Synthesis and reactions of [1,2,4]Triazolo[4,3-a]pyridinium-3-aminides and [1,2,4]triazolo[4,3-a]pyrimidinium-3-aminides

Evaluation of the scope and mechanism of a new type of heterocyclic rearrangement

Brian C. Bishop, Hugh Marley, Kevin J. McCullough, Peter N. Preston, S. H B Wright

Research output: Contribution to journalArticle

Abstract

1,2,4-Triazolo[4,3-a]pyridinium betaines 6a, b have been prepared by treating 2-pyridyl-4-phenylthio-semicarbazides 4a, b with dicyclohexylcarbodiimide, and related compounds 6c-f have been prepared through the intermediate S-methyl thiosemicarbazides 5c-f. Reaction of the pyrimidin-2-yl thiosemicarbazide derivatives 8a-c with dicyclohexylcarbodiimide (DCC) gave the 1,2,4-triazolo-[4,3-a]pyrimidinium betaines 7a-c, but attempted thermal cyclization of the free bases derived from methiodides 8j-o gave a series of enamines 11. The structure of one such enamine 11a was elucidated by degradation with 2 mol dm-3 HCl which afforded a mixture of the amine 9 and the ketone 10. Treatment of the thiosemicarbazide 8d with dicyclohexylcarbodiimide gave the pyridinium betaine 14a, and a related compound 14b was prepared by reaction of the salt 12b with diazabicyclo[5.4.0]undec-7- ene (DBU). The crystal and molecular structure of the maleate salt of 14b was determined by X-ray crystallography. It was established that the betaine 14a could be converted into an enamine derivative 11a by heating it in toluene.

Original languageEnglish
Pages (from-to)705-714
Number of pages10
JournalJournal of the Chemical Society, Perkin Transactions 1
Issue number6
Publication statusPublished - 1993

Fingerprint

Betaine
Dicyclohexylcarbodiimide
Semicarbazides
Salts
Derivatives
X ray crystallography
Cyclization
Toluene
Ketones
Molecular structure
Amines
Crystal structure
Heating
Degradation
thiosemicarbazide

Cite this

@article{4e2338e667c949a38a68436da829d7cb,
title = "Synthesis and reactions of [1,2,4]Triazolo[4,3-a]pyridinium-3-aminides and [1,2,4]triazolo[4,3-a]pyrimidinium-3-aminides: Evaluation of the scope and mechanism of a new type of heterocyclic rearrangement",
abstract = "1,2,4-Triazolo[4,3-a]pyridinium betaines 6a, b have been prepared by treating 2-pyridyl-4-phenylthio-semicarbazides 4a, b with dicyclohexylcarbodiimide, and related compounds 6c-f have been prepared through the intermediate S-methyl thiosemicarbazides 5c-f. Reaction of the pyrimidin-2-yl thiosemicarbazide derivatives 8a-c with dicyclohexylcarbodiimide (DCC) gave the 1,2,4-triazolo-[4,3-a]pyrimidinium betaines 7a-c, but attempted thermal cyclization of the free bases derived from methiodides 8j-o gave a series of enamines 11. The structure of one such enamine 11a was elucidated by degradation with 2 mol dm-3 HCl which afforded a mixture of the amine 9 and the ketone 10. Treatment of the thiosemicarbazide 8d with dicyclohexylcarbodiimide gave the pyridinium betaine 14a, and a related compound 14b was prepared by reaction of the salt 12b with diazabicyclo[5.4.0]undec-7- ene (DBU). The crystal and molecular structure of the maleate salt of 14b was determined by X-ray crystallography. It was established that the betaine 14a could be converted into an enamine derivative 11a by heating it in toluene.",
author = "Bishop, {Brian C.} and Hugh Marley and McCullough, {Kevin J.} and Preston, {Peter N.} and Wright, {S. H B}",
year = "1993",
language = "English",
pages = "705--714",
journal = "Journal of the Chemical Society, Perkin Transactions 1",
issn = "1472-7781",
number = "6",

}

Synthesis and reactions of [1,2,4]Triazolo[4,3-a]pyridinium-3-aminides and [1,2,4]triazolo[4,3-a]pyrimidinium-3-aminides : Evaluation of the scope and mechanism of a new type of heterocyclic rearrangement. / Bishop, Brian C.; Marley, Hugh; McCullough, Kevin J.; Preston, Peter N.; Wright, S. H B.

In: Journal of the Chemical Society, Perkin Transactions 1, No. 6, 1993, p. 705-714.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Synthesis and reactions of [1,2,4]Triazolo[4,3-a]pyridinium-3-aminides and [1,2,4]triazolo[4,3-a]pyrimidinium-3-aminides

T2 - Evaluation of the scope and mechanism of a new type of heterocyclic rearrangement

AU - Bishop, Brian C.

AU - Marley, Hugh

AU - McCullough, Kevin J.

AU - Preston, Peter N.

AU - Wright, S. H B

PY - 1993

Y1 - 1993

N2 - 1,2,4-Triazolo[4,3-a]pyridinium betaines 6a, b have been prepared by treating 2-pyridyl-4-phenylthio-semicarbazides 4a, b with dicyclohexylcarbodiimide, and related compounds 6c-f have been prepared through the intermediate S-methyl thiosemicarbazides 5c-f. Reaction of the pyrimidin-2-yl thiosemicarbazide derivatives 8a-c with dicyclohexylcarbodiimide (DCC) gave the 1,2,4-triazolo-[4,3-a]pyrimidinium betaines 7a-c, but attempted thermal cyclization of the free bases derived from methiodides 8j-o gave a series of enamines 11. The structure of one such enamine 11a was elucidated by degradation with 2 mol dm-3 HCl which afforded a mixture of the amine 9 and the ketone 10. Treatment of the thiosemicarbazide 8d with dicyclohexylcarbodiimide gave the pyridinium betaine 14a, and a related compound 14b was prepared by reaction of the salt 12b with diazabicyclo[5.4.0]undec-7- ene (DBU). The crystal and molecular structure of the maleate salt of 14b was determined by X-ray crystallography. It was established that the betaine 14a could be converted into an enamine derivative 11a by heating it in toluene.

AB - 1,2,4-Triazolo[4,3-a]pyridinium betaines 6a, b have been prepared by treating 2-pyridyl-4-phenylthio-semicarbazides 4a, b with dicyclohexylcarbodiimide, and related compounds 6c-f have been prepared through the intermediate S-methyl thiosemicarbazides 5c-f. Reaction of the pyrimidin-2-yl thiosemicarbazide derivatives 8a-c with dicyclohexylcarbodiimide (DCC) gave the 1,2,4-triazolo-[4,3-a]pyrimidinium betaines 7a-c, but attempted thermal cyclization of the free bases derived from methiodides 8j-o gave a series of enamines 11. The structure of one such enamine 11a was elucidated by degradation with 2 mol dm-3 HCl which afforded a mixture of the amine 9 and the ketone 10. Treatment of the thiosemicarbazide 8d with dicyclohexylcarbodiimide gave the pyridinium betaine 14a, and a related compound 14b was prepared by reaction of the salt 12b with diazabicyclo[5.4.0]undec-7- ene (DBU). The crystal and molecular structure of the maleate salt of 14b was determined by X-ray crystallography. It was established that the betaine 14a could be converted into an enamine derivative 11a by heating it in toluene.

UR - http://www.scopus.com/inward/record.url?scp=37049088759&partnerID=8YFLogxK

M3 - Article

SP - 705

EP - 714

JO - Journal of the Chemical Society, Perkin Transactions 1

JF - Journal of the Chemical Society, Perkin Transactions 1

SN - 1472-7781

IS - 6

ER -