Deoxygenative Metal Carbenation: A Strategy for Stereocontrolled Olefin Metathesis via an Oxo-Ruthenium Precursor

Abstract

Dithiolene metathesis catalysts have enabled breakthroughs in materials and medicinal contexts in which control of cis/trans alkene stereochemistry translates into control over function. Their extreme air-sensitivity, however, impedes widespread uptake. Building on the discovery that air-exposure selectively decomposes the leading catalyst Ru(S–S)(H2IPr)(═CHAr) (Ru-1a; S–S = 1,2-S2C6H2-3,6-Cl2, Ar = C6H4-2-OiPr) into four-coordinate oxo complex Ru-2 Ru(O)(S–S)(H2IPr), we demonstrate that the latter offers convenient access to Ru-1a and related catalysts via reaction with phosphorus ylides (Ph3P═CHR; R = Ar, Ph, H). This “deoxygenative metal carbenation” (DMC) strategy opens new opportunities in olefin metathesis. Beyond regeneration of Ru-1a after decomposition, it enables direct, tunable access to more active on-cycle species (potentially including tagged benzylidenes) from a robust, shelf-stable precursor. In situ generation of these well-defined active species confers metathesis activity and stereocontrol comparable to or better than pristine, meticulously handled Ru-1a, and far superior to samples of Ru-1a even briefly exposed to air in solution. In eliminating the need for production, shipping, and storage of air-sensitive Ru-1a, this advance is anticipated to expand the uptake of olefin metathesis for production of stereodefined alkenes.