- 2-Nitroso-N-arylanilines: Products of acid-promoted transformation of σH adducts of arylamines and nitroarenes
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Anions generated from arylamines react with substituted nitrobenzenes to form σH adducts, which, under protonation with acetic acid, undergo transformation to 2-nitroso-N-arylamines, susceptible to reduction, condensation and cyclization reactions. Georg Thieme Verlag Stuttgart.
- Wróbel, Zbigniew,Kwast, Andrzej
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p. 1525 - 1528
(2008/02/04)
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- Acetamidinosulphenylation of Alkynes via Electrophilic Addition of 4'-Substituted Benzenesulphenanilides in Acetonitrile
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A number of 4'-substituted benzenesulphenanilides and N-methyl-4'-nitrobenzenesulphenanilide are shown to add to simple alkynes in acetonitrile in the presence of boron trifluoride-diethyl ether to give acetamidinovinyl sulphides in varying yields.Addition is largely favoured by dialkyl substitution on the alkyne and by electron-attracting anilide substituents.Moreover, the azasulphenylation adducts are produced with trans stereospecificity and high regioselectivity (Markovnikov orientation).A likely mechanism involves nucleophilic displacement by the alkyne at the activated sulphur of the anilide complexed with boron trifluoride leading to the initial formation of a thiirenium ion intermediate.Subsequent back-side attack of acetonitrile on the thiirenium ion gives a nitrilium ion which is ultimately trapped by the liberated arylamine.
- Benati, Luisa,Montevecchi, P. Carlo,Spagnolo, Piero
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p. 1105 - 1111
(2007/10/02)
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- BORON TRIFLUORIDE PROMOTED REACTION OF BENZENESULPHENANILIDES WITH ALKENES
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The boron trifluoride-promoted reaction of a series of 3'- and 4'-substituted benzenesulphenanilides (1) with various alkenes has been investigated as a potential synthetic route to arylaminosulphides.The benzenesulphenanilides (1) investigated generally afford arylaminosulphenylation adducts in fair to good yields except for the methoxy-substituted anilides (1e and f), which largely lead to decomposition products under comparable conditions.In all cases examined, the addition proceeds with trans-stereospecificity and, with terminal alkenes, leads regioselectively to the exclusive (or predominant) formation of the terminal sulphides.The findings are interpreted by assuming that boron trifluoride transforms the sluggish benzenesulphenanilides (1) into reactive electrophilic species, which can undergo nucleophilic attack at sulphur by an alkene, presumably affording episulphonium-borate ion-pair intermediates, in competition with attack by another sulphenanilide unit.
- Benati, Luisa,Montevecchi, P. Carlo,Spagnolo, Piero
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p. 1145 - 1156
(2007/10/02)
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- Benzenesulphenanilidyl Radicals. Part 3. Reactions of 4'-Substituted Benzenesulphenanilides with t-Butoxyl Radicals
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Decomposition products of the 4'-substituted benzenesulphenanilidyl radicals (2a, b, d, and e), generated from the corresponding benzenesulphenanilides (1) with t-butoxyl radicals, have been investigated in benzene, acetonitrile, and acetone.Results indicate that the decomposition modes exhibited by these radicals are not essentially influenced by variation of the solvent polarity; comparison of the findings with present and previous results from oxidation of (1) with lead dioxide show that the chemical reactivity trend displaced by the thioaminyls (2) can be greatlyinfluenced both by the reaction medium and the 4'-substituent.Evidence is presented that the benzenesulphenanilides (1b) and (1e) react in acetone in the presence of di-t-butyl hyponitrite to give products ascribable to homolytic substitution at the sulphenanilide sulphur by acetonyl radicals.
- Benati, Luisa,Montevecchi, P. Carlo,Spagnolo, Piero
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p. 1577 - 1582
(2007/10/02)
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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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- Benzenesulphenanilidyl Radicals. Part 2. Substituent and Solvent Effects on the Reactivity of 4'-Substituted Benzenesulphenanilidyl Radicals Produced by Oxidation with Lead Dioxide of the Corresponding Benzenesulphenanilides
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Oxidation of benzenesulphenanilide (1d) with lead dioxide in benzene affords the p-benzoquinone diimine (5d) together with minor amounts of N,N-bis(phenylthio)aniline (4d) and diphenyl disulphide (7a).The formation of the products is explained in terms of p-C-N coupling of the benzenesulphenanilidyl radicals (2d) and subsequent fragmentation of the resulting dimer.A similar trend is observed in the oxidation of 4'-chloro- and 4'-bromo-benzenesulphenanilides (1e) and (1f), whereas 4'-nitrobenzenesulphenanilide (1g) leads to the o-phenylenediamine (12g), arising from o-C-N coupling of the sulphenanilidyl radical (2g).The oxidation of the sulphenanilides (1e) and (1f) in acetonitrile produces the phenazines (3e) and (3f) and the disulphide (7a), whereas the anilide (1g) and 4'-cyanobenzenesulphenanilide (1h) give azobenzenes (11g) and (11h) and the disulphide (7a); these results are discussed in terms of a possible mechanism involving oxidation of the N-N dimers (14e-h) which are in rapid equilibrium with the corresponding sulphenanilidyl radicals (2e-h).Evidence is also presented that the oxidation of 2-nitrobenzenesulphenanilides leads to products ascribable to intermediate 2-nitrobenzenesulphenanilidyl radicals, in contrast with a previous claim.
- Balboni, Claudio,Benati, Luisa,Montevecchi, P. Carlo,Spagnolo, Piero
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p. 2111 - 2117
(2007/10/02)
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- Studies on Sulfenamides. VII. Anodic Oxidation of 3'- and 2'-Substituted 2-Nitrobenzenesulfenanilides
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Controlled potential electrolysis of 2'-(p-chlorophenyl)amino-4'-chloro-2-nitrobenzenesulfenanilide (4c) gave 2,7-dichlorophenazine in good yield.This result suggested that in the electrolysis of 4'-substituted 2-nitrobenzenesulfenanilides the ring closure to form the 2,7-disubstituted phenazines takes place through the binding of the nitrenium ion (B) to the 2'-position of the sulfenanilides.As for the 3'- and 2'-substituted 2-nitrobenzenesulfenanilides, most of the nitrenium ions bind to the 4'-position and are oxidized further to the p-quinonediimine derivatives, and most of these are oxidized further to unidentified resinous compounds.Keywords: anodic oxidation; 2-nitrobenzenesulfenanilides; 2,7-disubstituted phenazines; oxidation of sulfenamides; nitrenium ion; benzoquinonediimines
- Sayo, Hiroteru,Mori, Koichi,Michida, Takashi
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p. 3782 - 3785
(2007/10/02)
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