[N+:1](=[C:3]([C:17]([CH3:19])=[O:18])[C:4]([O:6][CH2:7][C:8]1[CH:13]=[CH:12][C:11]([N+:14]([O-:16])=[O:15])=[CH:10][CH:9]=1)=[O:5])=[N-:2].C(N(CC)CC)C.FC(S(O[Si:35]([CH3:38])([CH3:37])[CH3:36])(=O)=O)(F)F>C(Cl)Cl>[N+:1](=[C:3]([C:17]([O:18][Si:35]([CH3:38])([CH3:37])[CH3:36])=[CH2:19])[C:4]([O:6][CH2:7][C:8]1[CH:9]=[CH:10][C:11]([N+:14]([O-:16])=[O:15])=[CH:12][CH:13]=1)=[O:5])=[N-:2]To a suspension of p-nitrobenzyl α-diazoacetoacetate (236 mg, 1 mmole) and triethylamine (0.15 ml, 1.08 mmole) in CH2Cl2 (2 ml) was added at 0°-5° C. trimethylsilyl trifluoromethylsulfonate (0.22 ml) under a nitrogen atmosphere and the mixture was stirred for 30 minutes. To this clear yellow solution was added dry hexanes (30 ml) and the reaction mixture was stirred for 10 minutes. After removing the oily deposit, the hexanes solution was evaporated in vacuo to yield yellow solid which was redissolved in dry hexanes (50 ml). The insoluble material was filtered over Celite and the filtrate was evaporated in vacuo to obtain 277 mg (0.90 mmole, yield 90%) of the title compound as yellow crystals: ir (film) νmax : 2100 (N2), 1705 (ester), 1520 and 1345 cm-1 (NO2); 1Hmr (CDCl3) δ: 0.27 (9H, s, --SiMe ), 4.23 (1H, d, J=2 Hz, vinyl proton), 4.93 (1H, d, J=2 Hz, vinyl proton), 5.32 (2H, s, --CO2CH2Ar), 7.48 (2H, "d", J=9 Hz, aromatic protons) and 8.23 ppm (2H, "d", J=9 Hz, aromatic protons).
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