Deaminative Addition of Alkylpyridinium Salt to Aldehyde
Yu Huang, Zhengqiang Liu and Wenbo H. Liu*
*School of Chemistry, Sun Yat-sen University, Guangzhou 510006, China, Email: liuwb29mail.sysu.edu.cn
Y. Huang, Z. Liu, W. H. Liu, Org. Lett., 2023, 25, 4934-4939.
DOI: 10.1021/acs.orglett.3c01724
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Abstract
CrCl2 mediates a nucleophilic addition of a primary amine derivative to an aldehyde to provide an alcohol. This radical-polar crossover process is selective for aldehydes and compatible with numerous functional groups, which are not tolerated under classical Grignard-type conditions.
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proposed mechanism
Example Procedure
[1,1’-Biphenyl]-4-carbaldehyde (36.4 mg, 0.2 mmol, 1.0 equiv), pyridinium salt 2a (191.8 mg, 0.4 mmol, 2.0 equiv), and B2Pin2 (50.8 mg, 0.2 mmol, 1.0 equiv) were added to an oven-dried 10 mL Schlenk tube with a magnetic bar. The tube was evacuated and refilled with Ar for three times. DMF (2.0 mL) was added and CrCl2 (61.5 mg, 0.5 mmol, 2.5 equiv) was added. The reaction mixture was stirred in a 90 °C oil bath for 24 h. When the reaction solution was cooled to room temperature, the solution was poured into water (10.0 mL) to quench the reaction and the mixture was extracted with EtOAc (3 × 5.0 mL). The combined organic layers were washed with brine, dried over anhydrous Na2SO4, filtered, and concentrated under reduced pressure. The residue was purified by column chromatography on silica gel to afford 3a as a white solid.
Rf = 0.5 (eluent: petroleum ether/EtOAc = 10:1). Yield: 48.0 mg (89%).
Key Words
alcohols, bis(pinacolato)diboron
ID: J54-Y2023