Room temperature operating allenylidene precatalyst [LnRu = C = C = CR2](+)X- for olefin metathesis: dramatic influence of the counter anion X-

摘要

The allenylidene-ruthenium(II) complex [(p-cymene)(PCy3)Cl-Ru=C=C=CPh2]X-+(-), 2a, (X- = CF3SO3-), which is produced in a one-pot reaction from commercially available [RuCl2(p-cymene)](2), catalyses the ring-closing metathesis of N,N-diallyltosylamide at room temperature whereas 2b (X- = BF4-) favours the cyclization of the 1,6-diene 3 into the five-membered heterocycle 5 without loss of atoms. The addition of BF3. OEt2 to 2b restores its selectivity in the RCM reaction. Catalyst 2a also promotes the metathesis of the ene-yne 6 to produce the 3-vinyl-2,5-dihydrofuran 7. [References: 30]