Tandem ROMP−Hydrogenation with a Third-Generation Grubbs Catalyst

Tandem ROMP−hydrogenation enables efficient access to saturated, functionalized “ROMP polyolefins”. Of the Grubbs-class initiators 1−3, only third-generation catalyst 3 enables efficient ROMP of sterically demanding norbornenes with precise specification of chain lengths. Unlike 1 and 2, however, 3 decomposes rapidly during subsequent hydrogenation. By trapping the propagating species with PCy3 immediately following ROMP, we generate a Ru-terminated chain identical to that formed from 2 and exhibiting equivalent hydrogenation activity. The remarkable ROMP efficiency of 3 can thus be integrated with the high hydrogenation activity of 2, providing efficient access to chain-length-precise, functionalized polyolefins.