Joachim G. Schantl

Expedient Synthesis of N-Substituted 2-Aminothiazoles

Abstract The reaction of α-halo ketones 1 with potassium thiocyanate and amines 3 offers the advantage of an efficient one-pot synthesis of the title compounds 4 from readily available starting materials.

1-phenylazo-1-alkenes

Aliphatic aldehyde phenylhydrazones 1 were converted into 1-phenylazo-1-alkenes 3bd either by the reaction with I2 and pyridine followed by base induced 1,4-elimination of pyridine. HI (Method A), or via N-(4-methylbenzenesulfonyl)-N-phenylhydrazones 7 which undergo 1,4-elimination of p-toluenesulfinic acid upon treatment with KOt-Bu (Method B). Both procedures yield mixtures of configurational isomers of the phenylazo-alkenes EE- and EZ- 3b-3e; Method B is giving rise to a kinetically controlled isomer mixture (EZ-3 predominant), which equilibrates to the thermodynamic ratio (EE-3 predominant) as afforded by Method A.

Addition products of hydrazine derivatives to azo-alkenes - III. α-phenylhydrazino-phenylhydrazones☆

Abstract The addition of phenylhydrazine to phenylazo-alkenes 4 yields α-(1-phenylhydrazino)-phenylhydrazones 1 . The reaction of phenylhydrazine with α-halogenated carbonyl compounds 5 affords either 1 or the isomeric α-(2-phenylhydrazino)-phenylhydrazones 2 . Structures 1 and 2 (>N-NH2 and-NH-NH- groups, respectively) can be differentiated by 1H NMR in DMSO-D6 solution. Possible pathways of the reactions leading to either 1 or 2 are discussed. Compounds 1 are found to be precursors of phenylosazones 6 .

Ring opening of [1,2,3]triazolo[1,5-a]pyrazinium salts: Synthesis and some transformations of a novel type of 2-aza-1,3-butadienes

Abstract The synthesis of 1,3-disubstituted [1,2,3]triazolo[1,5-a]pyrazinium salts 6 and subsequent ring opening induced by the reaction with pyrrolidine provides a facile access to 4-(1-pyrrolidino)-1-([1,2,3]triazol-5-yl)-2-aza-1,3-butadienes 7, a new type of 2-aza-1,3-butadienes. Compounds 7 proved to be suitable starting materials for further ring formation reactions.

N-Arenesulfonyl-N-phenylhydrazones

Abstract The phenylhydrazones of aliphatic aldehydes and ketones, and those of benzaldehyde and benzophenone react with various sulfonylchlorides in the presence of a suitable base to give the title compounds; examples of their synthetic use are given.

Oxidation ofN-Aminophthalimide in the Presence of Conjugated Azoalkenes: Azimines, Azoaziridines, and [1,2,3]Triazoles

The oxidation of N-aminophthalimide (1) with lead tetraacetate in the presence of the phenylazoalkenes 2 afforded 2-phenylazo-1-(N-phthalimido)aziridines 3 or 2-phenyl[1,2,3]triazoles 7, as well as phthalimide (4). The reaction of 2-phenylazo-1-propene (2d) produced 5-methyl-2-phenyl[1,2,3]triazole (7d) and N-[2-(phenylhydrazono)propylideneamino]phthalimide (8d). The cyclic azoalkene 3,3,5-trimethyl-3H-pyrazole (11) gave a mixture of (Z)-3,3,5-trimethyl-1-[N-(phthalimido)amino]-3H-pyrazol-1-ium-2N-ide [(Z)-12] together with the regioisomers (E)- and (Z)-3,3,5-trimethyl-1-[N-(phthalimido)amino]-3H-pyrazol-2-ium-1N-ides [(E)- and (Z)-13].

A new synthesis of thes-triazolo[1,5-a]pyridine ring system

SummaryA novel and efficient synthesis ofs-triazolo[1,5-a]pyridines was elaborated by reacting 1,2-diaminopyridinium salts with aldehydes.ZusammenfassungEine neue und effektive Synthese vons-Triazolo[1,5-a]pyridinen durch die Reaktion von 1,2-Diaminopyridiniumsalzen mit Aldehyden wurde ausgearbeitet.

α-(1-phenylhydrazino)-alkanone phenylhydrazones: The reaction with carbonyl compounds

Abstract The unsymmetrically disubstituted hydrazines 1 were condensed with carbonyl compounds. Some of the expected condensation products were isolated, but some were formed as unstable intermediates which underwent 1,4-elimination: The phenylhydrazone of the carbonyl compound used was obtained, together with the corresponding phenylazo-alkene 11 or alternatively, the 1,4-addition product of a different protic nucleophile to 11.

Novel synthesis of N,N'-bis (α-isocyanato alkyl)diazenes

Abstract The conversion of aliphatic ketazines 1 with cyanic acid into the “criss cross” cycloadducts, the triazolo-triazolediones 2 , followed by oxidative ring opening provides an efficient synthetic route to the title compounds 4 .

Geminale Azo- und Heteroelement-Funktionen, IV: O- und N-Funktionelle Arylazo-diphenylmethyl-Derivate

The reaction of benzophenone arylhydrazones1 with bromine in pyridine solution yields 1-(arylazo-diphenylmethyl)-pyridinium bromides2 and pyridine · HBr. The inseparable salt mixtures upon treatment with a series of O- and N-nucleophiles undergo displacement of the pyridinium moiety of2 affording the title compounds3–14.