Arylamino isocyanates

Die Curtius-Umlagerung von N-substituierten N-Aryl-carbamidsaure-aziden liefert als Pri-marprodukt Arylamino-isocyanate, die durch intramolekulare Cyclisierung 3-Hydroxy-1H-indazole liefern651. 

Arylamino isocyanates undergo an intramolecular cycloaddition reaction. For example, heating of diphenylcarbamoyl azide in xylene generates the diarylamino isocyanate 13, which cyclizes to give 1-phenylindazolone 14... 

The synthesis of 5-aminothiazoles via the reaction of isocyanate derivatives with aminomalononitrile p-toluenesulfonate (AMNT) has been investigated. It was found that AMNT 12 reacted with alkyl and aryl isothiocyanates in l-methyl-2-pyrrolidine (NMP) to furnish 5-amino-2-(alkylamino)-4-cyanothiazoles (13a) and 5-amino-2-(arylamino)-4-cyanothiazoles (13b-c) in 44-81 % yields. " ... 

More recently, the El and electrospray ionization (ESI) mass spectra of 2,5-diaryl- and 2-arylamino-5-aryl-l,3,4-oxadiazoles, as well as their complexes with copper cations, were studied. Under ESI conditions, loss of NH3 and HNCO, from complexes of 2,5-diphenyl-l,3,4-oxadiazole, 2,5-bis(2-pyridyl)-l,3,4-oxadiazole, or 2,5-bis(4-pyridyl)-1,3,4-oxadiazole with copper cation, was observed <2004JMP272>. An unusual elimination of isocyanic acid was found in fragmentation of some protonated 2,5-diaryl derivatives <2002RCM390>. 

When solutions of iminophosphorane 366 in anhydrous DMF are treated with an aromatic isocyanate at room temperature, 2-arylamino-imidazo[2,TA][l,3,4]thiadiazol-5(67/)-ones 135 are isolated (Equation 70) <2004S1067>. 

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). 

A mixture of alkyl azides, substituted phenyl isothiocyanate and aryl or alkyl isocyanate are reported to yield 5-arylamino-l,2,4-thiadiazolin-3-ones (283) via a proposed 1,2,3,4-thiatriazoline (282) (Scheme 64) <84CHEC-I(6)463>. 

Kaugars and Rizzo have found that 5-alkylamino- or 5-arylamino-l,2,3,4-thiatriazoles react with isocyanates to give 3-oxo-A4-l,2,4-thiadiazolin-5-ylureas (65) (79JOC3840). The structures were verified by independent synthesis and by H and I3C NMR spectroscopy. In the presence of triethylamine the exothermic reaction went to completion in a few hours. The reaction may either take place by attack at the amino group to give (63), followed by N2 extrusion to form the reactive dipole (64 equation 31), or the reaction may be initiated by attack at the ring in the 4-position to give an intermediate thiatriazoline, which, as discussed above, reacts with heterocumulenes (see Section 4.28.2.3.l(iii)). As expected, 5-(dialkylamino)thiatriazoles were not found to react with isocyanates. 

In the reaction of the heterocyclic N-substituted iminophosphorane 9 with aryl isocyanates, 2-arylamino-l,2,4-triazolo[5,l-b]quinazolin-9(3H)-ones 10 are formed in 86-94 % yield. ... 

Thus, heating methyl 2-aminonicotinate under reflux for 16 hours with methyl isocyanate in pyridine gave a 76% yield of 3-methylpyrido[2,3-rf]pyrimidine-2,4(l//,3/f)-dione (R1 = H R2 = Me), whereas the method using ethanolic aqueous potassium hydroxide as catalyst88 could not be repeated.83 The cyclization of 2-(arylamino)nicotinic acid methyl esters with various alkyl isocyanates requires 6 days at reflux in xylene with camphorsulfonic acid as catalyst.91,92... 

Starting with acyclic precursors in a one-pot reaction, 2-amino-2-[(4,6-dimethylpyrimidin-2-yl)methylene]pentane-2,4-dione (29) reacts with two molecules of aryl isocyanate to yield the corresponding 3-aryl-7-(arylamino)-4-methyl-8-(4,6-dimethylpyrimidin-2-yl)pyrido[2,3-rfl-pyrimidine-2,5(3//,8 tf)-dione (30).404 40 5... 

Deprotonation of the 4-amino group in 4-(arylamino)nicotinic esters with sodium hydride and subsequent conversion to a urea with allyl isocyanate yields an intermediate urea, whose cyclization furnishes the corresponding l-aryl-3-allylpyrido[4,3-r/jpyrimidine-2,4(l//,3//)-dione 12.498... 

Amino-6-methyl-3-methylthio-l,2,4-triazin-5(2/f)-one (343) reacts with diarylcarbodiimides to form 8-aryl-7-arylamino-3-methyl[l,2,4]triazolo[5,l-c][l,2,4]triazin-4(8//)-ones (344), and the same products are formed from the iminophosphoranes (345) with isocyanates (Scheme 62) <86H(24)3363>. The iminophosphoranes are prepared from the corresponding amines with triphenylphosphine dibromide. 

Synthesis of C-4 unsubstituted l,3,6-triaryl-3,4-dihydropyrimidin-2(lH)-ones 179, through aromatic isocyanates 177 with (l-arylamino-l-phenylpropan-l-ones 178 in refluxing toluene has been achieved (Scheme 68) (08JHC1095). 

However, in the only example we are aware of direct thermolysis of an asymmetric urea [17], mixed ureas containing an arylamino and a diethylamino groups selectively decomposed to the arylisocyanate and diethylamine. Since the reaction is catalysed by acids, it is likely that protonation of the more basic diethylamino nitrogen is the first step of the thermolysis, thus addressing the reaction towards the production of the arylisocyanate. This kind of process may become of much grater importance in the future, since the synthesis of ureas appears to be easier than the one of either isocyanates or carbamates with several catalytic systems. 

Methyl-5-arylamino-l,2,3,4-thiatriazolines 403 react with isocyanates at room temperature in chloroform to give the expected cycloadducts 404, which rearrange to form 4-methyl-5-arylimino-l,2,4-thiadiazolidine-3-ones 405". ... 

A variety of alditol-l-yl substituted heteiocyclic derivatives have been synthesized. The tetiazole derivative (94) was derived riom maltose, and convened into the corresponding 1,3,4-oxadiazoles (95) on acetylation or benzoylation. Reaction of l-arylamino- or 1-alkylamino-l-deoxy-D-arabino-hexuloses with cyanamide gave the imidazole derivatives (96). Fructosazine (97) and deoxyfiructosazine (98) were simultaneously formed by self-condensation of 2-amino-2-deoxy-D-glucose in neutral to basic aqueous solutions, and were shown to have DNA strand breaking activity. Condensation of 2-amino-2-deoxy-D-glucose with aryl isocyanates gave adducts such as (99) that exist in solution as (R,5)-mixtures in which the (R)-fonn predominates. ... 

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