Controlled oxidation of organic sulfides to sulfoxides under ambient conditions by a series of titanium isopropoxide complexes using environmentally benign H2O2 as an oxidant.
Controlled oxidation of organic sulfides to sulfoxides under ambient conditions has been achieved by a series of titanium isopropoxide complexes that use environmentally benign H(2)O(2) as a primary oxidant. Specifically, the [N,N'-bis(2-oxo-3-R(1)-5-R(2)-phenylmethyl)-N,N'-bis(methylene-R(3))-ethylenediamine]Ti(O(i)Pr)(2) [R(1) = t-Bu, R(2) = Me, R(3) = C(7)H(5)O(2) (1b); R(1) = R(2) = t-Bu, R(3) = C(7)H(5)O(2) (2b); R(1) = R(2) = Cl, R(3) = C(7)H(5)O(2) (3b) and R(1) = R(2) = Cl, R(3) = C(6)H(5) (4b)] complexes efficiently catalyzed the sulfoxidation reactions of organic sulfides to sulfoxides at room temperature within 30 min of the reaction time using aqueous H(2)O(2) as an oxidant. A mechanistic pathway, modeled using density functional theory for a representative thioanisole substrate catalyzed by 4b, suggested that the reaction proceeds via a titanium peroxo intermediate 4c', which displays an activation barrier of 22.5 kcal mol(-1) (DeltaG(++)) for the overall catalytic cycle in undergoing an attack by the S atom of the thioanisole substrate at its sigma*-orbital of the peroxo moiety. The formation of the titanium peroxo intermediate was experimentally corroborated by a mild ionization atmospheric pressure chemical ionization (APCI) mass spectrometric technique.
Panda
Manas K
MK
Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400 076.
Shaikh
Mobin M
MM
Ghosh
Prasenjit
P
D018360:Crystallography, X-Ray; D006861:Hydrogen Peroxide / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D016877:Oxidants / Q000737:chemistry*; D010084:Oxidation-Reduction; D013237:Stereoisomerism; D013438:Sulfhydryl Compounds / Q000737:chemistry*
D009942:Organometallic Compounds; D016877:Oxidants; D013438:Sulfhydryl Compounds; C102815:titanium isopropoxide; D006861:Hydrogen Peroxide