Sulfur isothiocyanates

V. Sulfur Isocyanate Pentafluoride and Sulfur Isothiocyanate Pentafluoride... 

Sulfoxides occur widely in small concentrations in plant and animal tissues, eg, aHyl vinyl sulfoxide [81898-53-5] in garlic oil and 2,2 -sulfinylbisethanol [3085-45-8] as fatty esters in the adrenal cortex (1,2). Homologous methyl sulfinyl alkyl isothiocyanates, which are represented by the formula CH3SO(CH2) NCS, where n = 3 [37791-20-1], 4 [4478-93-7], 5 [646-23-1], 8 [75272-81-0], 9 [39036-83-4], or 10 [39036-84-5], have been isolated from a number of mustard oils in which they occur as glucosides (3). Two methylsulfinyl amino acids have also been reported methionine sulfoxide [454-41-1] from cockroaches and the sulfoxide of i -methylcysteine, 3-(methylsulfinyl)alaiiine [4740-94-7]. The latter is the dominant sulfur-containing amino acid in turnips and may account in part for their characteristic odor (4). 

Several related derivatives have also been utilized in this type of synthesis. Imino-chloromethanesulfenyl chlorides (184), prepared by the controlled addition of chlorine to isothiocyanates, react with amidines (161) to give 1,2,4-thiadiazolines (185) (71T4117). Chlorocarbonylsulfenyl chloride (186), prepared by the hydrolysis of trichloromethanesulfenyl chloride with sulfuric acid, reacted with ureas, thioureas and guanidines to give 1,2,4-thiadiazolidine derivatives (187) <70AG(E)54, 73CB3391). 

Heating or irradiating alkenes in the presence of sulfur gives relatively low yields of thiiranes. For example, a mixture of sulfur and norbornadiene in pyridine-DMF-NHa at 110 °C gave a 19% yield of the monoepisulfide of norbornadiene as compared with a 78% yield by the method of Scheme 120 (79JCS(Pi)228). Often 1,2,3-trithiolanes are formed instead of thiiranes. The sesquiterpene episulfides in the essential oil of hops were prepared conveniently by irradiation of the terpene and sulfur in cyclohexane (Scheme 135) (80JCS(Pl)3li). Phenyl, methyl or allyl isothiocyanate may be used as a source of sulfur atoms instead of elemental sulfur. 

A major advance was devised by Pehr Edrnan (University of Lund, Sweden) that has become the standard method for N-terminal residue analysis. The Edman degradation is based on the chemistry shown in Figure 27.12. A peptide reacts with phenyl isothiocyanate to give a phenylthiocarbamoyl (PTC) derivative, as shown in the first step. This PTC derivative is then treated with an acid in an anhydrous medium (Edrnan used nitrornethane saturated with hydrogen chloride) to cleave the amide bond between the N-terminal anino acid and the remainder of the peptide. No other peptide bonds are cleaved in this step as amide bond hydrolysis requires water. When the PTC derivative is treated with acid in an anhydrous medium, the sulfur atom of the C=S unit acts as... 

Elemental sulfur undergoes nucleophilic attack by amines at low temperatures. Therefore the conjugate position of an enamine is sufficiently nucleophilic to attack elemental sulfur and yield thiolated intermediate 103. When 103 is treated when phenyl isothiocyanate, the cyclic adduct 104... 

Reactions of enamines with isocyanates (568) and isothiocyanates (569) in the presence of sulfur gave l,3-thiazolidine-2-ones and l,3-thiazolidine-2-thiones. 

Cycloaddition of 2-nitrosopyridine 48 with nitrile oxides can give either di-A -oxides such as 49 or 3-mono-A -oxides such as 50 (93JHC287). In general, greater electron withdrawing character in the aromatic substituent appears to favor formation of the di-A -oxides. Sulfur ylides such as compound 51 are obtained from aryl isothiocyanates and l-amino-2-methylthiopyridinium iodides (84JCS(P1)1891) nitrogen ylides can be obtained from a similar reaction (86H(24)3363). 

Allylamine has been prepared from allyl isothiocyanate by hydrolysis with dilute sulfuric 1 or hydrochloric2 acid. 

Corriu et al. also described an alternative synthetic method for internally coordinated silanethiones starting from the pentacoordinated diaminosilanes.28 As shown in Scheme 9, the pentacoordinated diaminosilanes 32 are allowed to react with sulfur-containing heterocumulenes such as carbon disulfide or phenyl isothiocyanate to give the corresponding insertion products 33, which undergo thermal decomposition to produce the corresponding silanethiones 31, 34, and 35.28... 

A straightforward preparation of pyrimidinones and pyrimidinethiones 45 involved reaction of isocyanates or isothiocyanates with the readily available starting material 44, which had previously been described by the same authors. A particularly interesting application was the use of sugar isothiocyanates to give nucleosides. Nucleophilic displacements of the sulfur groups in the products were also reported <06EJO634>. 

Amidines and cyclic amidines are also converted into 1,2,4-thiadiazoles by reaction with isothiocyanates, imino-sulfenyl chlorides, di- and trichloromethyl sulfenyl chlorides, and carbon disulfide in the presence of sulfur. Ureas, thioureas, guanidines, carbodiimides, and cyanimides react with chlorocarbonylsulfenyl chloride to produce 1,2,4-thiadiazol-5-one derivatives in another example of a type B synthesis <1996CHEC-II(4)307>. 

Cyclic thiourea derivatives having three different types of cyclophane structure (ortho-meta, meta-meta and meta-para) and a lariat-type thiourea have been synthesized, using reaction of isothiocyanate with amine.230 Cyclic thioureas have been obtained from formaldehyde aminals and sulfur (Sg) (Scheme 77).231... 

Carbon disulfide, the all sulfur equivalent of isothiocyanates, was found to react with benzimidazole 127 very rapidly under microwave irradiation to produce 128 <00TL5857>. 

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