Isothiocyanates reaction with aromatic compounds

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... 

Particularly significant is the extension to the S5mthesis of enantioenriched oxazolidin-2-thiones of the reaction of isothiocyanate 189 with aromatic aldehydes. This reaction is catalysed by Mg(C104) and the asymmetric induction is provided by a pybox ligand <05AG(E)1543>. A different approach to enantioenriched oxazolidin-2-thione was provided by a kinetic resolution of racemic substrate with an organic catalyst. Compound 192 efficiently catalysed the methanolysis of iV-acyl oxazolidinethiones 191 and afforded an efficient kinetic resolution of 191 with an s-factor up to 32 <05JA13502>. 

Alkylation of metal thiocyanates has been known to produce isothiocyanates, and this can be followed by treatment with carbon nucleophiles to give thioamides. Alternatively, metal thiocyanates can be used in the Friedel-Crafts reactions of aromatic compounds. For example, the reactions of aromatic compounds bearing alkoxy groups and heteroaromatic compounds with potassium thiocyanate under acidic conditions are carried out at 30 °C (Eq. 11) [34]. In the reaction a large excess of methanesulfonic acid is used. 

Rebeiro and Khadilkar have investigated the reactions of trichloroalkanes with aromatic compounds. For example, the benzoylation of aromatic compounds in ionic liquids was performed using benzotrichloride, which on aqueous work up gave ketones [77]. Thioamidation of aromatic compounds can be achieved by the reaction of isothiocyanates with aromatic compounds in the presence of chloroaluminate ionic liquids [78],... 

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). 

An exchange reaction is observed in the reaction of aromatic nitroso compounds 72 with isothiocyanates to give azo derivatives 73 and carbonoxy sulflde. ... 

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). 

The CH2 group of co-imidazol-l-yl)acetophenone 1004 is sufficiently activated by the carbonyl and the imidazole group that it readily reacts with aldehydes, aromatic diazonium salts (to form diazo compounds) and acrylonitrile. The reaction of 1004 with phenyl isothiocyanate in the presenceof KOH results in the formation of adduct 1005 that is not isolated but further condensed with phenacyl bromide to afford thienylimidazole 1006 in 87% yield (Scheme 241) <2003SC153>. In the presence of a 2-sulfanyl group 1007, the enolate of ot-imidazolyl acetophenone 1008 no longer reacts with aldehydes or even alkyl halides except for Mel 1009 <200282691 >. 

The chemical reactivity of the cumulenes under discussion ranges from highly reactive species to almost inert compounds. While some cumulenes can only be generated in a matrix at low temperatures, others are indefinitely stable at room temperature. For example, sulfines and sulfenes are only generated in situ, but some cumulenes with bulky substituents are sometimes isolated at room temperature for example, C=C=S was detected in interstellar space by microwave spectroscopy, and its spectrum was later verified by matrix isolation spectroscopy. In contrast, some cumulenes, such as carbon dioxide and carbon disulfide, are often used as solvents in organic reactions or in the extraction of natural products. The reactivity of some center carbon heterocumulenes in nucleophilic reactions is as follows isocyanates > ketenes > carbodiimides > isothiocyanates. However these reactivities do not relate to the reactivities in cycloaddition reactions. Often reactive cumulenes are isolated as their cyclodimers. Aromatic diisocyanates are more reactive than aliphatic diisocyanates in nucleophilic as well as cycloaddition reactions. 

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