Photochemistry of alkenes. 9. Medium-sized cycloalkenes

Abstract

985). The behavior of the three medium-sized cycloalkenes cyclooctene (lo), cyclodecene (17), and cyclododecene (21) on direct irradiation in pentane and methanol solution has been studied. The results are summarized in Tables 1-3. Irradiation of medium-sized cycloalkenes is a convenient procedure for the preparation of bicyclic products (cf. 13, 14, 19, 20, and 23) through transannular insertion reactions of carbene intermediates (cf. 11, 18, and 22) thought to arise from rearrangement of the '[-rr,R(3s)] state via a 1,2-hydrogen shift. The formation of trans-decalin (20) is in contrast to the reported formation of the cis isomer on base-initiated decomposition of the corresponding tosylhydrazone. None of the three cycloalkenes 10, 17, or 21 underwent competing nucleophilic trapping of the '[-rr,~(3s)] state in methanol, in contrast with other alkenes previously studied. However, cyclododecene (21) afforded the methyl ether 25, which apparently resulted from protonation of the '(-rr,-rr*) state, and the epoxide 26, which is thought to arise from electron transfer to oxygen by the '[-rr,R(3s)] state followed by protonation of the resulting superoxide ion and oxidation of unreacted cyclododecene (21). PAUL J . KROPP, J. DEREK MASON et GARDINER F. H. SMITH. Can. J. Chem. 63, 1845Chem. 63, (1985. Operant dans des solutions dans le pentane ainsi que dans le mCthanol, on a Ctudit le comportement, vis-a-vis de I'irradiation directe, des trois cycloalk&nes a cycles moyens suivants: cycloocttne (lo), cyclodCcbne (17) [Traduit par le journal]

Construction of Bicyclic Ring Systems via a Transannular SmI2-Mediated Ketone−Olefin Cyclization Strategy

“…18,19 Transannular transformations appear in the chemical literature rather sporadically, mainly in connection with method development as isolated examples of a general, nontransannular process. [20][21][22][23][24][25][26][27][28][29][30][31][32] A small number of (1) Molander, G. A.; Etter, J. B. Tetrahedron Lett.…”

“…A thorough examination of the literature reveals that besides the transannular Diels−Alder reaction, this strategy has not been systematically studied. , Transannular transformations appear in the chemical literature rather sporadically, mainly in connection with method development as isolated examples of a general, nontransannular process. − A small number of examples were also found in which transannular transformations were utilized in natural product synthesis. − …”