The reaction of triphenylstannylcobaloxime with enynes under photochemicaland thermal conditions

Enynes having the 4-oxa-6-en-1-yne, 4-tosylaza-6-en-1-yne and 5-oxa-7-en-1- yne system, and 5,7-dioxa-1-octyne were reacted with triphenylstannylcobalo xime, which is a source of the triphenylstannyl radical and cobaloxime radi cal. The reaction pattern is different under photochemical and thermal cond itions. Photochemical reaction gave the products formed by the addition of the triphenylstannyl radical to the acetylene group followed by the tandem addition of the intermediate vinyl radical to the intramolecular olefin. Th ermal reaction gave triphenylstannyl-substitution products at the terminal position of the acetylene moiety. Thus, the photochemical reaction takes a free radical pathway, and the thermal reaction is proposed to take a single electron transfer mechanism. (C) 2000 Elsevier Science B.V. All rights res erved.