A ROMP-derived, polymer-supported chiral Schrock catalyst for enantioselective ring-closing olefin metathesis

Abstract

A permanently polymer-immobilised version of Schrock's molybdenum catalyst was realised via polymerisation of chiral 5,5′-bis(norborn-5-ene-2-ylmethyleneoxymethyl)-3,3′-di-tert-butyl-6,6′-dimethylbiphen-2,2′-diol followed by reaction with the catalyst precursor Mo(N-2,6-i-Pr₂C₆H₃)(CHCMe₂Ph)(OSO₂CF₃)₂(CH₃OCH₂CH₂OCH₃); using this 5-, 6- and 7-membered heterocycles were synthesised via ring-closing metathesis (RCM) from (pro-)chiral substrates in high yields and ee with short reaction times; the catalyst shows low loss of molybdenum during RCM, and was easily separated and recycled.