Robust carbene ruthenium-porphyrin catalysts for cyclopropanation reaction of a wide variety of alkenes

Abstract

A series of carbene ruthenium-porphyrins [ Ru ( por )(: CR 1 R 2)] ( por = TPP ; R 1 = R 2 = p- C 6 H 4 Cl 2, p- C 6 H 4 Me 3, p- C 6 H 4 Ph 4; R 1 = Ph , R 2 = p- C 6 H 4 Ph 6; R 1 = Ph , R 2 = COPh 7; R 1 = p- C 6 H 4 Me , R 2 = CO (p- C 6 H 4 Me ) 8; R 1 = COMe, R 2 = COPh 9; por = TTP ; R 1 = R2 = Ph 1', COPh 5') were synthesized and characterized. The starting material [ Ru ( por )( CO )] was treated with corresponding diazo compounds N 2 CR 1 R 2 in CH 2 Cl 2 or octane for the diaryl carbene complexes 1', 2-4 and 6, while it was subjected to photolysis in THF , followed by reflux with the diazo compounds for the acyl carbene complexes 5' and 7-9. The compounds were robust in octane under reflux and were able to catalyze cyclopropanation reactions with methyl diazoacetate (MDA) toward a wide variety of alkenes. Monocyclopropanation of 25 alkenes was demonstrated with catalyst 3 in octane under reflux. By reaction with more than equimolar amounts of MDA in the presence of catalyst 9, the first porphyrin-catalyzed biscyclopropanation was attained toward nonconjugated α, ω-dienes, viz. 1,5-hexadiene and 1,7-octadiene.