Potassium tert‐Butoxide‐Catalyzed Dehydrogenative Si-O Coupling: Reactivity Pattern and Mechanism of an Underappreciated Alcohol Protection

Abstract

As simple as it gets! Potassium tert-butoxide alone catalyzes the direct dehydrogenative SiO coupling of several synthetically important silanes with 1°, 2°, and even 3° alcohols without the need for stoichiometric hydrochloric acid scavengers. The stereoretentive mechanism is probed with a silicon-stereogenic silane. A remarkable tert-butoxide-catalyzed coupling of alcohols and silanes is reported. Dihydrogen and not hydrochloric acid (generated in the prevalent, related coupling of alcohols and chlorosilanes) is formed as the sole by-product. A comprehensive survey of common silanes provides a reliable tool for the predictability of their reactivity under defined reaction conditions. The debated mechanism of this transformation is investigated monitoring the stereochemical course at the silicon atom by means of a silicon-stereogenic silane. On this basis, a transition state for the enantiospecific SiO coupling step is suggested rationalizing the observed frontside attack and thus retention at the silicon atom.