Generation of chiral 3,8-methano[11]annulenylidene. Stereochemical and mechanistic implications

Crystal structure of 5,6,11,12-tetradehydrodibenzo[a,e]cyclooctene (sym-dibenzo-1,5-cyclooctadiene-3,7-diyne)

“…and coworkers2 reported that the gas-phase pyrolysis (550°, Na flow) of phenyltrimethylsilyldiazomethane (1) afforded benzosilacyclopentene (4) and that this product was evidence for the intermediacy of silacyclopropane (3), which resulted from the intramolecular insertion of carbene 2 into a C-H bond of a methyl group (Scheme I).…”

Generation and properties of 4,9- and 3,8-methano[11]annulenylidenes

“…Recrystallization of 100 mg from 3 mL of methanol gave a sample with the same melting point. Spectral data: IR (KBr) 3400, 3140, 2900, 2930, 1590, 1435, 1355, 1305, 1155, 1080, 1035,925,890,800,760,650, 565,550 cm-'; NMR (CDC13) 8.09-6.98 (m, 12 H), 2.37 (s, 3 H), 0.28 ('/2( + ß) (AB system, 2 , AB « 9 Hz) N-H (s) varies; exact mass 338.1088 (caled for C,9H,8N202S, 338.1088).…”

“…Blcyclo(5.4.1]dodeca-2,5,7,9,ll-pentaene (8). Dry diglyme (50 mL) was saturated with N2 and then heated to 130 °C under a N2 atmosphere.…”

“…Chemistry of 4,9-Methano[l l]annulenylidene and Some of Its Products. When generated from 6 the chemical behavior of this intermediate (summarized in Scheme III) is remarkably similar to the 6-Tr-electron system cycloheptatrienylidene 22.4'19 Thus, in the absence of a reactive substrate it dimerizes 22 to the fulvalene 8 (stereochemistry unknown). In the presence of an electron-deficient trap such as dimethyl fumarate, it adds to give the spirocyclopropane 18 which, as in the analogous spirononatriene system,19 isomerizes in the presence of acid to give the corresponding fulvene 19. The carbene also adds to styrenes to give the spirocyclopropanes 17 (mixtures of stereoisomers).…”