Organocatalytic Stereospecific Appel Reaction
Jan Tönjes, Lukas Kell, Thomas Werner*
*Department of Chemistry and Center for Sustainable Systems Design (CSSD), Paderborn University, Warburger Str. 100, 33098 Paderborn, Germany, Email: th.werner
uni-paderborn.de
J. Tönjes, L. Kell, T. Werner, Org. Lett., 2023, 25, 9114-9118.
DOI: 10.1021/acs.orglett.3c03463
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Abstract
A catalytic Appel reaction using a P(III)/P(V) redox cycling at very low catalyst loadings, hexachloroacetone as the halogen source and phenylsilane as the terminal reductant converted alcohols and epoxides containing a wide variety of functional groups to the respective chlorides and dichlorides in very good yields and with high enantiospecificities for inversion.
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proposed mechanism
Protocols for the Synthesis of Chlorinated Products
Conversion of alcohols: Under an argon atmosphere the catalyst (1.7 mg, 10 µmol, 1.0 mol%) was added as a solution in toluene (2.0 M, 0.50 mL) to the alcohol (1.00 mmol, 1.00 equiv). Hexachloroacetone (185 mg, 0.700 mmol, 0.700 equiv) and phenylsilane (108 mg, 1.00 mmol, 1.00 equiv) were added and the reaction mixture was heated to 100 °C in an oil bath for 24 h. After cooling to room temperature, the crude product was purified by column chromatography (eluent pentane:Et2O). The er of the product was determined by GC on a chiral stationary phase for enantioenriched substrates.
Conversion of epoxides: Under an argon atmosphere the catalyst (3.5 mg, 20 µmol, 2.0 mol%) was added as a solution in toluene (1.0 M, 1.0 mL) to the epoxide (1.00 mmol, 1.00 equiv). Hexachloroacetone (370 mg, 1.40 mmol, 1.40 equiv) and phenylsilane (162 mg, 1.50 mmol, 1.50 equiv) were added and the reaction mixture was heated to 100 °C in an oil bath for 24 h. After cooling to room temperature, the crude product was purified by column chromatography (eluent pentane:Et2O). The er of the product was determined by GC or HPLC on a chiral stationary phase for enantioenriched substrates.
Organocatalytic Chlorination of Alcohols by P(III)/P(V) Redox Cycling
L. Longwitz, S. Jopp, T. Werner, J. Org. Chem., 2019, 84, 7863-7870.
Key Words
Apple reaction, alkyl chlorides, 1,2-dichlorides, organocatalysis
ID: J54-Y2023
