Asymmetric photosensitized addition of methanol to (R)-(+)-(Z)-limonene in a microreactor

Photosensitized diastereodifferentiating addition of methanol to (R)-(+)-(Z)-limonene in a microreactor was investigated. The quantity of photoproducts, cis- and trans-4-isopropenyl-1-methoxy-1-methylcyclohexane, increases with increasing period of irradiation by a mercury lamp, and the diastereomeric excess (de) of the photoadduct is slightly larger than that obtained in a batch reaction system. The reaction rate constants for the production of the cis and trans isomers were successfully obtained by using the steady state approximation. The larger de value in the microreactor was found to result from the suppression of the sequential side reaction processes. The feasibility of microreaction system for the photoreaction will be discussed.