Compound 23

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

To an oven-dried 8 mL vial equipped with a teflon stir bar was added N-(2,3-dimethylbut-2-en-1-yl)-4-methyl-N-(4-oxobutyl)benzenesulfonamide (0.3 mmol, 1 equiv.). A septum cap was affixed, and the vial was purged with nitrogen followed by the addition of solvent (0.6 mL, 0.5 M). The cap was briefly removed to allow for the addition of powder catalysts – Ir[Fmppy]₂(dtbbpy)PF₆(9 mg, 0.009 mmol, 0.03 equiv.) and the TFA salt of (R)-2-(tert-butyl)-3-methylimidazolidin-4-one (16 mg, 0.06 mmol, 0.20 equiv.). After resealing the vial, (2,4,6)-triisopropylbenzenethiol (15 µL, 0.06 mmol, 0.20 equiv.) and distilled water (5.4 µL, 0.3 mmol, 1 equiv.) were added through the septum cap. The heterogeneous bright yellow solution was cooled to 0 °C and sparged with dried nitrogen for 15 minutes with gentle stirring during which the reaction became homogeneous. The nitrogen line and vent needle were removed, the vial cap was double-sealed with parafilm, and the reaction was cooled to the desired temperature. The stirred solution was irradiated with blue LED light for 24h. Yield obtained by ¹H NMR analysis using benzyl ether as an internal standard. Results: 60% yield, >20:1 dr, 50% ee. Analytical data: ¹H NMR (500 MHz, CDCl₃): δ 9.74 (d, J = 2.5 Hz, 1H), 7.59 (d, J = 8.2 Hz, 2H), 7.31 (d, J = 8.1 Hz, 2H), 3.48-3.46 (m, 1H), 3.01 (d, J = 11.6 Hz, 1H), 2.50 (t, J = 10.5 Hz, 1H), 2.45 (d, J = 11.6 Hz, 1H), 2.42 (s, 3H), 2.37 (ddd, J = 9.7, 4.3, 2.5 Hz, 1H), 2.02-1.93 (m, 2H), 1.74-1.69 (m, 1H), 1.10 (s, 3H), 0.93 (d, J = 4.4 Hz, 3H), 0.91 (d, J = 4.5 Hz, 3H); ¹³C NMR (125 MHz, CDCl₃): δ 204.0, 143.5, 133.0, 129.6, 127.4, 51.9, 51.5, 44.8, 38.7, 33.1, 21.5, 21.4, 17.1, 17.0, 16.6; HRMS (ESI⁺) Calcd. for C₁₇H₂₅NO₃S+H, 324.1628; Found, 324.1633; IR (thin film, cm^-1) 2967, 2879, 1715, 1598, 1466, 1395, 1335, 1268, 1160, 1092, 1007, 942, 915, 815, 733, 655; TLC (98:2 DCM:Et₂O): R_f= 0.55; HPLC analysis of the corresponding alcohol (AD, 20% iPrOH/hexane, 1.0 mL/min, 270 nm) indicates 50% ee: t_R= 9.9, 11.3 min.