Ammonium Chloride → 2-Ethenylbicyclo[4.2.0]octa-1,3,5-triene

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Reaction Steps

To a 500 mL round bottom neck flask was added methyltriphenylphosphonium bromide 1.1 (48.6 g, 136.2 mmol), 220 mL of anhydrous THF, and the solution was cooled to −78 C. n-BuLi (2.5 M in hexane, 52.8 mL, 132 mmol) was added dropwise, and the reaction mixture was allowed to warm to room temperature. The yellow-orange solution was cooled to −78 C, and the aldehyde 1.2 (14.32 g, 108.4 mmol), diluted in anhydrous THF (70 mL) added slowly. The mixture was warmed to room temperature and stirring continued for 2 h. The reaction was treated sequentially with saturated NH4Cl and saturated NaHCO3 solution and the crude product was filtered over Celite, washed with diethyl ether/hexane (1:1), and evaporated to dryness (no heat) to give the crude product. Further purification by column chromatography using 5% diethyl ether/hexane as eluting solvents followed by vacuum distillation (75 C, 1.0 mm) gave the pure 4-Vinylbenzocyclobutene 1.3 as a colorless liquid (11 g, 78%). 1H NMR (300 MHz, CDCl3): δ 7.26 (d, 1H), 7.20 (s, 1H), 7.04 (d, 1H), 6.74 (dd, 1H), 5.70 (d, 1H), 5.20 (d, 1H), 3.19 (s, 4H).

Provenance & Evidence