Functional Group Oxidation
In a remarkable example of chemoselective oxidation, Scott J. Miller at Yale identified (Nature Chem. 2012, 4, 990. ) a peptide catalyst that selectively epoxidized the 6,7-olefin of farnesol 1. Phil S. Baran at Scripps-La Jolla developed (Nature Chem. 2012, 4, 629. ) the Tz° sulfonate as a "portable desaturase" capable of site-specific C-H functionalization of complex molecules, such as in the conversion of peptide 3 to 4.
A unique method for the preparation of α-oxygenated ketones was developed (Angew. Chem. Int. Ed. 2012, 51, 7799. ) by Laura L. Anderson at the University of Illinois at Chicago. Cross-coupling of cyclohexenyl boronic acid with N-hydroxyphthalimide produced N-enoxyphthalimides 5, which underwent a trihetero [3,3]-sigmatropic rearrangement to produce, after hydrolysis and protection, ketone 6.
The enantioselective α-hydroxylation of oxindole 7 with atmospheric O2 catalyzed by pentanidium 8 was reported (Org. Lett. 2012, 14, 4762. ) by Zhiyong Jiang at Henan University and Choon-Hong Tan at Nanyang Technological University. A catalytic Baeyer-Villiger oxidation of ketones such as 10 using highly reactive metal borate salts was developed (Angew. Chem. Int. Ed. 2012, 51, 9093. ) by Kazuaki Ishihara at Nagoya University.
Masatoshi Shibuya and Yoshiharu Iwabuchi at Tohoku University found (Org. Lett. 2012, 14, 5010. ) that nitroxyl radicals such as 13 catalyzed the oxidative cleavage of diols to carboxylic acids, such as in the conversion of 12 to 14. A highly reactive iridium catalyst 16 was reported (Angew. Chem. Int. Ed. 2012, 51, 12790. ) by Ken-ichi Fujita and Ryohei Yamaguchi at Kyoto University, which had high turnover numbers under mild conditions for the oxidation of alcohols including 15.
Frank W. Foss Jr at the University of Texas at Arlington developed (Org. Lett. 2012, 14, 5150. ) a biomimetic Dakin oxidation of electron-rich aryl aldehydes such as 18, using the flavin-type catalyst 19, Hantzsch ester, and oxygen as the terminal oxidant. Flavin-catalyzed oxidation of aldehydes using catalyst 22 was also reported (Org. Lett. 2012, 14, 3656. ) by David R. Carbery at the University of Bath.
Carlos F. Barbas III at Scripps-La Jolla developed (Angew. Chem. Int. Ed. 2012, 51, 12538. ) a catalytic conversion of aldehydes such as 24 to the corresponding O-acyl N-hydroxyimides (cf. 25), which could be used for in situ amidations and esterifications. A cooperative catalysis system for the oxidation of benzyl amine 26 to imine 27 using polymer-incarcerated, carbon-stabilized platinum nanoclusters (PI/CB-Pt) and catechol was discovered (J. Am. Chem. Soc. 2012, 134, 13970. ) by Shu Kobayashi at the University of Tokyo. Xuefeng Fu at Peking University found (Org. Lett. 2012, 14, 5692. ) that AIBN readily initiated the oxidative transformation of amines, such as with the α-cyanation of 28. Finally, Thanh Binh Nguyen at the CNRS in France showed (Org. Lett. 2012, 14, 5948. ) that elemental sulfur served as a traceless oxidant for the conversion of amine 30 to benzazole 32.