作者:John D. Price、Richard P. Johnson
DOI:10.1021/jo00022a029
日期:1991.10
The singlet and triplet photoreactions of 1-tert-butyl-1,2-cyclooctadiene (1) are described. This is the first example of an isolable eight-membered ring allene and is predicted to have a bent allenic unit. Triplet reactions of 1 are phase dependent. Benzene-sensitized irradiation affords products of hydrogen abstraction at tert-butyl or ring carbons in vapor phase or solution phase, respectively. Direct irradiation of thoroughly degassed pentane solutions at 254 nm affords primarily 3-tert-butylbicyclo[3.3.0]oct-2-ene and other products that are attributed to initial excited-state 1,2-hydrogen migration to a vinylcarbene. Independent generation of this vinylcarbene gives a similar collection of products, which include an isolable bicyclo[5.1.0]oct-1(8)-ene. Irradiation of 1 in oxygenated solutions yields tert-butylcycloheptene (15), apparently through loss of carbon monoxide from an intermediate cyclopropanone. Oxidation of 1 with m-CPBA also leads efficiently to 15.