- Regioselective Ortho‐C–H sulfenylation of free phenols catalyzed by Co(II)-immobilized on silica-coated magnetic nanoparticles
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Fe3O4?SiO2-UT?CoII is prepared by the silica-coated magnetic nanoparticles, urea-triazole, and CoCl2. This organic-inorganic hybride composite showed a good to excellent catalytic activity toward regioselective ortho-sulfenylation of free phenols and naphthols using pivalic anhydride as a directing group, also K2S2O8 and PPh3 were employed as oxidant and additive respectively. The newly synthesized catalyst was fully characterized by using different techniques such as FT-IR, TGA, DTG, TEM, SEM, EDS, ICP and VSM analyses. The competitive price, accessibility and lower toxicity of cobalt compared to expensive transition metals using for C–H bond activation and functionalization constitute precious advantages for this method. Moreover, this heterogeneous catalyst could be magnetically recovered and reused without significant loss of its catalytic activity after five cycles.
- Khaef, Sepideh,Rostami, Abed,Khakyzadeh, Vahid,Zolfigol, Mohammad Ali,Taherpour, Avat Arman,Yarie, Meysam
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- Co(II)-catalyzed regioselective clean and smooth synthesis of 2-(aryl/alkyl-thio)phenols via sp2 C-H bond activation
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The first example of a smooth, practical and useful strategy for the preparation of ortho-aryl/alkyl sulfenyl phenols by using the reaction of aryl/alkyl thiols with phenols in the presence cobalt as catalyst, and with the assistance of acetic anhydride as directing group via C-H bond activation, was developed. Described method enables to form selectively C-S bond without any ligand, oxidant, and aryl/alkyl halide under mild conditions.
- Rostami, Abed,Khakyzadeh, Vahid,Zolfigol, Mohammad Ali,Rostami, Amin
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p. 260 - 263
(2018/05/04)
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- Acid-promoted Decomposition of Benzenesulphenanilides and N-Aryl Bis(benzenesulphen)amides
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The decomposition of 4'-substituted benzenesulphanilides (1a-d) in the presence of trifluoroacetic acid (0.6 equiv.) leads to N-arylbis(benzenesulphen)amides (6a-d) in variable yields, depending on the 4'-substituent, in addition to disulphide (4) and anilines (3a-d), whereas products arising from sulphenylation of the N-aryl ring result from 3'-methoxybenzenesulphenanilide (1g).The 4'-nitro- and 3'-nitro-benzenesulphenanilides (1e,f) react with a slight excess of trifluoroacetic acid to give only (4), the thiosulphonate (5), and aniline (3e,f).The findings are interpreted in terms of possible nucleophilic attack at the S-N bond of a protonated sulphenanilide by the nitrogen or the N-aryl ring of another sulphenanilide unit, according to the nature of the substituent and its position, with displacement of aniline (3).The reaction of (1a-d) with 1.5 equiv. of trifluoroacetic acid leads to complete disappearance of the initially formed amides (6a-d) with concomitant formation of phenazines (9) and/or p-quinone di-imines (8).Similar results are obtained by using boron trifluoride-diethyl ether.Di-imines (8) and phenazines (9) are explained on the basis of a mechanism initially involving nucleophilic attack by (1) and/or (6) and/or (3) at the ortho and para positions of an intermediate cation, possibly (18A) or (18B), and loss of the disulphide (4).
- Benati, Luisa,Montevecchi, P. Carlo,Spagnolo, Piero
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p. 2261 - 2266
(2007/10/02)
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