General procedure for the synthesis of 4-bromo-2-methyl-2,3-dihydro-1H-inden-1-one from the compound (CAS: 869063-66-1): a mixture of starting acid (unspecified amount) and 160 mL of thionyl chloride (SOCl2) was stirred for 24 hours at room temperature. Subsequently, the excess thionyl chloride was removed by distillation. Under vigorous stirring, crude 3-(2-bromophenyl)-2-methylpropionyl chloride (dissolved in 270 mL of dichloromethane) was added drop-wise to 1350 mL of dichloromethane suspension containing 136 g (1.02 mol) of aluminum trichloride (AlCl3), keeping the reaction temperature at 0 °C for 1 hour. After that, the reaction mixture was refluxed for 3 h, cooled to room temperature and poured into 500 mL of ice water. The organic layer was separated and the aqueous layer was extracted with methyl tert-butyl ether (3 x 300 mL). The organic phases were combined and dried over potassium carbonate (K2CO3) and subsequently evaporated to dryness. Purification by fractional distillation afforded 4-bromo-2-methyl-1-indanone with a boiling point of 131-134 °C/2 mmHg in a yield of 125.5 g (75% yield) as a colorless solid. Elemental analysis (calculated value C10H9BrO): C, 53.36; H, 4.03. measured value: C, 53.19; H, 3.98. 1H NMR (300 MHz, CDCl3) δ: 7.76 (d, J = 7.6 Hz, 1H, 7-H), 7.71 (d, J = 7.6 Hz, 1H, 5-H), 7.28 (t, J = 7.6 Hz, 1H, 5-H), 7.28 (t, J = 7.6 Hz, 1H, 5-H). 7.6 Hz, 1H, 6-H), 3.36 (dd, J = 17.5 Hz, J = 7.6 Hz, 1H, 3-H), 2.70-2.82 (m, 1H, 2-H), 2.67 (dd, J = 17.5 Hz, J = 3.8 Hz, 1H, 3'-H), 1.34 (d, J = 7.3 Hz, 3H, 2-Me).13C NMR (75 MHz, CDCl3) δ: 208.3, 152.9, 138.2, 137.2, 129.0, 122.6, 122.0, 41.8, 35.7, 16.0.
