Schwartz reagents: methods of in situ generation and use

摘要

Embodiments of the invention provide a method of using Schwartz Reagent, Cp₂Zr(H)Cl, without accumulating or isolating it. Methods provide mixtures of Cp₂ZrCl₂, reductants that selectively reduce Cp₂ZrCl₂, and substrates. After reaction of Cp₂ZrCl₂ and the reductant, an intermediate reduction product is formed, apparently Schwartz Reagent. The in situ Schwartz Reagent then selectively reduces certain functional groups on the substrate. Substrates include tertiary amides, tertiary benzamides, aryl O-carbamates, and heteroaryl N-carbamates, which are reduced to aldehydes, benzaldehydes, aromatic alcohols, and heteroaromatics, respectively. Compared to prior methods, reagents are inexpensive and stable, reaction times are short, and reaction temperature in certain cases is conveniently room temperature. It has been estimated that using the in situ method described herein instead of synthesized or commercially obtained Schwartz Reagent provides a 50% reduction in cost.