Cobalt-Catalyzed Diastereo- and Enantioselective Reductive Allyl Additions to Aldehydes with Allylic Alcohol Derivatives via Allyl Radical Intermediates
Lei Wang, Lifan Wang, Mingxia Li, Qinglei Chong* and Fanke Meng*
*Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, CAS, 345 Lingling Road, Shanghai 200032, China, Email: chongqlsioc.ac.cn, mengfsioc.ac.cn
L. Wang, L. Wang, M. Li, Q. Chong, F. Meng, J. Am. Chem. Soc., 2021, 143, 12755-12765.
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An unprecedented cobalt-catalyzed highly site-, diastereo-, and enantioselective protocol for stereoselective formation of nucleophilic allyl-Co(II) complexes followed by addition to aldehydes provides diversified enantioenriched homoallylic alcohols with a remarkably broad scope of allyl groups that can be introduced.
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Representative Experimental Procedure for Co-Catalyzed Reductive Allyl Addition to Aldehydes with Lewis Acid
In a N2-filled glove-box, an oven-dried vial (8 mL) with a magnetic stir bar was charged with CoI2 (12.5 mg, 0.04 mmol, 10 mol %), ligand (S)-4h (15.3 mg, 0.04 mmol, 10 mol %), Mn (33 mg, 0.6 mmol, 1.5 equiv) and MeCN (2.0 mL). The vial was sealed with a cap (phenolic open top cap with red PTFE/white silicone septum) and the solution was allowed to stir at 23 °C for one hour. The substrate 6a (93.7 mg, 0.4 mmol, 1.0 equiv), 1a (50.9 mg, 0.48 mmol, 1.2 equiv) and La(OTf)3 (23.4 mg, 0.04 mmol, 10 mol %) were added to the solution. The vial was re-sealed with a cap (phenolic open top cap with red PTFE/white silicone septum) and the mixture was allowed to stir at 23 °C for 14 h. Upon completion, the reaction was quenched by 2 mL saturated aqueous solution of NH4Cl and extracted with diethyl ether (3*10 mL). The combined organic layer was washed with brine (10 mL) and dried over Na4SO4. After the solids were filtered off, the solvent was removed under reduced pressure and the residue was purified by silicagel column chromatography (eluent: hexanes/ethyl acetate 10:1) to afford 7a as colorless oil (78.1 mg, 0.35 mmol, 87%).