Intramolekulare reaktionen von vinyl- und allyl-phosphoryl-carbenen (1)

Photochemical transformations of small ring compounds. 95. The problem of regioselectivity in the photochemical ring-opening reaction of 3-phenyl- and 3-vinyl-substituted cyclopropenes to indenes and 1,3-cyclopentadienes

“…In order to establish this possibility, a number of 3-vinyl-substituted diarylcyclopropenes were prepared by treating variously substituted cyclopropenyl cations with vinyl Grignard reagents and separating the mixture of isomers formed by column chromatography. Although indenes are generally formed from the irradiation of 3 -arylsubstituted cyclopropenes, the photolysis of l,2,3-triphenyl-3-vinylcyclopropene (22) resulted…”

“…Preparation of l,2,3-Triphenyl-3-vinyleyclopropene (22). A 0.7-M solution of vinylmagnesium bromide in 100 mL of tetrahydrofuran was slowly added to a suspension of triphenylcyclopropenyl perchlorate85 in 250 mL of tetrahydrofuran at -78 °C.…”

“…Irradiation of l,2,3-Triphenyl-3-vinylcyclopropene (22). A solution containing 354 mg of 22 in 400 mL of benzene was irradiated with a 550-W Hanovia lamp equipped with a Pyrex filter sleeve for 5 h. Removal of the solvent followed by thick-layer chromatography gave 250 mg (70%) of a crystalline solid, mp 157-158 °C, whose structure was assigned as 1,2,3-triphenylcyclopentadiene (23): IR (KBr) 3.10, 6.25, 6.68, 6.95, 7.28, 8.25, 9.34, 9.73,10.24,10.84,10.95, 11.28,11.44,12.95,13.16,13.56,14.41 µ ; UV (95% ethanol) 305 nm (e 11 000), 246 (30 200); NMR (CDCI3,60 MHz) 6.40 (d, 2 H, J = 2.0 Hz), 3.48 (t, 1 H, J = 2.0 Hz), 2.70-3.0 (m, 15 H).…”

Photochemistry of the diazonium and diazo groups

“…(198) (1 99) niethoxy(trimethy1)silane is the major product in methanol, 1,2-methyl migration becomes more rapid in r -b u t a n 0 1~~~. (198) (1 99) niethoxy(trimethy1)silane is the major product in methanol, 1,2-methyl migration becomes more rapid in r -b u t a n 0 1~~~.…”

Chemistry of Phosphorylcarbenes

“…Cyclopropanations with phosphoryldiazoalkanes by the carbenoid route are more clear-cut and usually give a very high yield (Table 3); the H-abstraction that dominates on photochemical production of the carbenes is wholly suppressed. Usually the diazo compounds are decomposed on catalysis by copper [(46)-- (49)]; it is surprising that cyclopropanation of 3-(trimethylsilyl)propene with ( I ) , to yield (4.5), occurs already at CL2O"C. The stereochemistry at the phosphoryl-carbon atom of the cyclopropanes is known only for (46)['01.…”