Scalable Synthesis of a Chiral Selenium π-Acid Catalyst and Its Use in Enantioselective Iminolactonization of β,γ-Unsaturated Amides

Published as part of the Cluster Organosulfur and Organoselenium Compounds in Catalysis

Abstract

Chiral selenium π-acid catalysis has for a long time been lagging behind other areas of asymmetric catalysis due to a lack of highly enantioselective catalysts. In this regard, we recently developed the first chiral selenium π-acid catalyst which performs the oxidative cyclization of β,γ-unsaturated carboxylic acids with high enantioselectivities. We report herein our improved synthesis of this chiral selenium catalyst, which allows access to a large quantity of the catalyst as the diselenide. In addition, the catalyst is tested in the oxidative cyclization of N-methoxy β,γ-unsaturated amides to give iminolactones with high enantioselectivities.

Key words

selenium - diselenide - asymmetric catalysis - oxidative cyclization - iminolactones

• References and Notes

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• 19 (R,Z)-5-Benzylfuran-2(5H)-one O-Methyl Oxime (8a) Prepared according to the general procedure with 7a (0.10 mmol, 20.5 mg) to give 8a in 73% yield (73 μmol, 14.8 mg) and 97% ee as a colorless oil. [α]_D 18 °C = –204 (c 1.6, CHCl₃); ¹H NMR (396 MHz, CDCl₃): δ = 7.19–7.34 (m, 5 H), 6.56 (dd, J = 6.0, 1.9 Hz, 1 H), 6.09 (dd, J = 6.0, 1.9 Hz, 1 H), 5.39–5.44 (m, 1 H), 3.87 (s, 3 H), 3.26 (dd, J = 13.5, 5.6 Hz, 1 H), 2.89 (dd, J = 13.5, 8.2 Hz, 1 H); ¹³C NMR (100 MHz, CDCl₃): δ = 160.62, 141.59, 135.34, 129.37, 128.67, 127.03, 121.21, 89.42, 62.49, 40.72; HRMS (ESI): m/z [M + Na]⁺ calcd for C₁₂H₁₃NNaO₂: 226.0838; found: 226.0823; HPLC: Daicel CHIRALPAK IC-3, hexane/iPrOH = 5:1, flow rate = 1.0 mL/min, t _R = 10.8 min (major), 14.9 min (minor).
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