Tryptamines, Carbolines, and Related Compounds: Part Vii. Internuclear Cyclization Onto a Pyridine Ring

Abramovitch, R. A.

doi:10.1139/v60-305

Cited by 22 publications

(4 citation statements)

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“…However, the lack of regioselectivity observed with pyridine ring as a radicophile in an intramolecular addition reaction had also been noticed by Abramovitch in a study examining the viability of 1,4-ipso-substitution processes. 40 Interestingly, the ratio of products corresponding to a-and g-attack in his study correlates well to the value observed in our example.…”

Section: 6-ipso-substitution Versus 17-additionsupporting

confidence: 89%

Synthesis of biaryls via intramolecular free radical ipso-substitution reactions

et al. 2015

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Section: 6-ipso-substitution Versus 17-additionsupporting

confidence: 89%

Synthesis of biaryls via intramolecular free radical ipso-substitution reactions

et al. 2015

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“…T h e mixture of tetrahydro derivatives could be separated by chromatography on a column of alumina, when the 6-carboline derivative was eluted first, followed by the p-compound. The order of elution is similar to that reported by Abramovitch (8) for the separation of mixtures of ind-N-methyl-6-carboline and ind-N-methyl-P-carboline. The cyclization of cyclohexallone 3-pyridylhydrazone was found to give very reproducible yields, thus providing a good route to the 8-carboline ring system.…”

supporting

confidence: 87%

TRYPTAMINES, CARBOLINES, AND RELATED COMPOUNDS: PART X. AN ALTERNATIVE SYNTHESIS, AND THE NITRATION, OF Δ-Carboline

Abramovitch¹,

Adams²

1962

Can. J. Chem.

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6-Carboline, together with 8-carboline, has been synthesized in reasonably good yield by the Fischer cyclization of cyclohexanone 3-pyridylhydrazone followed by dehydrogenation of the separated tetrahydro derivatives. The isomer ratios of products formed in this and similar reactions are discussed. Nitration of 6-carboline gives a mixture of the 6-and 8-nitro derivatives, the latter being the predominant product. The magnitude of the dipole moment of 6-carboline is appreciably higher than that predicted from n~olecular orbital calculations (15).The first unaillbiguous synthesis of 6-carboline'"1) was described in Part VIII of this series (I), in which the cyclizatioil of 3-azido-2-phenylpyridine was reported to give variable )~ields of (I). In order to study the substitution reactioils of this ring system a synthesis giving inore reproducible yields was required. An alternative method of obtaining the 6-carboline ring system was sought and found in the Fischer cyclization of cyclohexailone 3-pyridylhydrazone (11).The Fischer cyclization of pyridylhydrazones has been found by a nuinber of worlters to talte place with greater difficulty than the cyclization of the correspondiilg phenylhydrazones. Perkin and Robinsoil were unable to effect the cyclization of acetone 2-quinolylhydrazone (2), a i d Fargher and Furness (3) and Oltuda and Robisoil (4) obtained similar negative results using a number of 2-pyridylhydrazones. Cleino and Holt prepared 1-methyl-5,6,7,8-tetrahydro-p-carbolii in low ~~i e l d from cyclohexailoile 2-n1ethy1-3-pyridylh)~drazone and zinc chloride (5j. A moderate yield of 5,6,7,8-tetrahydro-a-carboline was obtained by heating cyclohexanone 2-pyridylhydrazone with polyphosphoric acid (4). Ficlten and Kendall have recently examined the cyclizatioil of the pyridylhydrazones of isopropylinethyl ltetone to give the corresponding azaindole derivatives (6). They found that heating with zinc chloride to a relatively high temperature (210-250") was necessary to effect ring closure. I t is interesting to note, as well, that isopropylmetl~yl ltetone 3-pyridylhydrazone was reported by these authors to give exclusively 2,3,3-trimethyl-313-4-azaindole; i.e. cyclization had occurred a t the a-position of the pyridine ring only. Similarly, Taltahashi, Sailtachi, Goto, and Shiinamura (7) obtained ~-chloro-2-inethyl-4-azaindole from acetone 2-chloro-5-pyridylhyclrazone.3-Hydrazinop3~ridine reacted with cyclohexanone to give the required cyclohexanone 3-pyridylhydrazone (11), which was somewhat unstable in air but could be kept for long periods in a closed container in the refrigerator. Cyclization was effected by fusion of (11) with zinc chloride a t 250" and gave a high yield (94%) of a mixture of 6,7,8,9-tetrahydro-6-carboline (111) (63%) and 5,6,7,8-tetrahydro-P-carboline (IV) (37%). The structures of (111) and (IV) were established by dehydrogenation to the corresponding fully aromatic structures. The dehydrogenations were carried out by heating the coinpound with 10% palladiuin-charcoal in boiling me...

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“…10-l8 (9). The copper-catalyzed decoinposition of the diazonium salt of 2-amino-N-methyl-N-3'-pyridylaniline gave a mixture of carbolines (72y0) while the thermal decomposition yielded 47y0 of cyclized products (10). The total yield of cyclized products in the coppercatalyzed reaction was comparable to that obtained (78y0) (11) when N-(3-amino-2-pyridy1)-N-methylaniline was ring-closed to the CY-carboline, i.e.…”

mentioning

confidence: 99%

Aromatic Substitution: Part Ix. On the Mechanism of the Pschorr Cyclization

Abramovitch¹,

Tertzakian²

1965

Can. J. Chem.

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The decomposition of the diazoniuni salt from 3-(0-ami1iobenzoy1)pyridine has been studied under various conditions. A competitive-type cyclization of an equi~nolar ~iiixture of the diazonium salts of 2-aminobenzophenone and 2-arnino-3'-nitrobenzophenone has also been carried out. The results are interpreted in ternis of a radical process in the copper-catalyzed reactions. I t is suggested t h a t the uncatalyzed thermal decompositions in aqueous acid s o l u t i o~~ give rise to a diradical cation interlnediate in equilibriu~n with the aryl cation.

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Tryptamines, Carbolines, and Related Compounds: Part Vii. Internuclear Cyclization Onto a Pyridine Ring

Abstract: not available

Cited by 22 publications

References 1 publication

Synthesis of biaryls via intramolecular free radical ipso-substitution reactions

Synthesis of biaryls via intramolecular free radical ipso-substitution reactions

TRYPTAMINES, CARBOLINES, AND RELATED COMPOUNDS: PART X. AN ALTERNATIVE SYNTHESIS, AND THE NITRATION, OF Δ-Carboline

Aromatic Substitution: Part Ix. On the Mechanism of the Pschorr Cyclization

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