Five-Coordinate [RuCl(P−P*)₂]⁺Complexes Containing Chiral Diphosphines:  Application in the Asymmetric Cyclopropanation and Epoxidation of Olefins

Abstract

The six-coordinate complexes trans-[RuCl2(P−P*)2] (P−P* = (S,S)-1,2-bis(1-naphthylphenylphosphino)ethane (bnpe), 2a; (S,S)-2,3-bis(diphenylphosphino)butane (chiraphos), 2b) have been prepared and structurally characterized. The X-ray studies of 2a,b show non-C 2-symmetric conformations of the substituents at the PPh2 groups in a highly crowded octahedral environment. Complexes 2a,b react with Tl[PF6] in CH2Cl2 to give the corresponding monochloro, cationic derivatives [RuCl(P−P*)2]PF6 (P−P* = bnpe, 3a; chiraphos, 3b). The bnpe derivative 3a is five-coordinate both in the solid state (by X-ray investigation) and in solution (by 31P NMR spectroscopy). The chiraphos analogue 3b apparently dimerizes in solution, depending on the solvent (CDCl3 or CD2Cl2) and on the concentration. Complexes 3a,b catalyze the decomposition of ethyl diazoacetate to give, in the presence of styrene, the corresponding cyclopropanation products with enantioselectivity up to 35% ee and E/Z ratios of about 55:45. Complexes 3a,b also catalyze the epoxidation of unfunctionalized olefins with iodosyl benzene as the primary oxidant. High olefin conversions and fair selectivity for the epoxide are observed, but both 3a and 3b give racemic epoxide.

Ruthenium‐Catalyzed Asymmetric Epoxidation of Olefins Using H2O2, Part II: Catalytic Activities and Mechanism

“…In general, after 12 h of addition of H 2 O 2 good yield for the epoxidation of styrene and an excellent yield for that of trans-stilbene are obtained. It is worth noting that aryl groups on the C4-position generally gave a better reactivity towards styrene than alkyl groups (Table 1, entries 1-16 and entries [18][19][20][21][22]. When a highly sterically demanding group is introduced, either on the C4-or C5-position, the reactivity dropped tremendously (Table 1, entries 17 and 20).…”

A simple synthesis of trans-RuCl(CCR)(dppe)2 complexes and representative molecular structures

“…Crystallographic data and important bond lengths and angles are summarized in Tables 3 and 4, with plots of [2] [78]. The cation in [2]OTf is essentially identical to that in [2]PF 6 and [2]BF 4 with a similar degree of ''Y"-shaped distortion of the equatorial plane from that in an idealised trigonal bipyramid.…”

Better Performance of Monodentate P‐Stereogenic Phosphanes Compared to Bidentate Analogues in Pd‐Catalyzed Asymmetric Allylic Alkylations

“…Phosphanes 1a and 2a have already been reported by Mezzetti and coworkers. [29,30] The mixtures can be purified by column chromatography. Starting from monodentate phosphanes of the S-absolute configuration, the diphosphanes 1 and 2 are expected to retain the same configuration (S,S) as reported for analogous ligands.…”