Toggle Main Menu Toggle Search

Open Access padlockePrints

Kinetics and mechanism of vanadium catalysed asymmetric cyanohydrin synthesis in propylene carbonate

Lookup NU author(s): Professor Michael North, Marta Omedes Pujol


Full text for this publication is not currently held within this repository. Alternative links are provided below where available.


Propylene carbonate can be used as a green solvent for the asymmetric synthesis of cyanohydrin trimethylsilyl ethers from aldehydes and trimethylsilyl cyanide catalysed by VO(salen)NCS, though reactions are slower in this solvent than the corresponding reactions carried out in dichloromethane. A mechanistic study has been undertaken, comparing the catalytic activity of VO(salen)NCS in propylene carbonate and dichloromethane. Reactions in both solvents obey overall second-order kinetics, the rate of reaction being dependent on the concentration of both the aldehyde and trimethylsilyl cyanide. The order with respect to VO(salen)NCS was determined and found to decrease from 1.2 in dichloromethane to 1.0 in propylene carbonate, indicating that in propylene carbonate, VO(salen)NCS is present only as a mononuclear species, whereas in dichloromethane dinuclear species are present which have previously been shown to be responsible for most of the catalytic activity. Evidence from V-51 NMR spectroscopy suggested that propylene carbonate coordinates to VO(salen)NCS, blocking the free coordination site, thus inhibiting its Lewis acidity and accounting for the reduction in catalytic activity. This explanation was further supported by a Hammett analysis study, which indicated that Lewis base catalysis made a much greater contribution to the overall catalytic activity of VO(salen)NCS in propylene carbonate than in dichloromethane.

Publication metadata

Author(s): North M, Omedes-Pujol M

Publication type: Article

Publication status: Published

Journal: Beilstein Journal of Organic Chemistry

Year: 2010

Volume: 6

Pages: 1043-1055

Print publication date: 03/11/2010

ISSN (electronic): 1860-5397

Publisher: Beilstein


DOI: 10.3762/bjoc.6.119


Altmetrics provided by Altmetric