Palladium-based Kinetic Resolution of Racemic Tosylaziridines

Abstract

Dicationic Pd(II) complexes with chiral pyridine bis(oxazoline) ligands are catalysts for kinetic resolution of racemic styrene tosylazirdines. Treatment of styrene tosylaziridine with 0.5 equivalents of alcohol in the presence of the chiral Pd catalyst affords β-alkoxy tosylamide with ee up to 71%.

Key words

palladium - kinetic resolution - aziridine - asymmetric - alcoholysis

References

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11

Typical procedure for Pd-catalyzed alcoholysis of styrene tosylaziridine: To a mixture of aziridine (50 mg, 0.18 mmol) and S-1 (12 mg, 0.018 mmol) in CH₂Cl₂ (1 mL) was added dried MeOH (4 µL, 0.09 mmol) under nitrogen at 0 °C. The mixture was stirred at that temperature for 1-5 h and purified by flash chromatography (silica gel, 50% ether-hexane). Spectroscopic data for PhCH(OMe)CH₂NHTs: ¹H NMR (400 MHz, acetone-d ₆): δ 7.90 (d, J = 8.0 Hz, 2 H), 7.53 (d, J = 8.0 Hz, 2 H), 7.45 (m, 5 H), 6.65 (s, br, 1 H), 4.35 (dd,
J = 8.8, 4.4 Hz, 1 H), 3.20 (m, 2 H), 3.25 (s, 3 H), 2.56 (s,
3 H); ¹³C NMR (100 MHz, acetone-d ₆): δ 143.5, 140.0, 139.0, 130.1, 129.1, 128.7, 127.6, 127.3, 83.0, 56.8, 50.2, 21.3; MS (+CI) m/z (relative intensity): 306 (M + H⁺, 18), 274 (M - OMe⁺, 100). Anal. Calc. for C₁₆H₁₉NOS₃ (305.39): C, 62.93; H, 6.27; N, 4.59. Found: C, 62.91; H, 6.35; N, 4.54.

15

Leung, W.-H.; Chan, E. Y. Y.; Wong, W.-T., unpublished results.

17

Initial rates of reactions were estimated by monitoring the concentration of aziridine using GLC.