Compound (R,(Z,M),(E,P))-5

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InChIKey DISCPVKFHDBAMP-FVOCXXNYSA-N

Synthetic procedure: See article for the definitive version of this procedure and for full experimental details.

A solution of 2-fluoro-2,4,7-trimethyl-1H-indene-1,3(2H)-dione S2 (402 mg, 1.9 mmol), P₄S₁₀ (2.16 g, 9.7 mmol) and Lawesson’s reagent (3.14 g, 7.76 mmol) in toluene (25 mL) was heated at reflux under a nitrogen atmosphere until full conversion to the bisthioketone as monitored by ¹⁹F NMR (~16 h; ¹⁹F NMR (376 MHz, CDCl₃): δ (ppm) −134.5 (q, J = 20.6 Hz)). The mixture was left to cool and passed directly over a short column of silica gel. The column was washed (pentane : ethyl acetate – 10 : 1) until no more thioketone was eluted as indicated by TLC. The solvents were removed under reduced pressure. The resulting red colored oil was redissolved in toluene (10 mL) and slowly added into a stirred solution of freshly prepared 9-diazo-2-methoxy-9H-fluorene (559 mg, 2.5 mmol) (prepared according to: Pollard, M. M., Meetsma, A. & Feringa, B. L. A redesign of light-driven rotary molecular motors. Org. Biomol. Chem. 6, 507–512 (2008)) in THF (40 mL). After stirring at room temperature for 3 h, hexamethylphosphanetriamine (460 μl, 2.5 mmol) was added and the stirring continued overnight. The volatiles were evaporated under reduced pressure. Absolute ethanol (30 mL) was added to the residue and the mixture was stirred for 30 min. The yellow precipitate was filtered off and washed with ethanol (3 × 10 mL) to give 9,9'-(2-fluoro-2,4,7-trimethyl-1H-indene-1,3(2H)-diylidene)bis(2-methoxy-9H-fluorene) 5 as a mixture of isomers (1:1:2 by NMR) inseparable by column chromatography as a bright yellow solid (322 mg, 34%). M.p. 240.5–241.4 °C (decomp.); ¹H NMR (400 MHz, CDCl₃): δ (ppm) 8.06 (dd, J₁ = 6.5 Hz, J₂ = 6.5 Hz, 2H), 7.66 (m, 2H), 7.60 (dd, J₁ = 8.6 Hz, J₂ = 8.6 Hz, 8H), 7.44 (d, J = 7.9 Hz, 2H), 7.24−7.32 (m, 10H), 7.03–7.08 (m, 4H), 6.92 (dd, J₁ = 8.4 Hz, J₂ = 1.1 Hz, 2H), 6.87 (dd, J₁ = 8.2 Hz, J₂ = 2.0 Hz, 2H), 3.93 (s, 6H), 3.69 (s, 3H), 3.67 (s, 3H), 2.17−2.25 (m, 18H); ¹³C NMR (100 MHz, CDCl₃): δ (ppm) 159.99, 159.60, 159.58, 146.39, 146.37, 146.3, 146.19, 146.18, 146.1, 142.3, 142.21, 142.19, 142.15, 142.13, 142.07, 141.14, 141.12, 141.00, 140.95, 140.67, 140.64, 139.42, 139.36, 139.33, 139.30, 137.74, 135.52, 135.50, 135.43, 135.41, 135.34, 135.32, 135.22, 135.20, 134.32, 134.30, 133.95, 133.54, 133.40, 133.26, 132.35, 132.32, 132.30, 132.27, 128.75, 128.31, 127.85, 127.81, 127.71, 127.67, 126.34, 126.29, 126.20, 126.18, 126.13, 126.11, 124.09, 124.06, 120.39, 120.36, 119.13, 119.01, 114.49, 114.35, 114.07, 114.00, 113.92, 113.86, 113.43, 111.07, 111.00, 110.24, 109.88, 109.01, 108.94, 56.14, 56.01, 55.90, 55.79, 22.58, 22.34, 21.65, 21.62; ¹⁹F NMR (376 MHz, CDCl₃): δ (ppm) −132.7 (qt, J₁ = 16.9 Hz, J₂ = 4.8 Hz), −133.1 (qt, J₁ = 16.9 Hz, J₂ = 5.2 Hz), −133.3 (qt, J₁ = 16.8 Hz, J₂ = 5.4 Hz); HRMS (APCI-Ion trap): calcd for C₄₀H₃₂FO₂⁺ [M + H]⁺ 563.2381 found 563.2364.

A solution of 5 was subjected to SFC (Chiralpak^®IA, 32% 2-propanol, 340 nm, 3.5 mLmin⁻¹, T = 40 °C, 180 bar) t_R = 6.3 min. The collected solution was concentrated in vacuo and the residue was subjected to column chromatography on silica gel (pentane : CH₂Cl₂ – 5 : 1) affording (R,(Z,M),(E,P))-5. ¹H NMR (599 MHz, CD₂Cl₂) δ = 8.04 (t, J = 6.5 Hz, 1H), 7.64 (dd, J₁ = 4.9 Hz, J₂ = 2.2 Hz, 1H), 7.60 (d, J = 8.2 Hz, 2H), 7.58 (d, J = 8.1 Hz, 2H), 7.43 (d, J = 7.9 Hz, 1H), 7.33 – 7.22 (m, 5H), 7.05 – 7.03 (m, 2H), 6.91 (dd, J₁ = 8.3 Hz, J₂ = 2.1 Hz, 1H), 6.85 (dd, J₁ = 8.2 Hz, J₂ = 2.3 Hz, 1H), 3.91 (s, 3H), 3.68 (s, 3H), 2.23 (s, 3H), 2.18 (d, J =17.1 Hz, 3H), 2.18 (s, 3H).