General Information: Reagents were obtained from commercial supplier, and used without further purification unless otherwise specified by a reference. The pre-catalyst 3,3-dichloro-1,2-diphenylcyclopropene and ketoximes were prepared from 1,3diphenylacetone and ketones, respectively following reported procedures. 1,2 Solvents were purified by the usual methods and stored over molecular sieves. All reactions were performed using oven-dried glassware under a nitrogen atmosphere. Organic solutions

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... were concentrated using a Buchi rotary evaporator. Column chromatography was carried out over silica gel (Merck 100-200 mesh) and TLC was performed using silica gel GF254 (Merck) plates. Melting points were determined by open glass capillary method and are uncorrected. IR spectra in KBr were recorded on a Perkin-Elmer 993 IR spectrophotometer, 1 H NMR spectra were recorded on a Bruker AVII 400 spectrometer in CDCl 3 /DMSO-d 6 using TMS as internal reference with chemical shift value being reported in ppm. All coupling constants (J) are reported in Hertz (Hz). GC-MS were obtained on a Hewlett-Packard model GCD-HP1800A. General Procedure for Cyclopropenium Ion Catalysed Beckmann Rearrangement (Table 2) To a solution of ketoxime 1 (1 mmol) in dry acetonitrile (3 mL), 3,3-dichloro-1,2diphenylcyclopropene 2 (3 mol%) and ZnCl 2 (3 mol%) were added at rt and the reaction mixture was heated at reflux under a nitrogen atomosphere. After completion of the IR (KBr): ν max = H NMR (400 MHz, CDCl 3 ): δ = 7.82 (br, 1H), 7.54 (d, J = 8.0 Hz, 2H ), 7.28 (t, J = 7.5, 8.5 Hz, 2H), 7.10 (t, J = 7.5, 7.0 Hz, 1H), 2.35 (q, J = 7.5 Hz, 2H), 1.22 (t, J = 7.5 Hz, 3H). N-(2-naphthyl)acetamide (Table 2, Entry 7): Mp 132-134 °C, (Lit. 8 Mp 133-135 °C), IR (KBr): ν max = 3287, 1669, 1590, 1562, 1470, 1395, 1350, 1279, 856, 745 cm 1 ; 1 H NMR (400 MHz, CDCl 3 ): δ = 8.18 (br, 1H), 7.76-7.80 (m, 4H), 7.40-7.46 (m, 3H), 2.24 (s, 3H). N-phenylbenzamide (Table 2, Entry 8) Mp 162-163 °C, (Lit. 3 Mp 164-165 °C), IR (KBr): ν max = 3298, 3075, 3029, 1674, 1556, 1446, 735 cm 1 ; 1 H NMR (400 MHz, CDCl 3 ): δ = 7.91 (bs, 1H), 7.85-7.83 (m, 2H), 7.62 (d, J = 7.9 Hz, 2H), 7.54-7.49 (m, 1H), 7.46-7.43 (m, 2H), 7.37-7.31 (m, 2H), 7.14-711 (m, 1H). N-(4-fluorophenyl)benzamide and 4-fluoro-N-phenylbenzamide (Table 2, entry 9): Mp 168-180 °C, (Lit. 4 Mp 167-178 °C), IR (KBr): ν max = 3290, 3071, 3032, 1680, 1617, 1558, 1506, 1235, 837 cm 1 ; 1 H NMR (400 MHz, DMSO-d 6 ): δ = 10.32 (bs, 1H), 10.27 (bs, 1H), 8.07-8.02 (m, 2H), 7.96 (d, J = 7.0 Hz, 2H), 7.83-7.81 (m, 1H), 7.79-7.76 (m, 3H), 7.61-7.58 (m, 1H), 7.56-7.51 (m, 2H), 7.39-7.34 (m, 4H), 7.20 (t, J = 9.0 Hz, 2H), 7.13-7.09 (m, 1H).