Oxoisoindolium hexachloroantimonate 1a was reacted with different nitriles to afford 2-azoniaallene salts. These underwent cyclization on heating, furnishing tetracyclic compounds 2a, b. Oxoisoindolo[2,1-a]quinazolinium hexachloroantimonate 3 reacted with p-toluidine to afford the corresponding salt 4. This was neutralized with sodium carbonate to give the corresponding free base 5. Isoindolo[2,1-a]quinazoline derivative 6 was prepared by treatment of 3 with benzohydrazide in dichloroethane. Reaction of the extremely sensitive salt of oxoisoindolium 1 with aminothiazole derivative 7 afforded the formal salts of 2-azoniaallene 8. Neutralization of these afforded the corresponding free base 9. The structures of the synthesized compounds were confirmed by IR, 1H NMR, 13C NMR, and mass spectroscopy. The free base compounds were screened for antimicrobial activity.

Substituted 2-azoniaallene salts 1 are strong bifunctional electrophiles, undergo cyclization reactions furnish many series of heterocyclic compounds, where reacted with p-tolyl urea, phenyl thiourea and thiosemicarbazone derivatives to afford triazinium salts, and converted to corresponding free bases 3, 5, 7 under treatment with Na2CO3. While triazole derivatives 8 and 9 were obtained by the reaction 2-azoniaallene salts 1 with benzohydrazide and phenyl hydrazine, respectively. Benzoxazinium salts 10 and 11 were acquired when asymmetric 2-azoniaallene salt reacted in (1:1) ratio with p-cresol and 3-methyl-1-phenyl-5-pyrazolone, respectively. The reaction of 2-azoniaallene salt with malononitrile furnished the primidinium salt 12 which underwent neutralization with Na2CO3 followed by heterocyclization with hydrazine hydrate afforded the bicyclic compound 3-aminopyrazolo[3,4-d]pyrimidine 14, which is highly reactive for nucleophilic addition to phenyl isothiocyanate to furnish thiourea derivative 15. Moreover, 14 undergo condensation with aldehydes to give imine derivatives 16a,b. All free base compounds were screened for their antimicrobial activities.

Chloro(phenyl)carbenium hexachloroantimonate salts react with isocyanates to afford either isoindolium (1) or benzoxazinium salts (2). Addition of one equivalent of alcohol to 2 led, after hydrolysis with aq. NaOH, to the formation of benzoxazin-2-ones 3. Treatment with a large excess of alcohol transformed the salts 1 and 2 to the corresponding isoindol-1-ones 11 and the isocyanates 5, respectively. Reaction of 5 with primary amines furnished the urea derivatives 6 in good yield. The biological activity of 6a - o against HIV-1 was determined.

A series of substituted thieno[2,3- d ]pyrimidines was synthesized starting from ethyl-2-amino-4-isopropylthiophene-3-carboxlate. Reaction of 2-hydrazino-5-isopropyl-thieno[2,3- d ]pyrimidin-4(3H)-one and its 3-methyl analogue with different reagents afforded thieno[2,3- d ]triazolo[4,3- a ]pyrimidines and thieno[3,2- e ]triazolo[4,3- a ]pyrimidines, beside open chain derivatives.

Triazolo-thieno[3,2-e]pyrimidines obtained by cyclisation of 4-hydrazino-2-(methylthio)thieno[2,3-d]pyrimidine with formic acid, acetic acid, cyanogen bromide and carbon disulfide, and by oxidation of the derived aldehyde hydrazones, are found to be the triazolo[4,3-c] isomers. These [4,3-c] compounds resist isomerisation in acid, but they undergo Dimroth rearrangement to the [1,5-c] isomers under basic conditions. The crystal structure of one such rearranged product, 5-methoxy-8,9,10,11-tetrahydro[1]benzothieno[3,2-e][1,2,4]triazolo[1,5-c]pyrimidine (13b) was confirmed by X-ray analysis.

3-Chloro-2-substituted-1-oxoisoindolium hexachloroantimonate (1) reacted with water, ethanol and dimethyl-cyanamide to give the corresponding phthalimide derivatives 2, 3 and 4 respectively. Reaction of 1a with nitriles afforded the intermediate 2-azoniaallene salts 5 which underwent cyclisation reaction upon heating to furnish the ellipticine analogues 6. The biological activities of 6a–e against HIV-1 and HBV viruses were determined.

Treating 2-chloro-4-(4-chlorophenyl)-6-methylbenzo[d]-3,1-oxazinium hexachloroantimonate (1) with one equivalent of alcohol or mercaptane led, after hydrolysis with aq. NaOH, to the formation of 4,4-disubstituted-1,4-dihydro-2H-6-methyl-3,1-benzoxazin-2-ones (3). Large excess addition of alcohol afforded either 4'-chloro-2-isocyanato-5-methylbenzophenone disubstitutedketal (4) or N-{2[(4-chlorophenyl)dialkoxymethyl]-4-methylphenyl} alkylcarbamate (5). Reaction of 4 with primary amines furnished 1-{2-[(4-chlorophenyl)dialkoxymethyl] -4-methylphenyl}-3-substituted urea (6).

Reaction of 3-hydrazinophenanthro [9, 10-e] [1, 2, 4] triazine (1) with aliphatic and aromatic aldehydes as well as monosaccharides gave the corresponding hydrazones 2a-g. The D-glucose analogue exists in the cyclic pyranosyl structure 5. Acetylation and partial acetylation of the sugar hydrazones were carried out. Cyclization of a number of hydrazones including the partially acetylated sugar hydrazones by thionyl chloride gave regioselectively the respective angular isomer 1-substituted phenanthro [9, 10-e] [1, 2, 4] triazino [3, 4- and not the linear isomer. The cyclization of 1 with acetic acid, however, gave regioselectively the linear isomer 19. The structural assignments were based on a model study whereby the angular 16a was found to be different from the linear isomer 19a obtained by the condensation of 4, 5-diamino-3-methyl-1, 2, 4-triazole with 9, 10-phenanthraquinone. Periodate oxidation of 2d gave 20 whose reaction with 1 gave 21.

Aryl-, and vinyltrichloromethanes 1 are transformed with antimony pentachloride to alpha,alpha-dichlorocarbenium salts 2, which react with sulfinylamines 3 to afford nitrilium salts 4 in good yields. In contrast to this preparatively useful reaction, the reaction of alpha-monochlorocarbenium ions 8 (obtained from diaryldichloromethanes 7) with sulfinylamines 3 affords mixtures of iminium salts 10, isoindolium salts 13, and 2-azoniaallene salts 14.

1,3-Dichloro-2-azoniaallene hexachloroantimonates (1) reacted with H2S to give 1,2,4-dithiazolium salts 2. With hydrazines 1,2,4-triazolium salts (3, 4) were formed. 1,3-Dimethylurea, respectively 1,3-dimethylthiourea or ethyl allophanate, reacted with 1 to afford 2-oxo- or 2-thioxo-1,3,5-triazinium salts (5–7). With diphenylmethaneimines imino substituted 2-azoniaallene salts 8 were produced. From chloroacetonitrile dichloropyrimidines 9, and from the tricyanomethyl anion a hexatriene 10 and a triazine 11 could be prepared. The 1,5-dichloro substituted 2-azoniaallene salts 12 reacted as bifunctional electrophiles with nucleophiles such as benzophenone hydrazone or anilines, to furnish 1,3,5-triazinium salts 14. Against benzohydrazide the allene 12j behaved as trivalent electrophile giving the bicyclic 1,3,5-oxadiazinium salt 13j, the constitution of which has been secured by a crystal structural analysis. The vinyl-2-azoniaallene salt 1i cyclized on heating to the 1,3-thiazinium salts 16, 17. From 17 the triazinium salts 18 were prepared with alcohols.

Aryl- and alkylhydrazones 1 of alkyl ketones and propanal are transformed to 1-chloroalkylazo compounds 2 with tert-butyl hypochlorite. Compounds 2 react with antimony(V) chloride or aluminum(III) chloride to give 1-aza-2-azoniaallene salts 3 as reactive intermediates, which are intercepted as 3H-1,2,4-triazolium salts 5 with nitriles. In most cases these salts rearrange spontaneously to form the corresponding 1H-triazolium salts 6. Benzophenone arylhydrazone 1x reacts with tert-butyl hypochlorite and antimony(V) chloride to furnish the 1-aryl-3-phenylindazolium salt 7. An X-ray diffraction analysis of a 1H-1,2,4-triazolium salt [6,7,8,9- tetrahydro-2-methyl-3-(2,4,6-trichlorophenyl)-5H-[1,2,4] triazolo [5,1-a]azepinium hexachloroantimonate (6n)] is reported.

Trichlormethanes 4 react with two equivalents of n-alkyl isocyanates R2-NCO in the presence of SbCl5 to furnish the 2,2-dichloro-5,6-dihydro-6-oxo-2H-1,3,5-oxadiazinium salts (9). The structure of these heterocycles is confirmed by an X-ray analysis of 9d (R1 = ClC = CCl2, R2 = Et). p-Tolyl isocyanate is Friedel-Crafts alkylated by 4b in the presence of SbCl5. Subsequent ring closure affords the quinolinium salt 13, which is hydrolyzed to give inter alia the quinolone 16.

The multifunctional electrophilic chloro-substituted 2-azoniaallene salts 3-5 react with bifunctional nucleophiles under cyclization to furnish heterocycles. Preparations of the 1,2,3,4-tetrahydro-1,3-dimethyl-2,4-dioxopyrimido[4,5-d]pyrimidines 7 a,b, 10 a,b, 14,17 a,b, and the 5,6,7,8-tetrahydro-6,8-dimethyl-5,7-dioxopyrimido[5,4-e]-1,3-oxazin-1-ium salts 9a,b, 15, first representatives of a new ring system, are reported. Furthermore, the 2,3-dihydro-1,3-dimethyl-4-(methylthio)-2-oxo-1,3,5-triazinium salts 11 d,e, 13, and 3-(dimethylamino)-4,5-dihydro-5-oxo-2-(2,4,6-trichlorophenyl)-1H-1,2,4-triazol-2-ium hexachloroantimonate (12) are obtained.

α-Chlorocarbenium ions, 9, stabilized by allylic resonance, react with nitriles, 10, to give chloro substituted 2-azoniaallene salts, 12. The cation 12k abstracts chloride from the counterion SbCl6− to furnish the chloroimine 13k together with SbCl5. The hexachloroantimonates 12 can be transformed into unpolar chlorides, 13b,1, and 17, with ammonium chlorides. Compounds 13 and 17 are hydrolyzed to give N-acyl imidoyl chlorides, 14a,b, respectively the allophanate 18. Electron-rich nitriles insert into the CCl bond of the 2-azoniaallene salts 12 to afford imidoyl chlorides, 151-p,16.

N-Arylnitrilium salts 1 react with isocyanates 2 to give salts 3 of 4(3H)-quinazolinones 4, from which compounds 4 can be obtained with base. A metathesis of an isocyanate with a nitrilium salt is reported.

Quinolinium salts 3 are obtained from the reaction of N-arylnitrilium salts 1 with acetylenes 2. With aqueous base the salts 3 are transformed into the corresponding quinolines 4.

The nitrile N-oxide 4 undergoes a reversible cycloaddition to the carbonyl group of the 1-oxa-3-azoniabutatriene salts 3a–c to give the geminal dioxy substituted 2-azoniaallene salts 5a–c. Azibenzil 7 and 3a,d afford the 2-azoniaallene salts 8a,d. With the nitrone 11 the cumulene 3d reacts to yield the open-chain addition product 12. The salt 3a reacts with two equivalents of diazofluorene to give the β-lactamium salt 13, which can be hydrolyzed to afford the N-formyl-β-lactam 15. X-ray structural analyses of 5b and 8d confirm the proposed constitutions.1

The N‐silylimines (II) react with the chlorocarbenium salts (I) to form the 2‐azoniaallene salts (III).

AbstractThe N‐silylimines (II) react with the chlorocarbenium salts (I) to form the 2‐azoniaallene salts (III).

Reaction of ammonium thiocyanate (II) with the α‐chlorocarbenium salts (I) yields the 1‐thia‐3‐azabutatrienium salts (III), whereas potassium cyanate (IV) produces the 1‐oxa‐3‐azabutatrienium salts (V).