Living ROMP of Disubstituted Cyclopropenes

Significance

Schrock and co-workers report the first living ring-opening polymerization (ROMP) of cyclopropenes. 3,3-Disubstituted cyclopropenes were polymerized in one hour at room temperature in high yields using molybdenum-based catalysts. The resulting polymers exhibited low polydispersity, high trans selectivity, and low tacticity. Diblock and triblock copolymers with a variety of bicyclic comonomers were also prepared in high yield (>90%) and low polydispersity. Notably, a cyclopropene substituted with a polar functional group [i.e., 3-(2-methoxyethyl)-3-methylcyclo­propene] was successfully polymerized. In situ ¹H NMR spectroscopic studies revealed rapid and complete initiation for catalysts 2 and 3. In contrast, the 2^nd generation Grubbs ruthenium catalyst required 15 hours for complete initiation under the same reaction conditions.