Dynamic catalytic asymmetric

Chirality transfer in catalytic asymmetric hydrogenation can be achieved not only by using powerful chiral ligands such as BINAP or DuPhos but also by the formation of a dynamic conformational isomer. The availability of many enantiomerically pure diols allows the production of electron-deficient, bi-dentate phosphate in the form of 27. The backbone O-R -O can define the chirality of the 0-R2-0 in complex 28, hence realizing the chirality transfer.44... 

A dynamic kinetic resolution has been employed to achieve a catalytic asymmetric reductive amination of aldehydes.332 Reductive amination of ketones and aldehydes by sodium triacetoxyborohydride has been reviewed, highlighting its advantage over other reagents.333... 

Hoffmann S, Nicoletti M, List B (2006) Catalytic asymmetric reductive ami-nation of aldehydes via dynamic kinetic resolution. J Am Chem Soc 128 13074-13075... 

Notz W, Tanaka F, Watanabe S, Chaudari NS, Turner JM, Thayumanavan R, Barbas CF 3rd (2003) The direct organocatalytic asymmetric mannich reaction unmodified aldehydes as nucleophiles. J Org Chem 68 9624-9634 Noyori R (2002) Asymmetric catalysis science and opportunities (Nobel lecture). Angew Chem Int Ed Engl 41 2008-2022 Noyori R, Tokunaga M, Kitamura M (1995) Stereoselective organic synthesis via dynamic kinetic resolution. Bull Chem Soc Jpn 68 36-55 Ohkuma T, Kitamura M, Noyori R (2000) Asymmetric hydrogenation. In Ojima I (ed) Catalytic asymmetric synthesis, 2nd edn. Wiley-VCH, New York, p 1-110... 

Hermitage S, Howard JAK, Jay D, Pritchard RG, Probert MR, Whiting A (2004) Mechanistic studies on the formal aza-Diels-Alder reactions of N-aryl imines evidence for the non-concertedness under Lewis-acid catalysed conditions. Org Biomol Chem 2 2451-2460 Hoffmann S, Nicoletti M, List B (2006) Catalytic asymmetric reductive ami-nation of aldehydes via dynamic kinetic resolution. J Am Chem Soc 128 13074-13075... 

S. Y. Tosaki, R. Tsuji, T. Ohshima, M. Shibasaki, Dynamic ligand exchange of the lanthanide complex leading to structural and functional transformation One-pot sequential catalytic asymmetric epoxidation-regioselective epoxide-opening process, J. Am. Chem. Soc. 127 (2005) 2147. 

Despite the number of reports of the asymmetric synthesis of tertiary a-aryl cyclohexanones, there have only been three reports which describe the asymmetric synthesis of tertiary a-aryl cyclopentanones. The first of these was reported by Shi via asymmetric epoxidation of benzylidene cyclobutanes and epoxide rearrangement in a subsequent step [76]. Backvall used a dynamic kinetic resolution of aUyhc alcohols-aUylic substitution-oxidative cleavage sequence to access 2-phenylcyclopentanone [77]. The first direct catalytic asymmetric synthesis of tertiary a-aryl ketones was recently described by Kingsbury using a series of Sc-catalysed diazoalkane-carbonyl homologations with bis/tris oxazohne ligands [78]. 

Toste s group made several modifications of bis(HBHC)-digold complex 40 by placing differently substituted aryl groups at the binaphthyl 3,3 -positions of the diamine synthon and examined them in catalytic dynamic kinetic asymmetric transformations of propargyl esters (Scheme 16.14) [29b]. Drastic substituent effects on enantioselectivity were observed, with j -trifluoromethylphenyl-... 

S. Lin, L. Deiana, G. Zhao, A. Cordova, J. Sun, Angew. Chem. Int. Ed 2011, 50, 7624-7630. Dynamic one-pot three-component catalytic asymmetric transformation hy comhination of hydrogen-bond-donating and amine catalysts. 

Wang J, Feringa BL (2011) Dynamic control of chiral space in a catalytic asymmetric reaction using a molecular motor. Science 331 1429-1432... 

Scheme 2.25 Dynamic one-pot, three-component catalytic asymmetric cycloaddition.

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