New sterically-hindered 6th-substituted 3,5-di-tert-butylcatechols/o-quinones with additional functional groups and their triphenylantimony(V) catecholates

Abstract

The functionalization of 3,5-di-tert-butylcatechol with a group CH2X in the 6th position (where the group X has the additional heteroatoms) was performed in order to prepare new functionalized 3,5-di-tert-butylcatechols of the common type (6-(CH2-X)-3,5-Cat)H2, where X is methoxy group (catechol 1a, X = OMe), 3,5-dimethylpyrazol-1-yl (catechol 1b, X = Me2Pyr) and benzimidazol-1-yl (catechol 1c, X = Benzimid). The oxidation of catechols 1a-1c with K3[Fe(CN)6] in alkaline medium leads to new functionalized o-quinones 2a-2c and corresponding o-benzoquinones of the type 6-(CH2-X)-3,5-Q. The molecular structures of pyrazolyl-containing catechol 1b and its o-quinone 2b in crystal were determined by single-crystal X-ray analysis. The treatment of o-benzoquinones with triphenylstibine gives new triphenylantimony(V) catecholates (6-(CH2-X)-3,5-Cat)SbPh3 (3a-3c) containing additional functional groups in the substituent at the 6th position of catecholato aromatic ring. The molecular structures of catecholates (6-(CH2-OMe)-3,5-Cat)SbPh3 (3a) and (6-(CH2-Me2Pyr)-3,5-Cat)SbPh3·H2O (3b·H2O) in crystal were determined by means of single-crystal X-ray analysis. In crystal, complex 3a forms two geometrical isomers with different position of CH2OMe group towards aromatic cycle of catecholato ligand. The “CPh–H…π-system” interactions between these isomers were found. The coordination environment of the central antimony atom in 3b·H2O is a distorted octahedral with a coordinated water molecule which is involved in the intramolecular hydrogen bonding with pyrazolyl group of catecholato ligand.