Abstract
Development of versatile ruthenium olefin-metathesis catalysts with high activity, stability, and selectivity is a continuous challenge. Here we report highly controllable ruthenium catalysts using readily accessible and versatile N-vinylsulfonamides as carbene precursors. Catalyst initiation rates were controlled in a straightforward manner, from latent to fast initiating, through the facile modulation of the N-vinylsulfonamide ligands. Trifluoromethanesulfonamide-based catalysts initiated ultrarapidly even at temperatures as low as −60 °C and continuously propagated rapidly, enabling the enthalpically and entropically less-favored ring-opening metathesis polymerizations of low-strained functionalized cyclopentene derivatives, some of which are not accessible with previous olefin-metathesis catalysts. To our surprise, the developed catalysts facilitated the polymerization of cyclopentadiene (CPD), a feedstock that is easily and commonly obtainable through the steam cracking of naphtha, which has, to the best of our knowledge, not been previously achieved due to its low ring strain and facile dimerization even at low temperatures (below 0 °C).
Highlights
Development of versatile ruthenium olefin-metathesis catalysts with high activity, stability, and selectivity is a continuous challenge
Fast-initiating catalysts are especially useful for selective metathesis[25,30], controlled living ROMP26,35, and ring-opening metathesis polymerization (ROMP) of low-strained monomers[9,34], whereas slow-initiating catalysts are beneficial for industrial molding process involving the ROMP of highly constrained monomers such as DCPD and orthogonal metathesis reactions[31,32,33,36]
On the basis of this versatile scaffold, more than ten catalysts were prepared. These catalysts exhibited initiation rates that were controlled in a straightforward manner by modifying their steric and electronic characteristics
Summary
Development of versatile ruthenium olefin-metathesis catalysts with high activity, stability, and selectivity is a continuous challenge. The developed catalysts facilitated the polymerization of cyclopentadiene (CPD), a feedstock that is and commonly obtainable through the steam cracking of naphtha, which has, to the best of our knowledge, not been previously achieved due to its low ring strain and facile dimerization even at low temperatures (below 0 °C). Fast-initiating catalysts are especially useful for selective metathesis[25,30], controlled living ROMP26,35, and ROMP of low-strained monomers[9,34], whereas slow-initiating catalysts are beneficial for industrial molding process involving the ROMP of highly constrained monomers such as DCPD and orthogonal metathesis reactions[31,32,33,36]. In 2002, Louie and Grubbs[37] reported that electron-rich carbene-based Ru complexes can slowly initiate the catalysis of a ROMP RCM
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