3.1. General Procedure A—Corey-Chaykovsky Epoxidation

4.0 eq. of NaH (60% dispersion in mineral oil) was placed in a three-necked flask under argon and then DMSO (0.6 M) and the ketone were added, after which 2.25 eq. of trimethylsulfonium iodide was also added, all at once. The reaction mixture was stirred at ambient temperature. After controlling through TLC, the mixture was poured over ice and extracted with diethyl ether and ethyl acetate (1:1). The extracts were combined, washed with brine and afterwards dried over Na₂SO₄. The solvent was removed under vacuum, and the residue was used without purification for the next step. Adapted from Winter [19].

2-bromo-6,7,8,9-tetrahydrospiro[benzo[7]annulene-5,2′-oxirane] (2a): Yellow oil. 95% yield. ¹H-NMR (200 MHz, CDCl₃) δ in ppm: 1.62–1.80 (m, 2H), 1.80–2.15 (m, 2H), 2.74 (d, 1H, J = 6.0 Hz), 2.82–2.87 (m, 2H), 2.98 (d, 1H, J = 6.0 Hz), 7.30 (m, 3H); ¹³C-NMR (50 MHz, CDCl₃) δ in ppm: 27.0, 28.6, 35.9, 36.0, 53.9, 60.8, 121.2, 126.9, 129.1, 131.8, 140.1, 143.3.

6-bromo-3,4-dihydro-2H-spiro[naphthalene-1,2′-oxirane] (2b): Yellow solid. 90% yield. ¹H-NMR (200 MHz, CDCl₃) δ in ppm: 1.75–1.85 (m, 2H), 2.06–2.11 (m, 2H), 2.83–2.87 (m, 2H), 2.97 (s, 2H), 6.92–6.96 (d, 2H), 7.27–7.29 (s, 1H); ¹³C-NMR (50 MHz, CDCl₃) δ in ppm: 21.9, 29.6, 31.7, 56.4, 58.9, 121.5, 125.4, 129.6, 131.4, 134.9, 141.7.

2-(4-bromophenyl)-2-methyloxirane (2c): Yellow solid. 90% yield. ¹H-NMR (200 MHz, CDCl₃) δ in ppm: 1.70 (s, 3H), 2.74–2.77 (d, 1H), 2.97–2.99 (d, 1H), 7.22–7.26 (d, J = 8.0 Hz, 2H), 7.44–7.48 (d, J = 8.0 Hz, 2H); ¹³C-NMR (50 MHz, CDCl₃) δ in ppm: 21.7, 56.5, 57.1, 121.6, 127.2, 131.6, 140.4.