Enantioselective Desymmetrization of 3-Substituted Oxetanes: An Efficient Access to Chiral 3,4-Dihydro-2H-1,4-benzoxazines
Viraj A. Bhosale, Martin Nigríni, Martin Dračínský, Ivana Císařová and Jan Veselý*
*Department of Organic Chemistry, Faculty of Science, Charles University, Hlavova 2030, 128 43 Prague, Czech Republic, Email: jan.veselynatur.cuni.cz
V. A. Bhosale, M. Nigríni, M. Dračínský, I. Císařová, J. Veselý, Org. Lett., 2021, 23, 9376-9381.
DOI: 10.1021/acs.orglett.1c03419 (free Supporting Information)
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A chiral phosphoric acid (CPA) catalyzes a versatile transition metal/oxidant free synthesis of chiral 2H-1,4-benzoxazines through enantioselective desymmetrization of prochiral oxetanes (30 examples) in very good yield and high enantioselectivity under mild reaction conditions.
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Organocatalytic Openings of Oxetanes to Dihydro-2H-1,4-Benzoxazines
An oven-dried 4 mL vial was charged with corresponding oxetane (0.05 mmol) and toluene (0.5mL, c= 0.1 M), then organocatalyst (5 mol %, 0.0025 mmol) was added. Then the reaction was stirred at room temperature. Upon completion of the reaction, the resulting mixture was directly subjected to flash column chromatography.