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Asymmetric Cyclization of Propylene Chlorohydrins Catalyzed by an Optically Active Cobalt(salen) Type Complex

1979; Oxford University Press; Volume: 52; Issue: 9 Linguagem: Inglês

10.1246/bcsj.52.2614

1348-0634

Tsutomu Takeichi, Michihiro Ishimori, Teiji Tsuruta,

Surface Chemistry and Catalysis

Abstract By using an optically active cobalt complex, N,N′-disalicylidene-(1R,2R)-1,2-cyclohexanediaminatocobalt(II), as a catalyst, optically active methyloxirane was synthesized by the asymmetric elimination of hydrogen chloride with a base from racemic propylene chlorohydrins. The highest optical purity of methyloxirane so far obtained was 35%, observed when 2-chloro-1-propanol and potassium carbonate were used as substrate and base, respectively. The optical rotations of the products and of the unchanged substrates indicate that (S)-1-chloro-2-propanol reacted selectively to produce (S)-methyloxirane, whereas in the case of 2-chloro-1-propanol, the (R)-isomer was preferentially cyclized to give (S)-methyloxirane with inversion of the asymmetric carbon. The physicochemical data of the circular dichroism and absorption spectra indicated a complexation of the optically active cobalt(II) species with potassium carbonate, either the (R)- or (S)-substrate interacting selectively with the Co*/K2CO3complex formed, followed by cyclization of the substrate.