(Nitrosyl)(salen)ruthenium(II) complex 1 was found to serve as an efficient
catalyst for the epoxidation of conjugated olefins under photoirradiation,
with 2,6-dichloropyridine N-oxide (2) or tetramethylpyrazine N,N'-dioxide
as a stoichiometric oxidant. High enantioselectivity was achieved irrespect
ive of the substitution pattern of olefins. The choice of solvent depends o
n stability of the resulting epoxides: high enantioselectivity is generally
observed in the reaction with ethereal solvents, but use of benzene is rec
ommended when the resulting epoxides are acid-sensitive.