2O to organic and organometallic processes can lead to surprisingly benefic ial effects on reaction rate, product yield, and regio-, diastereo- and ena ntioselectivity. A most intriguing aspect of H2O-promoted transformations i s the role that this strong Lewis-base can play in providing a source for m ore highly Lewis-acidic species. This scenario is most likely operative whe n H2O is added to reaction mixtures containing alanes, but organozinc reage nts or organocuprates also seem to be transformed accordingly. In addition, the oxide or hydroxide ligand on the metal presents a source for chelation interactions that change aggregation states of organometallics and can pro vide anchimeric assistance. In many cases, water has been found to be an ef fective hydrolyzing agent leading to secondary products that serve as catal ysts or promoters. In some cases, it has been shown that water provides a q uenching agent capable of driving chemical equilibria towards the desired p roducts.