- Dinuclear ruthenium(I) complexes of the type [Ru2(CO) 4L2] with carboxylate or 2-pyridonate ligands: Evaluation as catalysts for olefin cyclopropanation with diazoacetates
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Dinuclear ruthenium(I,I) carboxylate complexes [Ru2(CO) 4(μ-OOCR)2]n (R = CH3 (1a), C3H7 (1b), H (1c), CF3 (1d)) and 2-pyridonate complex [Ru2(CO)4(μ-2-pyridonate)2] n (3) catalyze efficiently the cyclopropanation of alkenes with methyl diazoacetate. High yields are obtained with terminal nucleophilic alkenes (styrene, ethyl vinyl ether, α-methylstyrene), medium yields with 1-hexene, cyclohexene, 4,5-dihydrofuran and 2-methyl-2-butene. The E-selectivity of the cyclopropanes obtained from the monosubstituted alkenes and the cycloalkenes decreases in the order 1b > 1a > 1d > 1c. The cyclopropanation of 2-methyl-2-butene is highly syn-selective. Several complexes of the type [Ru2(CO)4(μ-L1) 2]2 (4) and (5), [Ru2(CO)4(μ- L1)2L2] (L2 = CH3OH, PPh3) (6)-(9) and [Ru2(CO)4(CH 3CN)2(μ-L1)2] (10) and (11), where L1 is a 6-chloro- or 6-bromo-2-pyridonate ligand, are also efficient catalysts. Compared with catalyst 3, a halogen substituent at the pyridonate ligand affects the diastereoselectivity of cyclopropanation only slightly.
- Werle, Thorsten,Sch?ffler, Lutz,Maas, Gerhard
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p. 5562 - 5569
(2007/10/03)
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- Polymeric dicarbonyl ruthenium(I) acetate - An efficient catalyst for alkene cyclopropanation with diazoacetates
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The polymeric complex [Ru2(CO)4(μ-OAc)2](n) is the first Ru(I) catalyst that efficiently catalyzes cyclopropanation of alkenes with diazoacetic esters. The related dinuclear catalyst Ru2(CO)4(μ-OAc)2(MeCN)2 shows a similar performance only for cyclopropanation of monosubstituted alkenes.
- Maas,Werle,Alt,Mayer
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p. 881 - 888
(2007/10/02)
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- Reaction of Triplet Carbonyl Carbene with Olefins
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The gas-phase reaction of C2O(3Σ) with 2,3-dimethyl-2-butene produces 1,1,2,2,6,6,7,7-octamethyldispirooctane-4,8-dione and 2,2,3,3-tetramethylcyclopropanecarboxylic acid as major products rather than the allenic product characteristic of the reaction with simpler substrates.The positive identification of these molecules provides strong evidence for prior formation of the previously postulated cyclopropylideneketene.Further, the rate-determining step for reaction of C2O(3Σ) with the substrate cannot be elimination of CO as has been postulated on the basis of calculations.
- Parker, Garth,Wiseman, Douglas,Wintner, Claude,MacKay, Colin
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p. 4494 - 4497
(2007/10/02)
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- Novel process for the preparation of tetra-substituted cyclopropane compounds
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A process for the preparation of tetrasubstituted cyclopropane compounds of the formula STR1 wherein Y is selected from the group consisting of --CN and --COOR, R is selected from the group consisting of hydrogen and alkyl of 1 to 6 carbon atoms and R1, R2, R3 and R4 are individually selected from alkyl of 1 to 4 carbon atoms or R1 and R2 or R3 and R4 together with the carbon atoms to which they are attached form a carbon homocycle of 3 to 6 carbon atoms with the 2 substituents not forming the ring being alkyl of 1 to 4 carbon atoms or R1 and R2 on the one hand and R3 and R4 on the other together with the carbon atom to which they are attached form a carbon homocycle of 3 to 6 carbon atoms which are useful intermediates for the preparation of insecticidal esters and novel intermediates.
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