Diastereoselective ring opening of limonene oxide with water catalysed by beta-ketophosphonate complexes of molybdenum(VI)

In the presence of catalytic quantities of [MoO2Cl2L] (L=beta-ketophosphona te derived from camphor), water initiates the selective ring opening of cis (+) or (-)-limonene oxide to give the trans-diaxial diol. The trans isomer of the limonene oxide remains almost completely unreacted, thus providing a method for the kinetic separation of the trans diastereomer. H-1 and C-13 NMR studies of the interaction of the epoxide with the molybdenum complex show that the metal coordinates to the epoxide oxygen atom and that the dia stereo-discriminating step is attack of Mo=O onto the tertiary carbocation formed by cleavage of a C-O bond in the epoxide. (C) 1999 Elsevier Science Ltd. All rights reserved.