Skraup Reaction Research Articles

ChemInform Abstract: Synthesis of Heterocyclic Compounds by the Skraup Reaction of Amino‐9H‐ xanthen‐9‐ones.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Synthesis of Heterocyclic Compounds by the Skraup Reaction of Amino-9H-xanthen-9-ones

The Skraup reaction of amino-9H-xanthen-9-ones was conducted in the presence of glycerol, fuming sulfuric acid, nitrobenzene, iron (II) sulfate and boric acid. 1-Amino-9H-xanthen-9-one gave 12H-[1]benzopyrano[2,3-h]quinolin-12-one. 2- And 3-amino-9H-xanthen-9-ones gave angular-type products, 12H-[1]-benzopyrano[3,2-f]quinolin-12-one and 7H-[1]benzopyrano[3,2-g]quinolin-7-one respectively, without linear-type products. 4-Amino-9H-xanthen-9-one gave 7H-[1]benzopyrano[3,2-h]quinolin-7-one

Synthesis of New Heterocyclic Compounds by the Skraup Reaction of Amino-9H-thioxanthen-9-ones.

The Skraup reaction of amino-9H-thioxanthen-9-ones was conducted in the presence of glycerol, fuming sulfuric acid, nitrobenzone, iron(II) sulfate and boric acid. 1-Amino-9H-thioxanthen-9-one (1) gave 12H-[1]benzothiopyrano[2, 3-h]quinolin-12-one (5). 2-Amino-(2) and 3-amino-9H-thioxanthen-9-ones (3) gave angular-type products, 12H-[1]benzothiopyrano[3, 2-f]quinolin-12-one (6) and 7H-[1]benzothiopyrano[2, 3-f]quinolin-7-one (8), but did not give linear-type products. 4-Amino-9H-thioxanthen-9-one (4) gave 7H-[1]benzothiopyrano[3, 2-h]quinolin-7-one(10).

ChemInform Abstract: Improved Synthesis of Quinaldines by the Skraup Reaction.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Improved synthesis of quinaldines by the skraup reaction

AbstractA series of substituted quinaldines was synthesized with much improved yields from the reaction of croton‐aldehyde and the corresponding anilines using either p‐chloranil or 2,3‐dichloro‐1,4‐naphthoquinone as the oxidant.

Synthesis of pyrido[2,3,4-kl]acridines a building block for the synthesis of pyridoacridine alkaloids

Two new syntheses have been developed for the preparation of substituted pyrido[2,3,4-kl]acridines. The first synthesis involves a Skraup reaction and a nitrene insertion whereas the second includes a new pyridine ring synthesis starting from a 1-amino group on acridine and taking advantage of the active 9-position of the latter heterocycle.

Isomeric ellipticines. Part 1. Synthesis of two linear isomers of the antitumour alkaloid ellipticine

Two linear isomers of the parent 5,11-dimethyl-6H-pyrido[4,3-b]carbazole ellipticine 1a, belonging to the 6H- and 10H-pyridocarbazoles series and their methoxylated derivatives, have been synthesized by three different methods using the Skraup reaction and the Fischer–Borsche cyclization. One of these (method A) afforded an angular monomethyl-7H-pyridocarbazole 9 instead of the expected linear 6H-isomer 8a on cyclisation of 5,8-dimethyl-6-hydrazinoquinoline 21 with cyclo-hexanone via the Fischer–Borsche indole synthesis. The two other methods (B and C) afforded the desired linear isomers 7 and 8 when the Skraup reaction was performed with aminocarbazoles 26 or with tetrahydroaminocarbazoles 17 and 27 respectively, followed by aromatization of the A ring. Oxidized species were isolated after the aromatization step in method C and were tentatively assigned structures 30–33.

Formation of quinolines from 2‐phenylbenzopyrylium chloride

AbstractThe quinolines 5a–e are prepared by thermal treatment of 2‐phenylbenzopyrylium chloride (4) with aromatic amines. The substitution pattern of the products shows that an unusual Skraup synthesis has taken place.

ChemInform Abstract: The Skraup Reaction of 3,4‐Dihaloanilines.

AbstractSulfo‐mix variation of the Skraup reaction of the 3,4‐dihaloanilines (I) with glycerol (II) leads to the formation of mixtures of the 5,6‐(III) and 6,7‐dihaloquinolines (IV).

ChemInform Abstract: Synthesis and Crystal Structure of Naphtho(2,1‐b)(1,5)naphthyridine.

Abstract2‐Aminobenzo(f)quinoline (I) and glycerol (II) undergo modified Skraup reaction to produce naphtho(2,1‐b)(1,5)naphthyridine (III).

ChemInform Abstract: An N → N′‐Benzyl Migration During the Formation of Some (Trifluoromethyl)imidazo(4,5‐h)quinolines.

AbstractThe 7‐amino‐8‐alkylaminoquinolines (VI) are synthesized via a Skraup reaction or photolysis of the azide (VII).

Synthesis and Crystal Structure of Naphtho[2,1-b][1,5]naphthyridine

A modified Skraup reaction was carried out on 2-aminobenzo-[f] quinoline, in the presence of sulfo-mix, using ferrous sulfate and boric acid. This reaction gave the linear type product, naphtho-[2,1-b] [1,5] naphthyridine but not the angular type. Its crystal structure was determined by X-ray analysis

The Skraup Reaction of 3,4-Dihydroanilines

Six 3,4-dihaloanilines were converted by the sulfo-mix variation of the Skraup reaction to mixtures of 5,6- and 6,7-dihaloquinolines, 2 and 3 respectively. Inductive effects were the dominant influence on the course of cyclization: the more highly electron-withdrawing the substituents of 1, the greater was the proportion of 3. Steric effects were absent

The Infrared Spectra of the First Transition Series Metal(II) Bis(Aquo) Complexes Of 8-Hydroxyquinoline

Abstract The infrared spectra (700–100 cm−1) of the complexes [M(ox)2(H2O)2] (ox = 8-hydroxyquinolinate anion, M = Mn, Fe, Co, Ni, Cu, Zn) are discussed. For the purposes of assignment of the metal ligand modes, deuterated 8-hydroxyquinoline-d 7 was prepared by the Skraup synthesis and the spectra of the deuterated complexes were compared with those of the unlabelled species. Furthermore, [64Zn(ox)2(H2O)2] and [68Zn(ox)2(H2O)2] were prepared by reaction of 64ZnSO4 and 68ZnSO4 with 8-hydroxyquinoline and the effects of metal isotope labelling on the spectra were examined and compared with earlier isotopic data on the nickel and zinc complexes.

2,5-Dimethyl-4-(p-aminobenzyl)pyridine in the synthesis of substituted quinolines, pyridoindazoles, and isoquinolinoquinolines

2,5-Dimethyl-4-pyridyl(6-quinolyl)methane was obtained from 2,5-dimethyl-4-(p-aminobenzyl)pyridine via the Skraup reaction. The product was nitrated to 2,5-dimethyl-4-pyridyl (5-nitro-6-quinolyl)methane, which was reduced to 2,5-dimethyl-4-pyridyl (5-amino-6-quinolyl)methane. It was established that the diazo compound formed from this amino derivative is converted to 1H,3-(2,5-dimethyl-4-pyridyl)-pyrido [2,3-g]indazole as a result of intramolecular cyclization. 9-Methyliso-quinolino [7,6-f]quinoline was obtained by catalytic dehydrocyclization of 2,5-dimethyl-4-pyridyl (6-quinolyl)methane. 2,5-Dimethyl-4-pyridyl(5-nitro-6-quinolyl)methane has chemochromic properties.

Synthesis and bromination of 8-methylquinoline-5-carboxylic acid

8-Methylquinoline-5-carboxylic acid was obtained by the Skraup reaction from 3-amino-p-toluic acid or by hydrolysis of 5-cyano-8-methylquinoline. The latter was synthesized by the Rosenmund-von Braun reaction from 5-bromo-8-methylquinoline, which was obtained by bromination of 8-methylquinoline in the presence of silver sulfate. Bromination in the side chain of 8-methylquinoline-5-carboxylic acid and its nitrile was studied.

A general and practicable synthesis of polycyclic heteroaromatic compounds. Part 1. Use of a putative quinolone-quinone-methide in the synthesis of polycyclic heteroaromatic compounds

A general and straightforward new synthesis of polycyclic heteroaromatic compounds has been developed. In the synthesis a putative quinolone-quinone-methide is generated in the presence of an aniline. The ensuing reaction results in a polycyclic heteroaromatic product. In the most useful approach, a hemiacetal (25) is prepared in one step from the parent quinolone and this is heated in the presence of an aromatic amine to produce the polycyclic heteroaromatic compound in good yield. The regiospecificity of the reaction is the opposite to that expected in the Skraup synthesis with respect to the quinone-methide component. With respect to the aniline component, however, regiospecificity is the same as in the Skraup synthesis.

Synthesis of 5H[l]benzopyrano[3,4‐b]pyridin‐5‐one and its derivatives

Abstract3‐Aminocoumarin undergoes the Skraup reaction to give a new ring system, 5H[l]benzo‐pyrano[3,4‐b]pyridin‐5‐one (IVa). When 3‐aminocoumarin was condensed with the ethoxy methylene derivatives of active methylene compounds, ethyl acetoacetate, and dimethyl acetylenedicarboxylate, the intermediates Vla‐VIf were formed which on thermal cyclizations afforded other derivatives of 5H[l ]benzopyrano[3,4‐b]pyridin‐5‐one (IVb‐IVf). The nitration of IVa gave IVg.

Synthesis and nitration of 7-alkylquinolines

The Skraup synthesis with m-ethylaniline has been shown to give a mixture of 7-ethylquinoline (75%) and 5-ethylquinoline (25%). Pure 7-ethylquinoline has been isolated as a solid. Nitration of 7-methyl- and 7-ethylquinolines gives only the 8-nitro derivatives; the minor products from the nitration of impure samples of 7-alkylquinolines arise from the 5-alkyl- contaminants. 5-Methylquinoline is nitrated at the 6- and 8-positions.

Synthetic studies of the antitumor antibiotic streptonigrin. I. Synthesis of the A‐B ring portion of streptonigrin

AbstractBromination of 6‐methoxy‐5,8‐quinolinedione gave the 7‐bromo derivative in quantitative yield. Treatment of the bromo compound with sodium azide followed by hydrogenation yielded 7‐amino‐6‐methoxy‐5,8‐quinolinedione, the A‐B ring portion of the antitumor antibiotic strep tonigrin. The corresponding 2‐methyl homolog was prepared in a similar manner from 6‐methoxy‐2‐methyl‐8‐nitroquinoline, which in turn, was obtained by a Skraup synthesis from 2‐nitro‐anisidine and crotonaldehyde.