Isothiocyanates oxidation

Isothiocyanate oxide hydrobromides,164 however, all show the characteristic absorption in the imino region their cyclic disulfide structure (153) is thus indicated, presupposing the isomerization 153— 152 (R = alkyl) on liberation of the free base. When a rearrangement of this type can occur readily, it seems reasonable that the dithiazolidine form (153), incorporating the basic alkylimino group, would be the more stable in the presence of acid. 

The experimental evidence as a whole suggests that both isothiocyanate oxides and sulfides, in the form of their salts, possess the dithiazolidine structures 153 and 155, respectively the lower alkyl isothiocyanate oxides when liberated rearrange to the 1,2,4-thiadiazolidines (152), but the higher homologs do not. In the isothiocyanate sulfides,... 

Information concerning the infrared absorption spectra of 1,2,4-thiadiazoles is rather sparse, and existing data are listed in Table IX. Recent investigations have materially contributed to the elucidation of the structures of perthiocyanic and isoperthiocyanic adds and related compounds154, 155 (see Section III, J, 1) and of those of isothiocyanate oxides and sulfides164 (see Section II, D, 3). 

Chlorination of isothiocyanates produces iminohalomethylsulfenyl halides (269) which react further with isothiocyanates to yield dithiazolium salts of type (365). Treatment of (365) with 95% ethanol leads to the formation of salts of isothiocyanate oxides (366) whereas treatment with hydrogen sulfide produces salts of isothiocyanate sulfides (367), as indicated in Scheme 133 <65AHC(5)119>. Neutralization of salts (367) affords the free base isothiocyanate sulfides (368) which are stable with one exception. Melting or recrystallization of N,AT -dimethyliminothiono-l,2,4-dithiazolidine (368 R = Me) results in a Dimroth... 

The interconvertibility of 1,2,4-dithiazoles and 1,2,4-thiadiazoles has been known for a long time. Examples of such reactions have been encountered in the study of isoperthiocyanic acid (3-imino-l,2,4-dithiazolidine-5-thione) and its analogs (the thiurets , isothiocyanate oxides and sulfides ), and their elucidation has not been as easy matter.1,3 The interpretation of these, and of novel conversions of 1,2,4-dithiazoles to 1,2,4-thiadiazoles has more recently been greatly aided by the application of physical methods, including X-ray analyses. Since the reactions are not all of one kind, it has been expedient to describe them in two separate Sections, among the syntheses of type A and type C, respectively. 

The chemistry of the isothiocyanate oxides and sulfides for which 1,2,4-thiadiazole structures have been considered at various times3 (see especially... 

Other Reactions. 2-Dioxolaniniines, 2-oxathiolaniniines, and 2-oxa2o1idinimines result from the reaction of propylene oxide with isocyanates, isothiocyanates, and carbodiimides, respectively (103,104). 

Ethoxy-6-methylpyrimidine 1-oxide (499) reacts with phenyl isocyanate to eliminate carbon dioxide and give a mixture of 4-ethoxy-6-methyl-N-phenylpyrimidin-2-amine (SOO) and (the derived) 7V-(4-ethoxy-6-methylpyrimidin-2-yl)-7V,7V -diphenylurea (SOI) phenyl isothiocyanate reacts quite differently (79CPB2642). 

This thiourea, prepared from an amino acid and phenyl isothiocyanate, is cleaved by anhydrous trifluoroacetic acid (an N-COCF3 group is stable), and by oxidation (/72-CIC6H4CO3H, 0°, 1.5 h, 73% yield H2O2/ACOH, 80°, 80 min, 44% yield). ... 

In a manner analogous to classic nitrile iinines, the additions of trifluoro-methylacetonitrile phenylimine occur regiospecifically with activated terminal alkenes but less selectively with alkynes [39], The nitnle imine reacts with both dimethyl fumarate and dimethyl maleate m moderate yields to give exclusively the trans product, presumably via epimenzation of the labile H at position 4 [40] (equation 42) The nitrile imine exhibits exo selectivities in its reactions with norbornene and norbornadiene, which are similar to those seen for the nitrile oxide [37], and even greater reactivity with enolates than that of the nitnle oxide [38, 41], Reactions of trifluoroacetomtrile phenyl imine with isocyanates, isothiocyanates, and carbodiimides are also reported [42]... 

The special properties of lipoic acid arise from the ring strain experienced by oxidized lipoic acid. The closed ring form is approximately 20 kj higher in energy than the open-chain form, and this results in a strong negative reduction potential of about —0.30 V. The oxidized form readily oxidizes cyanides to isothiocyanates and sulfhydryl groups to mixed disulfides. 

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). 

Reactions of Heterocyclic N-Oxides with Trimethylsilyl Cyanide, Trimethylsilyl Azide, Trimethylsilyl Isothiocyanate, and Trimethylsilyl Halides... 

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