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• 80-48-8 methyl p-toluene sulfonate 
• 529477-58-5 N-(hydroxy)-5-(p-methoxyphenyl)-4-methylthiazole-2(3H)-thione 

Relevant academic research and scientific papers

4- and 4,5-substituted N-methoxythiazole-2(3H)-thiones - Preparation, UV/Vis spectra, and assignment of electronic transitions in comparison to N-methoxypyridine-2(1H)-thione using time-dependent density functional theory calculations

Experimentally observed absorptions in UV/Vis spectra of N-methoxy-4-methylthiazole-2(3H)-thione, N-methoxy-5-(p-methoxyphenyl)-4- methylthiazole-2(3H)-thione, N-methoxy-pyridine-2(1H)-thione, and selected N-hydroxy derivatives thereof have been assigned to π→π*-type transitions as dominating character, using the results from ab initio calculations [time-dependent density functional theory (TD)RI-BLYP/ TZVPP]. Theory further predicts that electronic excitations in N-methoxythiazole-2(3H)- thiones on one side and N-methoxypyridine-2(1H)-thione on the other side differ significantly with respect to character and statistical weight of contributing transitions. These effects originate predominantly from contributions of the endocyclic sulfur atom onto orbital energies and shapes in thiazole-2(3H)- thiones, and may be intensified by substituents such as a p-methoxyphenyl group located in position 5. Since the majority of the calculated spectral differences between thiazole- and pyridinethiones refers to excitations of low intensity, the findings from the present study correlate with two important experimental facts: (i) Apart from minor shifts in the exact spectral location of UV/Vis absorptions, electronic spectra of N-hydroxy- or N-methoxy-substituted pyridine-2(1H)-thiones and thiazole-2(3H)-thiones are surprisingly similar in shape, (ii) N-alkoxy-pyridine-2(1H)-thiones and N-alkoxythiazole-2(3H)-thiones liberate upon UV/Vis excitation oxygen-centered radicals with a comparable efficiency. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.

Efficiency of alkoxyl radical product formation from 5-substituted 3-alkoxy-4-methylthiazole-2(3H)-thiones

In a comparative study, reactions between 5-(p-methoxyphenyl)-substituted 3-alkoxy-4-methylthiazole-2(3H)-thiones and appropriate mediators (BrCCl3, Bu3SnH) provided higher yields of alkoxyl radical products (δ-bromohydrins, cyclic ethers, carbonyl compounds) than respective transformations of 5-phenyl- and 5-methyl-substituted derivatives. The unusual selectivity of applied thiohydroxamates to furnish products of O-alkylation, even upon treatment with soft carbon electrophiles, and the marked propensity of 3-alkoxy-5-(p-methoxyphenyl)-4-methylthiazole-2(3H)-thiones to crystallize, facilitated preparation and purification of the new family of alkoxyl radical precursors in a noteworthy manner.

Aspects of structural thiohydroxamate chemistry-on a systematic in the 5-(p-methoxyphenyl)-4-methylthiazole-2(3H)-thione series

Bond angles at thiohydroxamate oxygen in crystal structures of 3-alkoxy-5-(p-methoxyphenyl)-4-methylthiazole-2(3H)-thiones gradually increased with the size of the 3-alkoxy substituent. This effect was attributed to strain on the basis of (i) a linear free energy relationship (Taft-Dubois correlation) and (ii) signal coalescence from resonances of diastereotopic CH3 groups in solution (O-cumyl substituent; DNMR). Substitution at oxygen along the sequence OR (R=prim-, sec-, and tert-alkyl), OH, and OLi was reflected in a gradual decrease of N,O distances and lengthening of associated C,S bonds. The responsivity for these changes was more pronounced in the thiazole-2(3H)-thione than in the pyridine-2(1H)-thione series.

Spin trapping of alkoxyl radicals generated from 5-methyl and 5-aryl-3-alkoxy-4-methylthiazole-2(3H)-thiones in photochemically induced and microwave-initiated reactions

Methoxyl and isopropoxyl radicals were generated from N-alkoxy-4,5-dimethylthiazole-2(3H)-thiones (λmax～320 nm) and 5-aryl derivatives (aryl=p-XC6H4; X=MeO, H, AcNH, Cl) (λmax～335 nm) in photochemically and microwave-induced reactions. Alkoxyl radicals were trapped with dimethylpyrrolidine N-oxide and characterized as spin adducts via EPR. Cumyloxyl radicals were liberated in a similar manner from N-cumyloxy-5-(4-methoxyphenyl)-4-methylthiazole-2(3H)-thione. A noteworthy bathochromic shift was found for the lowest energy transition of N-(hydroxy)indeno[2,1-d]thiazole-2(3H)-thione (λmax=376 nm), if compared to the UV-vis absorption of N-hydroxy-4-methyl-5-phenylthiazole-2(3H)-thione (λmax=338 nm). Syntheses of alkoxyl radical precursors and procedures for conducting N,O-homolysis are described in a full account.