3.4. General Procedure D—Wittig Reaction

Methyltriphenylphosphonium bromide (1.287 g, 3.601 mmol) was suspended in 15 mL of dry THF at 0 °C. KOtBu (0.404 g, 3.601 mmol) was added to the suspension and a bright yellow color was observed. The mixture was stirred at 0 °C for 30 min. Then 5-chloro-2,3-dihydro-1H-inden-1-one (0.200 g, 1.200 mmol) was added neat and the reaction mixture was stirred at 0 °C to r.t. for 4 h (the solution turned green and then dark brown). Water was added to the mixture and the product was extracted with CH₂Cl₂ and dried with Na₂SO₄, filtrated and concentrated in vacuum. The residue was purified by column chromatography using n-hexane. Adapted from Liwosz and Chemler [24].

5-chloro-1-methylene-2,3-dihydro-1H-indene (7): Incolor oil. 83% yield. HPLC: 9.720 min (99.4%). ¹H-NMR (200 MHz, CDCl₃) δ in ppm: 2.77–2.85 (m, 2H), 2.93–3.00 (m, 2H), 5.04–5.07 (t, 1H), 5.42–5.44 (t, 1H), 7.15–7.19 (d, J = 8.0 Hz, 1H), 7.23 (s, 1H), 7.38–7.42 (d, J = 8.0 Hz, 1H); ¹³C-NMR (50 MHz, CDCl₃) δ in ppm: 13.1, 37.6, 119.7, 124.1, 126.3, 129.2, 130.7, 139.5, 144.8, 146.1.