Aerobic oxidative meso-diols

Subsequent to the development of the (salen)Cr-catalyzed desymmetrization of meso-epoxides with azide (Scheme 7.3), Jacobsen discovered that the analogous (salen)Co(n) complex 6 promoted the enantioselective addition of benzoic acids to meso-epoxides to afford valuable monoprotected C2-symmetric diols (Scheme 7.15) [26], Under the reaction conditions, complex 6 served as a precatalyst for the (salen) Co(iii)-OBz complex, which was fonned in situ by aerobic oxidation. While the enantioselectivity was moderate for certain substrates, the high crystallinity of the products allowed access to enantiopure materials by simple recrystallization. 

Shimizu, H., Onitsuka, S., Egami, H., et al. (2005). Ruthenium(Salen)-Catalyzed Aerobic Oxidative Desymmetrization of Meso-Diols and its Kinetics, J. Am. Chem. Soc., 127, pp. 5396-5413. 

Aerobic Alcohol Oxidations. The combination of PdCl2(CH3CN)2 (5-10 mol%) with (—(-sparteine (20 mol%) constitutes an effective catalyst system for the oxidative kinetic resolution of secondary alcohols with molecular oxygen as the terminal oxidant, with enantiomeric excesses t)q)ically above 90% ee (eq 45). This enantioselective aerobic oxidation has been successfully extended to the desymmetrization of meso-1,3-diols. 

Chiral N-sulfonyldiamine ligands are used to create effective chiral bifunctional amidoiridium catalysts for the asymmetric aerobic oxidation of meso- and prochiral diols to give up to >99% ee of hydroxyl ketones and 50%ee oflactones. " These catalysts can be also applied for an efficient oxidative kinetic resolution of racemic secondary alcohols affording R enantiomers with >99% ee and with 46—50% yields. 

Suzuki T, Morita K, Matsuo Y, Hiroi K. Catalytic asymmetric oxidative lactonizations of meso-diols using a chiral iridium complex. Tetrahedron Lett. 2003 44 2003—2006. Moritani J, Hasegawa Y, Kayaki Y, Ikariya T. Aerobic oxidative desymmetrization of meso-diols with bifunctional amidoiridium catalysts bearing chiral N-sulfonyldiamine ligands. Tetrahedron Lett. 2014 55 1188-1191. 

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