Enantioselective pinacol coupling of aryl aldehydes catalyzed by chiral Salan-Mo(IV) complexes.
Reported herein is the asymmetric pinacol coupling of aromatic aldehydes with chiral Salan-Mo(VI) dioxo complex as an effective precatalyst. Chiral diols were obtained with high diastereoselectivity and enantioselectivity up to 92/8 and 95%, respectively. The possible mechanism of the pinacol coupling reaction with the catalytic system was investigated. The X-ray crystal structure of the precatalyst Mo(L3)O2 was determined and the oxidation state of the intermediate C was confirmed as +4 with X-ray photoelectron spectroscopy study. The proposed mechanism speculated the stereochemical outcome of the reaction, and a working model for the radical coupling of E was proposed, which explained the absolute configuration of the favored (S,S)-enantiomer of the dl isomer.
State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, China.
Hongwei
H
Yang
Hongsong
H
Wang
Chengjian
C
Zhu
D000438:Alcohols / Q000138:chemical synthesis* / Q000737:chemistry; D001547:Benzaldehydes / Q000737:chemistry*; D002384:Catalysis; D018360:Crystallography, X-Ray; D005026:Ethylene Glycols / Q000737:chemistry*; D008024:Ligands; D008958:Models, Molecular; D015394:Molecular Structure; D008982:Molybdenum / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D013237:Stereoisomerism
D000438:Alcohols; D001547:Benzaldehydes; D005026:Ethylene Glycols; D008024:Ligands; D009942:Organometallic Compounds; D008982:Molybdenum