Efficient recycling of fluorous versions of highly enantioselective S, N-chelated zinc aminoarene thiolate catalysts for the 1,2-addition of diethylzinc to benzaldehydes

• Published in: Journal of molecular catalysis. A, Chemical Chemical, 2008-05, Vol.287 (1), p.65-69
• Main Authors: Kleijn, Henk, Jastrzebski, Johann T.B.H., Deelman, Berth-Jan, van Koten, Gerard
• Format: Article
• Language: English
• Subjects: 1,2-Addition; Benzaldehyde; Catalysis; Chemistry; Diethylzinc; Enantioselective; Exact sciences and technology; Fluorous biphase separation; General and physical chemistry; Partition coefficient; S,N-chelating aminoarene thiolate ligand; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
• ISSN: 1381-1169; 1873-314X
• DOI: 10.1016/j.molcata.2008.02.018

New enantiomerically pure S, N-chelated ( R)-Zn(Et)SR complexes, 3a– 3c (R = 2-[CHMeN(CH 2) 4]-5-[SiMe 3− n (CH 2CH 2C x F 2 x+1 ) n ]C 6H 3; n = 1, x = 10; n = 2, 3 and x = 8), have been synthesized from the reaction of EtZnCl and the corresponding trimethylsilyl(aminoaryl) thioethers, or lithium aminoarene thiolate 2c. Complexes 3a– 3c were successfully used as highly enantioselective catalysts for the 1,2-addition ( e.e. up to 92%) of diethylzinc to benzaldehyde in perfluoromethylcyclohexane/ n-octane. At 2.5 mol%, catalyst 3c, thanks to its three CH 2CH 2C 8F 17 tails, could be reused at least 10 times with retention of its initial high enantioselectivity, thereby significantly increasing the turnover number per unit amount of catalyst in comparison with earlier studies.