Addition to isothiocyanate

It is worth noting that the same kind of reactions can be carried out by tin-radical-mediated ring closure of analogous isothiocyanates e.g., 33, 37, 39, NC = NCS) [22b,c], In this case, the intermediate a-thio-substituted imidoyl radical is generated by addition of a stannyl radical to the sulfur atom of the isothiocyanate. Although it had been known for a few decades, this way to imidoyl radicals had found very little application in organic synthesis. Bachi s work was the first example of synthesis of heterocyclic compounds by radical addition to isothiocyanates, showing the way to further possible applications [9]. 

In addition to isothiocyanates, compounds having the configuration RN=C(SX)2 (X = alkyl or K) react rapidly with chlorine to produce carbonimidoyl dichlorides. Thus, Neidlein and his co-workers and Gompper and Kunz ( )obtained arylsulfonylcarbonimidoyl dichlorides X in the reaction of S,S-dialkyl-N-sulfonyldithiocarbonimides XI with chlorine. 

The decomposition corresponds to a Lossen s rearrangement of a hydroxamic acid. In addition to isothiocyanates, rhodanides and nitriles have been observed among the reaction products. 

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). 

The 1,2,3,4-thiatriazoles are unstable. They decompose on heating— in some cases even at room temperature—and in many cases they melt with detonation. Accordingly the Ng-group has not been stabilized much by ring closure. The compounds behave in this respect similarly to azides and this fact doubtlessly delayed the recognition of their true nature. On heating with a solvent the thermal decomposition of 5-aryl-1,2,3,4-thiatriazoles proceeds according to Eq. (4). By the photochemical decomposition small amounts of the isothiocyanate, RNCS, are formed in addition to the nitrile. ... 

Natural products have been noted for their potential health benefits from time immemorial and are the basis of Ayurveda, an ancient Indian medical practice (Bushkin and Bushkin, 2002). However, the potential benefits of several natural products reside in one or two active ingredients. For example green tea stands for polyphenols, soy for soy estrogens, broccoli for isothiocyanates and grape seed for polyphenols. The beauty of rice bran is that there are more than 100 antioxidants, several categories of bioactive phytonutrients, such as IP6, polyphenols, phytosterols, tocotrienols, y-oryzanol, B vitamins, minerals and trace minerals in addition to fat, protein, fiber, polysaccharides and other nutrients. These phytonutrients and antioxidants of rice bran are believed to act at the cellular level, and their synergestic function is responsible for the positive health benefits. 

TRITC is relatively insoluble in water, but it can be dissolved in DMF or DMSO as a concentrated stock solution prior to its addition to an aqueous reaction mixture. The isothiocyanate group is reasonably stable in aqueous solution for short periods, but will degrade by hydrolysis. TRITC also is more stable to photobleaching than FITC (Section 1, this chapter), and its absorption and emission spectra are less sensitive to environmental conditions, such as plT. It is best, however, to use only fresh reagent for modification purposes. Storage should be done under desiccated conditions, protected from light, and at -20°C. 

In addition to the wide range of commercial probes, many other fluorescent molecules have been synthesized and described in the literature. Only a handful, however, are generally used to label antibody molecules. Perhaps the most common fluorescent tags with application to immunoglobulin assays are reflected in the main derivatives produced by the prominent antibody manufacturing companies. These include derivatives of cyanine dyes, fluorescein, rhod-amine, Texas red, aminomethylcoumarin (AMCA), and phycoerythrin. Figure 20.16 shows the reaction of fluorescein isothiocyanate (FITC), one of the most common fluorescent probes, with an antibody molecule. 

Addition of Grignard reagent to isothiocyanates provides secondary thioamides.24... 

In addition to these systematic studies of lanthanide sulfoxide complexes, with variation in both sulfoxide and anion, other more isolated reports are available. Lanthanide isothiocyanate complexes of the cyclic sulfoxides thioxane oxide (490) and tetramethylene sulfoxide (493) have been synthesized and complexes of the unusual potentially chelating ligand 2-(ethylsulfinyl)pyridine-V-oxide (63) described. Detailed studies of the solvation of lanthanide-shift reagents by Me2SO have also appeared (178,179). 

These authors also demonstrated that the outcome of analogous additions of lithiated alkoxyallenes 120 to isothiocyanates is highly dependent on the nature of the alkyl group in the isothiocyanates as depicted in Schemes 8.34and 8.35 [88, 91]. Whereas methyl isothiocyanate 134 leads to pyrrole derivative 135, the correspond-... 

The carbon in the isothiocyanate grouping is highly susceptible to nucleophilic attack by the peptide s free amino group. Overall addition to the C=N creates a thiourea derivative. Making the conditions strongly acidic then promotes nucleophilic attack by the sulfur of the thiourea on to the carbonyl of the first peptide bond, producing a five-membered thiazoline heterocycle. Proton loss occurs from the nitrogen, and this creates an intermediate that is equivalent to the addition product in simple acid-catalysed amide... 

Addition of isothiocyanates to 2-amino-4H-pyran-3-carbonitriles with subsequent cyclization affords pyrano[2,3-d]pyrimidinethiones-2 290 (89JPR971, 08PS1145) (Scheme 121). 

The reaction of the same bismuthonium ylide with isothiocyanates in the presence of a copper(H) catalyst afforded the sulfur-incorporated spiro-cyclic compound as the main product, in addition to a small amount of carbon-carbon bond formed products (Scheme 12) [28],... 

The amino group of 3-amino-1,2,4-oxadiazoles shows little nucleophilic character. For example, addition to phenyl isothiocyanate to give 3-(phenylthioureido) compounds requires heating of the components without solvent at 120-130 °C or the use of polar aprotic solvents (DMSO, DMF) and long reaction times (30 days at 23°C) <77JCS(P1)1616>. 3-(Thioureido)-1,2,4-oxadiazoles undergo fast ring transformations to thiadiazoles (see Section 4.04.5.1.1). 

Figure 5 Modes of addition of isothiocyanates to thiatriazoline-5-imines.

A species of Halichondria from the Marshall Islands contained an isothiocyanate (249) [255] and an isothiocyanate based on the guai-6-ene skeleton (250) was isolated from an unidentified sponge from Japanese waters [256]. Acanthella pulcherrima from Australia contained two isothiocyanates (251-252), in addition to known sesquiterpenes [257]. 

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