Isothiocyanates dimerization reactions

Dickore and Kuhle have utilized this type of reaction to prove the structure of arylsulfonyl isothiocyanate dimers (CIII). 

Sulfonyl - and alkoxycarbonyl isothiocyanates undergo dimerization reactions across their C=S bonds to give four-membered ring cycloadducts 1. 

Several reactive isothiocyanates undergo dimerization reactions in which one of the isothiocyanates functions as the diene and the other isothiocyanate reacts as the dienophile. These [4-1-2] cycloaddition reactions are very pronounced with heterocyclic isothiocyanates and isothiocyanates having carbonyl, thiocarbonyl and imidoyl substituents. For example, 2-pyridyl isothiocyanate undergoes dimerization to give the triazine derivative 2. ... 

Cycloadditions The [4+2] cycloaddition reactions of carbodiimides with phenyl-carbonyl isocyanate, phenylcarbonyl isothiocyanate and thiocarbamoyl isothiocyanate have been discussed above. In the dimerization reactions the functional carbodiimides react as both the diene and the dienophile. Unsaturated carbodiimides, generated in situ, can be trapped with N=N bond- or C=N bond-containing substrates. 

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... 

A typical cyclization reaction starting from a 3-aminopyrazole is the transformation of 255 <2000BML821 >. This compound was treated first with ethoxycarbonyl isothiocyanate followed by sodium methoxide to yield a cyclic intermediate which was methylated by methyl iodide to give the stable product 256. In the cases of the synthesis of 257 <1995PHA675>, the dimeric 258 <2005JHC975>, the azo-substituted 259 <2001JCM439>, and the diaryl... 

Heterocyclic substituted carbodiimides can undergo dimerization by a [2-1-4] cycloaddition process. For example, di-2-pyridylcarbodimide 194, generated in situ in the reaction of an iminophosphorane with CS2 and an isothiocyanate, affords the cyclodimer 195,... 

Another goitrogenic compound in cabbage is thiocyanate ion (107) which results from breakdown of indolylmethyl isothiocyanate produced from the corresponding glucosinolate, glucobrassicin (97,106,108) (reaction G). The 5-hydroxymethylindole thus produced can dimerize to 3,3 -diindolylmethane or form a complex (ascorbigen) with ascorbic acid (perhaps a novel type of feedback inhibition of ascorbate-dependent... 

In the case of the reaction of 1 with COS the intermediate silathione dimerizes to the dithiadisiletane derivative III. In the reaction of 1 with RNCS the silathione does not dimerize, but it is trapped by the respective isothiocyanate in form of the formal [2+2] cycloaddition product IV. The intermediates Cp 2Si=X (X = O, S) (2) could not be isolated but derivatized by trapping reactions. In the presence of t-butyl methyl ketone the silanone (Cp 2Si=0) reacts in an ene-type reaction [9] to give the addition product 5 the silathione (Cp 2Si=S) is transformed in a first step to an addition product analogous to 5, in a further step this species reacts with 1 in an oxidative addition process to form the final product 4 (see Scheme 2). 

Aminothienopyrimidinones 41 were synthesized by cyclization of vic-cyanothienylureas 42 generated in situ by the reaction of 2-amino-3-cyanothiophenes 30 with isothiocyanates (1985CB4473) or urea (1990MI1). Compound 41 with R3 = H exists predominantly as the tautomeric 4-NH form. The reactions with isothiocyanates are accompanied by dimerization as a side process (1991JPR229). 

Aminoacetophenones (265) when reacted with thiophosgene in a mixture of chloroform, water, and calcium carbonate form the corresponding isothiocyanates (266), but these spontaneously cyclize to afford 4-methylene-3,l-benzoxazine-2-thiones (267) which rearrange under the reaction conditions to yield 4-methylene-3,l-benzothiazin-2-ones (268). These products then slowly dimerize to 4-(3,l-benzothiazine-4-yl)methylene-3,l-benzothiazines (269) (Scheme 51) <9UHC1091>. 

In addition to dimerization and their reaction with transition metals, NHCs are also known to react quantitatively with various organic electrophiles, such as azides [13] and isothiocyanates [14]. Such types of NHC-electrophile reactions... 

Dithiocarboxylic acids (118) can be converted into 1,3-dithietans (119) by acid chlorides,iodine, HCl, DCCI, or upon standing for a long time, and they are formally thioketen dimers. The cycloaddition of two C=S groups yields thioketen dimers and (120) from methyl isothiocyanate. Derivatives (121) are prepared by the reaction of dithiocarboxylic acids (118) with phosgene. ... 

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