Sulphur Imines

The various sulphur imines are isoelectronic with sulphonium ylides, oxysulphonium ylides, sulphur dioxide, sulphoxides, or sulphones. Their chemistry has been reviewed briefly by Field and extensively by Roesky. All such imines are dealt with here with the exception of the. S-Cdihalogeno)-N-substituted iminosulphuranes, for coverage of which readers are referred to the Roesky review and to two leading references.  

Iminosulphuranes.—New results have been reported for three preparative routes to iminosulphmanes. Ando et al have shown that under photochemical conditions methyl azidoformate and methyl sulphide will form the sulphidimine (95), but in the presence of a triplet sensitizer only methyl 

Venier, ISth Annual Report of the Petroleum Research Fund of the American Chemical Society, 1970, p. 16. 

Migita, Bull. Chem. Soc. Japan, 1971, 44, 2278. 

Claus and Yycudilik have reported the details of the dehydration reaction catalysed by phosphorus pentoxide between DMSO and aryl amines to afford iminosulphuranes in good yield. Lerch and Moffatt have reported that the DMSO-DCC oxidation reaction could be applied to iminosulphurane synthesis simply by the addition of an aryl amine to the reaction mixture rather than the usual alcohol. In both instances the mechanism probably involved displacement from sulphur by the amine of an oxy-leaving group (a pyrophosphate or a urea). The latter workers found that hydrazines could not be used in the place of the aryl amine, probably because of subsequent intramolecular eliminations by the iminosulphuranes. 

Tamura, K. Sumoto, J. Minamikawa, and M. Ikeda, Tetrahedron Letters, 1972, 4137. 

Hayashi and Swern have reported additional examples of the third method, the photochemical coupling of azides with sulphides, which probably occurs through attack of singlet nitrene on sulphur. The earlier reported reaction of a sulphinyl azide with a sulphoxide to afford a N-sulphonyUmine now has been found to occur with retention of configuration about sulphoxide-sulphur. Okahara et aC have reported additional examples of the oxidative coupling of sulphonamides with dimethyl sulphide to afford imines in good yield. 

N-Tosyliminosulphuranes could be hydrolysed in concentrated sulphuric acid to afford the free iminosulphurane. However, in dilute acid the hydrolysis proceeded normally to afford a sulphoxide and a 

Funikawa, T. Omata, T. Yoshimura, T. Aida, and S. Oae, Tetrahedron Letters, 1972,1619. 

N-Aryliminosulphuranes earlier had been reported to undergo Sommelet-type rearrangements. Claus and Rieder studied the kinetics of the rearrangement of (123) and concluded that the rate was determined by the 

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The reactions of triphenylphosphazenyl derivatives with many other electrophilic species have been described. With sulphur tetrafluoride, sulphur imines are formed, possibly via the four-centred intermediate (24) ... 

The reaction proceeds by way of the imine (109) which is converted into the enamine (110) by proto tropic rearrangement before being cyclised with concentrated sulphuric acid. 

Unlike our initial imine disconnection which is restricted to nitrogen heterocycles (with one or two specific exceptions such as pyrylium salts, see Chapter 9), the heteroatom in the enamine or enamine-like disconnection could be divalent. Therefore this disconnection is also applicable to oxygen-and sulphur-containing heterocycles, typified by 1.24 and 1.25. 

Yet another method for the preparation of hydroxycitronellal (35) has been developed it depends on the fact that the immonium salt (36) is hydrated by aqueous sulphuric acid, hydrolysis of the imine group taking place with sodium hydroxide. The effect of catalysts supported on silica gel on the well-known thermal conversion of citronellal to isopulegol has been studied. The abstract... 

The only other commonly reported technique is the acid-catalysed evolution of nitrogen gas. Typically, sulphuric acid is used as the catalyst . This is not totally reliable, however. Coombsreports that if carbon-nitrogen cleavage will yield a stable carbonium ion, then formation of HN3 predominates over loss of N2 and formation of imine. This is contradicted, however, by the report that i-butyl azide in the presence of sulphuric acid yields acetone-A-methylimine which subsequently hydrolyses to give acetone, isolated as its 2,4-dinitrophenylhydrazone. 

Treatment of iV-benzhydrylidene azidobenzhydrylamine (28) with trifluoroacetic acid at room temperature for 2 hr yielded 79% benz-anilide (33) and 65% benzophenone imine (34) Similar results could be obtained using concentrated sulphuric acid at room temperature, or aluminium chloride and gaseous hydrogen chloride at... 

The reaction was discovered in 1923 in interesting circumstances. Products from the decomposition of hydrazoic acid in various solvents were investigated and the decomposition catalysed by sulphuric acid in benzene was found to lead to aniline Schmidt considered an imine radical NH to be the species responsible and on attempting to trap this with benzophenone he obtained benzamide. The reacdon was generalized and rapidly exploited, mainly by its discoverer. The currently accepted mechanism was proposed in outline shortly after-wards and is shown in its modern form in scheme (19) for carboxylic... 

Nitrosolysis of camphor ethyl acetal with ethanolic ethyl nitrite in sulphur dioxide yields the orthoester oxime (205) which is rapidly dehydrated by excess acetal to the orthoester nitrile which then reacts with sulphur dioxide to form the ester nitrile and diethyl sulphite.Further papers in this section include the full paper on ozonolysis of silyl ethers (Vol. 5, p. 33), another synthesis of camphor-enol trimethylsilyl ether (cf. Vol. 6, p. 41)/°° the conversion of camphor oxime with Grignard reagents into the corresponding imine with no aziridine formation/° the preparation of (206) by treating bornylene with trichloroacetyl isocyanate/ the oxidation of thiocam-phor to the 5-oxide and alkylation in the presence of thallium(i) ethoxide to a/S-unsaturated sulphoxides/ and the free-radical C-3 alkylation of camphor with alkenes. " ... 

The complex photochemistry of cysteine derivatives sensitized by 4-carboxy-benzophenone 15 has been unravelled by CIDNP. The initially formed sulphur-centred (see. Figure 19) radical decarboxylates rapidly to give an a-amino alkyl radical, which in turn cleaves into a thiyl radical R-S and a vinylamine in competition with being oxidized to an imine by surplus sensitizer all these resulting species are unstable themselves and undergo further reactions. The rates of the radical fragmentations and the radical oxidation were obtained from the CIDNP experiments. 

Benzene-induced solvent shifts have been used in structural and stereochemical studies in a number of sulphur-136-139 j phosphorus-containing compounds, ethylenedi-imine complexes and nitro-... 

The photochemical decomposition of the thiazete 207 in benzene at 30 °C affords carbazole 208190. The reaction presumably involves the formation of a biradical by S—N bond fission which, on loss of S02, undergoes cyclization to yield the final product. Loss of sulphur dioxide also occurs on irradiation of the sultam 209 yielding the quinomethane imine 210, which ring closes to the azetidine 211181. Irradiation of the sulphobenzimide 212 in benzene yields the amide 213 by a free radical reaction path182. 

Nitrogen analogues (5) of o-xylylenes are produced as transient intermediates in the flash pyrolysis of o-amino-benzyl alcohols (4). They do not undergo ring-closure to benzazetines but cyclize to acridines via dihydroacridines. Possibly the same type of imine methide is involved in the thermal and photochemical extrusion of sulphur dioxide from the cyclic sulphones (6), which in this case does give the benzazetine. ... 

NMeTos, reacts with ammonia to give 1-methyl-1,2,4-triazole (577). Cycloaddition of thionitrosodimethylamine, Me2N—N=S, to the tetrazine ester (578) yields the triazole (579) with extrusion of nitrogen and sulphur.The formation of the triazolinones (580) from AT-phenylbenzonitrile imine (PhC=N—NPh) and aroyl azides involves a Curtius rearrangement of the latter to aryl isocyanates. 

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