“…13 C NMR [125.8 MHz, acetone-d 6 ]: δ 67.9 (CH 2 ), 68.8 (CH 2 ), 88.3 (C-6), 92.4 (d, 3 J C,F = 3.0 Hz, C-4), 92.9 (d, 2 J C,F = 39.5 Hz, C-3), 106.4 (C6a), 121.7 (C-2), 123.6 (d, 1 J C,F = 272.1 Hz, CF 3 ), 124.3 (d, 4 J C,F = 1.4 Hz, C-5), 134.8 (C-2a), 190.5 (C-1), 228.2 (CO) ppm. MS: m/z (%) 380 (13) [M + ], 352 (19) [M + − CO], 324 (16) [M + − 2CO], 296 (73) [M + − 3CO], 277 (10) [M + − 3CO − F], 268 (37) [M + − 4CO], 225 (12), 216 (17) [M + − 4CO − Cr], 196 (100) [(F 3 CC 6 H 3 Cr) + ], 172 (36), 162 (38), 155 (11), 150 (54), 144 (38), 134 (24), 125 (56), 115 (19), 106 (95) [(FCC 6 H 3 ) + ], 103 (50), 87 (78) [C 7 H 3 ) + ], 75 (53) Unsuccessful Attempts toward 1,1,2,2-Tetramethoxy-3-(trifluoromethyl)benzocyclobutene (32). (a) At 0 °C trimethoxymethane (0.6 mL, 5.0 mmol) was added to 6-(trifluoromethyl)benzocyclobutenedione (10; 0.10 g, 0.5 mmol) in methanol (1 mL).…”