Pyridinium N-imides

The first fully unsaturated monocyclic 1,3-diazepines (61) have been prepared only recently. In the thermolysis of li/-l,2-diazepines it has been found that cleavage of the N—N bond in (58) is favoured by electron release from groups in the 4- and 6-positions so that 1,3-diazepines (61) are then formed rather than pyridinium N -imides (59) (79JOC2683, 80CC444). It has also been shown (81H(16)137) that 1,3-diazepines are produced by the thermolysis of 1,2-diazepine photoproducts of type (54). 

Trlaza-Compounds. Pyridinium N-imide combines with trifluoroacetonitrile to form a mixture of the triazolopyridine (521) and another compound, which is thought... 

This is very similar to the above method of conversion of pyridinium Ar-imides to 1,2-diazepines. Here the tetrahydrocarbolines <1996CHEC-II(9)113> or the tetrahydroisoquinolines <1984CHEC(7)593> are N-substituted and N-aminated with O-sulfonyl hydroxylamine derivatives followed by treatment with base to give the corresponding 1,2-diazepines. 

Some time ago the Streith ring-expansion of pyridinium AT-imides was extended to the synthesis of lf/-l,2-benzodiazepines from quinoline N-imides. The full report has now appeared of the further extension of this valuable synthetic route to the preparation of the following previously unknown 1,2-diazepines, annelated to heteroaromatic rings pyrido[3,2-c]-,pyrido[2,3-c]-,thieno[2,3-c]-, thieno[3,2-c]-, and furo[2,3-c]-l//-l,2-diazepines e.g., (61) from (59), presumably via (60)." A similar attempt to prepare pyrrolodiazepines was not successful. These 1//-tautomers were converted into the 3//-l,2-diazepines by reduction with lithium aluminium hydride and then dehydrogenation with 4-phenyl-l,2,4-triazoline-3,5-dione. ... 

There are two routes to [l,2,4]triazolo[l,5-a]pyridines from N-aminopyridinium salts. In one, Ar-(2-pyridyl)hydrazides (34) are converted by MSH (mesitylsulfonylhydroxylamine) to AZ-aminopyridinium salts, and these cyclize on heating, giving 1-aminotriazolopyridinium salts C35).4 In the other, AZ-aminopyridinium salts are treated with AZ-ethoxycarbonylacet-imidate to give pyridinium ylides (36), which cyclize on heating, giving mixtures of triazolopyridines and imidazopyridines.47,48... 

Aromatic tkio orthoesters are successfully converted into trifluoromethyl arenes by treatment with a pyridinium poiyhydrogen fluoride-iV-halo imide reagent. The reactions are conducted at -30 to -20 °C, and the nature of N-halo imide is critical both l,3-dibromo-5,5-dimethylhydantoin and A-bromosuccin-imide give similar yields of trifluoromethyl compounds [5] (equation 7)... 

The synthetic uses of the acid-promoted decomposition of a-diazoketones have been reviewed.A comparative study of methods for the synthesis of optically pure N-protected a-aminoaldehydes concludes that borane-THF is the reagent of choice for the reduction of N-protected amino-acids to the amino-alcohol without racemization, and that pyridinium dichromate is satisfactory for the subsequent oxidation to the aldehyde. Since the reaction between amines and a-haloketones is sometimes a poor method for the preparation of a-alkylaminoketones, the far less basic imidates have been developed as effective nucleophilic components in this reaction [equation (51)]. a-Aminoketones can also be prepared via Wittig rearrangement of iminoethers [equation (52)], ° or by a-aminomethylation of aldehydes [equation (53)]. ... 

Acetates of organic bases Diethylamine acetate Pyridinium salt Tetramethylammonium acetate, Tetraethyl-ammonium-Piperidinium acetate Isoxazolium salts Trialkyloxonium salt Amidinium salts Ketenimines Diazomethane K-methyldiazotate Hexamethylenetetramine Azo compounds Triazenes p-Nitrobenzene-diazonium sulfate Sulfanilic acid, diazotized HCONH2, CHsCONH2 Dimethylacylamines HCON(CHs)2, CHsCON(CHs)2 Dimethylformaldehyde dineopentyl acetate 1-Benzyl-1,4 -dihydro nicotinamide N,N -Diethylnicotin-amide C0(NH2)2, (CHs)2NCON(CHs)2 Phenyl isocyanate Carbodiimides Dicyclohexylcarbodi-imide, Di-p-tolyl-Antipyrine... 

Picon, S., Zaparudia, A, and Al-Mourabit, A. (2009) N-Pyridinium imidates as new sources of 2-aminoimidazole and imidazoline derivatives. Tetrahedron Lett.. 50, 6826-6829. 

BMIM][C1] (l-n-butyl-3-methylimidayolium bis (trifluorometh-ylsulfonyl) imide chloride) and [BPy][Cl] (l-n-butyl-3-pyridinium chloride) may have similar activity to the pesticide parquet. 

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