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Controlled oxidation of organic sulfides to sulfoxides under ambient conditions by a series of titanium isopropoxide complexes using environmentally benign H2O2 as an oxidant.

Dalton transactions (Cambridge, England : 2003) (2010-02-18)
Manas K Panda, Mobin M Shaikh, Prasenjit Ghosh
ABSTRACT

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.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Titanium(IV) isopropoxide, 97%
Sigma-Aldrich
Titanium(IV) isopropoxide, 99.999% trace metals basis
Sigma-Aldrich
Titanium(IV) isopropoxide, ≥97.0%
Sigma-Aldrich
Titanium(IV) isopropoxide, packaged for use in deposition systems