Facile and efficient synthesis of C-hydroxycarboranes and C,C'-dihydroxycarboranes.
C-Hydroxylated carboranes, carboranols, have interesting properties resulting from their hydroxyl protons being highly acidic because of the electron-deficient nature of the carborane cage. We described here an efficient synthesis of C-hydroxycarboranes 2 and C,C'-dihydroxycarboranes 3 by the reaction of carboranyl lithium and trimethylborate, followed by oxidation with hydrogen peroxide in the presence of acetic acid, to afford the corresponding o-, m-, and p-hydroxycarboranes 2 and o-, m-, and p-dihydroxycarboranes 3 selectively in high yields through a one-pot procedure. The m- and p-carborane isomers of 2 and 3 were obtained in especially good yields (2b, 85%; 2c, 85%; 3b, 95%; 3c, 96%). DFT calculations were performed on the dihydroxycarboranes 3 to compare the geometrical features of the isomers at the same level of theory and to characterize their electronic and NMR spectroscopic (13C chemical shift) properties.
Ohta
Kiminori
K
Faculty of Pharmaceutical Sciences, Tohoku Pharmaceutical University, 4-4-1 Komatsushima, Aoba-ku, Sendai 981-8558, Japan.
Goto
Tokuhito
T
Yamazaki
Hiroto
H
Pichierri
Fabio
F
Endo
Yasuyuki
Y
D001880:Boranes / Q000737:chemistry*; D001896:Boron Compounds / Q000737:chemistry*; D006900:Hydroxylation; D007202:Indicators and Reagents; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D008958:Models, Molecular; D015233:Models, Statistical; D010084:Oxidation-Reduction
D001880:Boranes; D001896:Boron Compounds; D007202:Indicators and Reagents