Photochemical transformations of small ring heterocyclic compounds. 71. Intramolecular 1,1-cycloaddition reactions of nitrile ylides

Interconversion of dipoles by the flash vacuum pyrolysis of oxadiazolinones

“…Removal of the solvent under reduced pressure left 0.62 g of a clear oil, which was chromatographed on a silica gel column using hexane as the eluent. The first fraction obtained was identified as trans-1 -phenyl-1,3-butadiene (8) on the basis of its spectral properties and by comparison with an authentic sample:39 IR (neat) 3.25, 3.27, 3.30, 6.14, 6.24, 6.71, 6.92, 7.70, 8.62, 9.40, 9.81, 10.05, 10.60, 11.20, 11.74, 13.21, and 14.20 Mm; NMR (CDC13, 60 MHz) b 5.0-5.4 (m, 2 H), 6.1-6.8 (m, 3 H), and 7.0-7.4 (m, 5 H). The second fraction isolated from the column was identified as 2-phenyl-1,3-butadiene (7) on the basis of its spectral properties and by comparison with an authentic sample:40 IR (neat) 3.20, 3.24, 3.33, 5.90, 6.22, 6.29, 6.35, 6.68, 6.91, 7.92,9.30.…”

Azirine photochemistry

“…Thus, treatment of o -allyl-substituted imidoyl chloride 51 with triethylamine gave benzobicyclo[3.1.0]hex-2-ene 52. 54 Irradiation of the closely related methyl-substituted azirine system 53 gave a mixture of endoand exobenzobicyclohexenes (54) in quantitative yield.54 No detectable quantities of the isomeric 1,3-dipolar adduct was observed in either system. In the case of 53, the major product (exo-54) is the thermodynamically more favored exo isomer.…”

Studies on the intramolecular addition of vinyl nitrenes to olefins

“…The material isolated in the first band contained a 1:1 mixture of isomeric 2-phenyl-3-methyl-5-(2-propenyl)-A,-pyrrolines (17). Isomer A: NMR (CC14,100MHz) 8.82 (d, 3 H, J = 7.5 Hz), 8.26 (s, 3 ), 8.12 (t, 1 H, J = 8.0 Hz), 8.08 (t, 1 H,J~8 .0 Hz), 6.55 (m, 1 H), 5.42 (broad t, 1 H, J = 8.0 Hz), 5.22 (broad s, 1 H), 5.Ó5 (broad s, 1 ), 2.0-2.8 (m, The other isomer (B) showed the following spectral properties: NMR (CC14, 100 MHz) r 8.81 (d, 3 H, J = 7.0 Hz), 8.19 (s, 3 ), 8.07 (m, 1 ), 7.50 (dt, 1 H, J = 12.0, 8.0 Hz), 6.58 (m, 1 H), 5.44 (dd, 1 H, J = 8.0, 7.0 Hz), 5.20 (broad s, 1 ), 5.11 (broad The second band from the thick-layer plate contained a clear oil (60%) whose structure was assigned as l,4,4-trimethyl-2-phenyl-3azabicyclo[3.1.0]hex-2-ene ( 16) on the basis of its spectral data: NMR (CCU, 100 MHz) 9.44 (t, 1H, J = 4.0Hz), 9.20 Thermolysis of Methyl 4-(2-Methyl-3-phenyl-2ii-azirin-2yl)-2-butenoate (18). A solution containing 75 mg of (£)or (Z)azirinyl-2-butenoate 1842 in 10 mL of toluene was heated in a sealed tube at 180 °C for 124 h. Removal of the solvent under reduced pressure left a yellow oil which was subjected to thick-layer chromatography.…”

“…A solution containing 100 mg of azirine T' in 10 mL of toluene was heated at 195 °C in a sealed tube for 166 h. Removal of the solvent left a yellow oil which was subjected to thick-layer chromatography using a 1:2 mixture of ether-cyclohexane as the eluent. The first fraction (21%) contained an inseparable mixture (1:1) of the cis and trans isomers of 2-phenyl-3-methyl-5-vinyl-A1-pyrroline (9): NMR (CC14,100 MHz) 8.82 and 8.84 (two doublets, 3 H, J = 7.0 Hz), 8.4-S.7 (m, 1 ), 8.10 (m, 1 H), 6.64 (m. 1 ), 5.40 (m, 1 ), 4.7-5.1 (m, A 100-mg sample of A'-pyrroline 9 in 50 mL of toluene containing 100 mg of 5% palladium on carbon was heated at reflux for 48 h. Removal of the catalyst followed by evaporation of the solvent left 93 mg of 2-phenvl-o-methyl-5-ethylpyrrole (11): NMR (CC14,100 MHz) r 8.79 (t, 3 H,V =--8.0 Hz), 7.81, (s, 3 H), 7.44 (q, 2 H, J = 8.0 Hz), 4.32 (d, 1 H, J = 3.0 Hz, collapsed to a singlet with D2O wash), 2.6-3.0 (m, 5 ), 2.0-2.6 (1 H, broad s, exchanged with D2O); IR (neat) 3420,3050, 2960, 2920, 2860, 1600, 1510. 1485, 1440, 1375, 1335, 1140, 800, 760, 695, 640 cm"1; MS m/e 185 (M+), 170, 147,105, 77. Anal.…”

“…Flash thermolysis of the same tetrazoles 2 at 800 °C (10-3 mm) gives 2,6-disubstituted fluorenes 7 (2,6 substituents = H or CH;¡) or 3azafluorene (7e) in yields of 90-100%. The thermolysis of 3-phenylpyrazolo [3,4-b]pyridine (8) at 770 °C resulted in a 49% conversion to 4-azafluorene (9). Thermolysis of 2,4-diphenyl-l,3,4-oxadiazolin-5-one (16a) at 500 °C (10"2 mm) gave 3-phenylindazole (94%); at 750 °C fluorene was obtained (84%).…”