Diastereoselective photochemical radical addition of a cyclic ether to olefins: addition of THF radicals to dialkyl maleates.

The diastereoselectivity of the addition reaction of a THF radical to dialkyl maleates, the stereochemistry of the carbon atoms at both sides of the newly formed C-C bonds, has still not been established; both the presence and absence of diastereoselectivity have been reported in previous studies and its origin has not been discussed. We have obtained clear evidence for the presence of diastereoselectivity in the addition reaction, in which the diastereoselectivity increases with an increase in the bulkiness of the alkyl groups. DFT calculations on the maleates showed the presence of one or two stable conformations, which depend on the bulkiness of the alkyl groups. [ABSTRACT FROM AUTHOR]