3-Acylamino-l-aryl

Anilinocarbonyl-methyl)-l,2,4-oxadiazole gehen bei Basen-Einwirkung intramolekulare Aminierung unter Bildung des Pyrazol-Rings (3-Acylamino-l-aryl-5-hydroxy-lH-pyr-... 

Acylamino- 437, 652 l-Acyl-5-amino- 445 3-Acylamino-l-aryl-5-hydroxy- 535... 

A later investigation focused on the reduction of ketones of the type anri-3-amino- or anti-3-acylamino-l-aryl-2-methyl-3-phenylpropanone with lithium aluminum hydride in tetrahydro-furan78. Most of the experiments led to the. yr/7,a/Jf/-product, the best selectivities being obtained when R2 was hydrogen (d.r. up to 95 5). Modest selectivities in favor of the alternative stereoisomer were obtained when R2 was an aroyl group. 

Oxazoles.—Formation. ci)-Diazoacetophenone reacts with benzonitrile in the presence of trifluoromethanesulphonic acid to give 2,5-diphenyloxazole (514). Bi-, ter-, and quater-oxazoles have been synthesized from a-metallated isocyanides thus lithiobenzyl isocyanide (PhCHLiNC) and dimethyl oxazole-3,4-dicarboxylate afford compound (515). Stable methylene-oxazolines (516 R = Me or Ph) are obtained by heating the iminesHN=C(Ph)OCHRC=CH. The fluorinated oxazoline (518) results from the action of benzonitrile on the oxiran (517), and also from the reaction of bis(trifluoromethyl)carbene with the benzoylimine (CF3)2C=NCOPh/ Treatment of 2-acylamino-l-aryl-alkan-l-ols (519) under the conditions of the Pictet-Gams reaction, i.e. with phosphorus pentoxide in boiling toluene or xylene, results in cis- and trans-2-oxazolines (520), rather than isoquinolines, as claimed previously. The spiro-oxazolines (521 R = Me or Ph) are formed when the lithiated di-isocyanide CN—CH2CH2CHLi—NC is treated with acetone or benzophenone, respec-tively. ... 

Silyl-substituted diazoketones 29 cycloadd with aryl isocyanates to form 1,2,3-triazoles 194 (252) (Scheme 8.44). This reaction, which resembles the formation of 5-hydroxy-l,2,3-triazoles 190 in Scheme 8.43, has no analogy with other diazocarbonyl compounds. The beneficial effect of the silyl group in 29 can be seen from the fact that related diazomethyl-ketones do not react with phenyl isocyanate at 70 °C (252). Although the exact mechanistic details are unknown, one can speculate that the 2-siloxy-1-diazo-1-alkene isomer 30 [rather than 29 (see Section 8.1)] is involved in the cycloaddition step. With acyl isocyanates, diazoketones 29 cycloadd to give 5-acylamino-l,2,3-thiadiazoles 195 by addition across the C=S bond (252), in analogy with the behavior of diazomethyl-ketones and diazoacetates (5). 

Acylamino-6-aryl-3-oxo-2,3,4,5-tetrahydro-l,2,4-triazine reagieren mit Phosphoroxichlorid zu 4H-<1,3,4-Oxadiazolo-[2,3-c]-l,2,4-triazinen>426. 

Azahypoxanthines of type 116 were obtained via an annulation reaction by heating 5-acylamino-4-carboxamido-l, 2,3-triazole with excess hexamethyldisilazane (HMDS) in xylene (95FA257). 3-Aryl-l,2,3-triazolo [4,5-[Pg.104]

Examples include the synthesis of 3-amino-l,2,4-oxadiazoles starting from 3-acylamino-5-methyl-l,2,4-oxadiazole <2002H811> and 2-aryl-l,2,3-triazoles from l,2,4-oxadiazole-3-ketone arylhydrazones <1999T12885, 2006JOC5616>. Oximes, hydrazones, formamidines, and thioureas of the furazan series also undergo base-catalyzed mononuclear rearrangements <2004RCB1121>. Nucleophilic attack at N(3) takes place in the benzofuroxan series. For example, reaction with secondary amines leads to o-nitroarylhydrazines (Scheme 55). 

Acylamino-l,3,4-thiadiazoles have been reduced with lithium aluminium hydride to the corresponding 2-alkylamino derivatives. 2-Amino-5-aryl-l,3,4-thiadiazoles have been found to undergo the Mannich reaction with a variety of methylene compounds. ... 

Bis-[2-acylamino-l-alkenyl]- 325 Bis-[a-anilinocarbonyl-bcnzyl]- 326 Bis-[2-anilino-l-cyan-l-alkenyl]- 333 Bis-[2-anilino-l-cyan-2-phenyl-ethenyl]- 363 Bis-[2-ani ino-l-cyan-l-propenyl]- 363 Bis-[l-aryl-5-itnidazolyl]- 344 Bis-[l,3-benzothiazol-2-yl]- 947, 1000 Bis-[l,3-benzothiazol-2-ylamino-thiocarbonyl]-1004... 

Several reactions of 2-amino- and 2-acylamino-l,3,4-selenadiazoles have been reported. Thus, alkylation of the potassium salt of 180 with methyl and ethyl iodide gave the acylimine 182. The latter upon hydrolysis formed 183.94 Reaction of 179 with alkyl or aryl isothiocyanates resulted in the formation of thioureas (184), while sulfonyl chlorides gave the disulfonyl derivatives 185. Diazotization and coupling reactions of 179 are also... 

Examples of this rearrangement that involve hydrazone as well as hy-drazide side-chain units have been reported, Some arylhydrazones of 5-substituted 3-aroyl-l,2,4-oxadiazoles (43) (see Table II) rearrange by heating at their melting point, or by refluxing with bases or acids, to 4-acylamino-2,5-di-aryl-1,2,3-triazoles (44) 41 44... 

Aminoethyl)-l,2,4-oxadiazoles (606 R = alkyl or aryl) readily isomerize to 3-acylamino-2-pyrazolines (607) on heating. Treatment of the salt (608) with triethylamine yields the transient ylide (609), which decomposes to methyl-phenylcarbodi-imide (610). 2,3-Diphenyl-l,2,4-oxadiazolin-5-one (611) rearranges photochemically to a mixture of the oxadiazolinones (612) and (613) pyrolysis gives 2-phenylbenzimidazole with extrusion of carbon dioxide. The oxadiazole (614) rearranges thermally to the indazole (615). ... 

A particular case of a photochemical strategy towards functionalized benzimidazoles regards the synthesis of 2-acylamino derivatives 70, which can be obtained from irradiations in methanol of 3-(o-amino)phenyl-l,2,4-oxadiazoles 68. In this reaction, a photolytic cleavage of the ring O—N bond, followed by migration of the aryl substituent, leads to the carbodiimide intermediate 69, a precursor of the benzimidazole nucleus (Scheme 12.20) [47]. 

Both the H chemical shifts and NOE data suggest that chloro-A -sulfanes and sulfonium salts 24 and 25 having an o-MeO, o-Cl, or o-Me substituent on the aryl ring assume a skew conformation, whereas the aryl ring in compounds without an ortV o-substituent can rotate practically freely about the S-C(l ) axis. H and N NMR examinations of diaryl(acylamino)(chloro)-A -sulfanes 24a-e showed that they exist only in CDCI3 and dimethyl sulfoxide-t4 (DMSO- 6) solvents (Equation 3), whereas in MeOD complete ionic dissociation takes place, leading to the sulfonium chloride (see Table 5) <2001J(P2)339>. 

Bei der Umsetzung von C-Aryl-N-(l-cyan-alkyl)-nitronen mit Thiocarbonsauren erfolgt auBer der Schwefelung und Cyclisierung uber die Cyan-Gruppe eine zusatzliche Acylierung. Es bilden sich 5-Acylamino-1,3-thiazole661 z.B. ... 

Amino-1,2,4-triazoles (50) or their derivatives are usually starting material for the synthesis. They are readily available and already contain the exocyclic N-N bond required for heteroaromatic A-imines. 4-Amino-1,2,4-triazoles can be quaternized by alkyl halides or tosylates at the N-l atom to give the salt 52.79-82 (Scheme 5) The orientation of quatemization is proved by the reactions in Scheme 6 for the example of the quaternary acylamino salts 52. Quaternary salts of the type 52 can also be prepared by reaction of 1,3,4-oxadiazolium salts (51)83 with aryl hydrazines84 and from aryl hydrazine hydrohalides and orthoesters.86 With alkali, the 1-alkyl-s-triazole-4-imines8(7-82 86 can be obtained in the normal manner from these salts (Scheme 5). The free A-imines are all stable except the A-unsubstituted compound itself.87 Recently, other structures were tentatively reported 88 for the deprotonation products of analogous quaternary salts (52) with hydrazine. 

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