Isothiocyanates, aromatic

Keywords aryl isothiocyanate, aromatic primary amine, diaryl thiourea... 

Fluotination of aromatic isothiocyanates occurs much more readily than that of alkyl isothiocyanates. Alcohols treated with IF ia DMF give 30—70% yields of their respective formates. 

Amides result from the reaction of aromatic hydrocarbons with isocyanates, such as phenyl isocyanate [103-71-9], ia the presence of aluminum chloride. Phenyl isothiocyanate [103-72-0] similarly gives thioanilides (136). 

AletalHydrides. Metal hydrides can sometimes be used to prepare amines by reduction of various functional groups, but they are seldom the preferred method. Most metal hydrides do not reduce nitro compounds at all (64), although aUphatic nitro compounds can be reduced to amines with lithium aluminum hydride. When aromatic amines are reduced with this reagent, a2o compounds are produced. Nitriles, on the other hand, can be reduced to amines with lithium aluminum hydride or sodium borohydride under certain conditions. Other functional groups which can be reduced to amines using metal hydrides include amides, oximes, isocyanates, isothiocyanates, and a2ides (64). 

Hydrazinopyridazines are easily formylated with formic acid or ethyl formate and acety-lated with acetic anhydride. A-Pyridazinylthiosemicarbazides are obtained from thiocyanates or alkyl- and aryl-isothiocyanates. Hydrazinopyridazines condense with aliphatic and aromatic aldehydes and ketones to give hydrazones. 

Reaction of lithiated allene with methoxymethyl isothiocyanate afforded 107, after trapping with methyl iodide. The newly formed 107 isomerizes under mild conditions to triene 108. This compound is ideally setup to experience an electrocyclization to dihydropyridine 109. Heating in the presence of acid facilitates aromatization of 109 to pyridines 110. 

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). 

Aliphatic and aromatic isothiocyanates and isoselenocyanates react with benzopentathiepin to give l,3-benzodithiol-2-imines 14.412... 

A Wittig-type reaction of iminophosphorane 995 with benzoyl and ethoxycarbonyl isocyanates gave (91T6747) thiadiazolotriazines 996, whereas reaction of 995 with aromatic isocyanates afforded 997. On the other hand, iminophosphorane 995 reacted with methyl and benzyl isothiocyanates to give 998. Reaction of 995 with acid chlorides gave 999 (88H1935). All these compounds display mesoionic or zwitter ionic character (Scheme 184). 

Aliphatic methyl ketones (CH3C(0)CH3) Simple aromatic nitro compounds (NO+CO) Straight-chain mercaptans Thiocyanates and isothiocyanates... 

Flamers R. J., Coulter S. K., Ellison M. D., Flovis J. S., Padowitz D. F., Schwartz M. P., Greenlief C. M., Russell J. N. Jr Cycloaddition Chemistry of Organic Molecules With Semiconductor Surfaces Acc. Chem. Res. 2000 33 617 624 Keywords carbonyi group, semiconductor materiais, surface reaction, aikenes, aromatic compounds, azo compounds, cycioaikadienes, isothiocyanates, unsaturated compounds... 

N-Substituted amides can be prepared by direct attack of isocyanates on aromatic rings.The R group may be alkyl or aryl, but if the latter, dimers and trimers are also obtained. Isothiocyanates similarly give thioamides. The reaction has been carried out intramolecularly both with aralkyl isothiocyanates and acyl isothiocyanates.In the latter case, the product is easily hydrolyzable to a dicarboxylic acid this is a way of putting a carboxyl group on a ring ortho to one already there (34 is... 

Analogous to the synthesis of isocyanates, isothiocyanates are obtained in good yield by reacting AyV -thiocarbonyldiimidazole (ImCSIm) with primary aliphatic or aromatic amines in equimolar amount. In chloroform at room temperature the dissociation equilibrium of imidazole-A-thiocarboxamides is shifted completely to isocyanates. 

Following the strategy described above involving ipso-fhioro displacement and subsequent reduction, the resulting ortko-phenylenediamines were treated with several aromatic isothiocyanates in the presence of N,N -dicyclohexylcarbodiimide... 

The reaction of l-benzyl-4-(acetylimido)-l/7-[l,2,4]triazolium inner salt 120 (an azomethine imine) with aromatic isothiocyanates yields among other products 5-acetyl-6-(arylimino)-l,5,6,7-anhydro[l,2,4]triazolo[3,4-A][l,3,4]thiadia-zoles 121 (Equation 34) <1984CCC1713>. 

In the aromatic series, however, the reaction at once proceeds further. From the dithiocarbamate first formed, hydrogen sulphide is eliminated, and the phenyl isothiocyanate which remains combines, in its turn, with a second molecule of amine, giving a diarylthiourea. 

Attaching an isothiocyanate group to the aromatic ring of U-50488 has been reported to produce the first site-directed alkylating agent to bind irreversibly to kappa receptors in guinea-pig membranes [51]. 

An interesting variation of this quinoxaline synthesis is outlined by the synthesis of sydnoquinoxalines shown in Scheme 103. The starting material is phenylsydnone 288 with an iminophosphorane group in an o-position. With isocyanate or isothiocyanate carbodiimide intermediates 289 are formed by an electrophilic aromatic substitution at the sydnone ring (4 position), the 4-(arylamino)sydno[3,4-a]quinoxalines (290) are obtained (91S745). 

Indian workers described the synthesis of l,3,4-thiadiazolo[3,2-a]-5-triazine-5(//)-thiones (61) by a hetero Diels-Alder reaction between 2-(arylideneamino)-5-ethylthio-l,3,4-thiadiazoles (60) and aromatic isothiocyanates (Equation (2)) <94MI 410-0I>. Thiadiazoles can be reduced with sodium amalgam to the aldehyde thiosemicarbazone while lithium aluminum hydride will reduce mesoionic thiadiazoles all the way to the hydrazine <84CHEC-I(4)545>. 

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