Thermal elimination reactions of nitrogen and sulphur heterocycles

Grigg, R.; Hayes, R. Andrew; Jackson, John L.

doi:10.1039/c29690001167

Cited by 27 publications

(6 citation statements)

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“…Some of the well-known tandem reactions of this type reported in the literature include cycloaddition of a variety of alkynes to pyrimidines resulting in cycloadducts that spontaneously extrudes nitrile to form pyridines [1]. A similar nitrile expulsion has been reported with oxazoles [2]. Pyrone undergoes cycloaddition with alkene/alkyne to form a bicyclic lactone that spontaneously extrudes CO 2 to form molecules with cyclohexadiene/ benzene unit.…”

Section: Introductionmentioning

confidence: 74%

Tandem Cycloaddition-Cycloreversion of 2-pyrone and 1,4-oxazinone with Acetylene - A DFT Insight

Kalpana¹,

Akilandeswari²,

Venuvanalingam³

2021

IJPC

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Reaction of either 2-pyrone or 1,4-oxazinone with acetylene follows the sequence of cycloadditioncycloreversion through concerted mechanism. Transition states for both cycloaddition and cycloreversion pathways have been obtained in both the cases by modelling the reactions at B3LYP/6-31g (d) level. Cycloreversion is faster than cycloaddition in the case of 2-pyrone due to the enhancement of aromaticity resulting the product as benzene. In contrast, oxazinone has rapid cycloaddition. It is ascribed to the presence of nitrogen in this system. Removal of either CO 2 or HCN is plausible in this mechanism to complete the reaction. Even though two pathways are feasible for cycloreversion, CO 2 extrusion is more preferable than HCN elimination. In these two studied molecules, there is an enhancement of aromaticity up to transition states like any other pericyclic reaction and further it diminishes during cycloaddition. Further, aromaticity is specifically augmented in cycloreversion phase during CO 2 elimination resulting to yield pyridine whereas competitive HCN elimination results in the formation of 2-pyrone which is less facile. In both the molecules the aromatic enhancement of the cycloreversion is substantiated through the study of magnetic susceptibility of the ring fragment along the reaction coordinate. Further the study also reveals the effect of halogen substituted at different carbons of 2-pyrone ring.

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Section: Introductionmentioning

confidence: 74%

Tandem Cycloaddition-Cycloreversion of 2-pyrone and 1,4-oxazinone with Acetylene - A DFT Insight

Kalpana¹,

Akilandeswari²,

Venuvanalingam³

2021

IJPC

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“…When a p- xylene solution of 1,2-dithiete 1 was refluxed for 8 h, the thiophene 10 was obtained in 31% yield (Scheme ). Therefore, the formation of thiophene 10 in the reaction of 1,2-dithiete 1 with N- phenylmaleimide or maleic anhydride can be explained as the result of reaction of 1,2-dithiete 1 with ethane-1,2-dithione 13 because the desulfurization of the cycloadduct 14 probably forms 1,4-dithiin derivative followed by rearrangement and subsequent desulfurization , to give thiophene 10 . The calculated energy difference between the LUMO of 13 and the HOMO of 1 is 8.9 eV, and that between the π of 13 and the LUMO of 1 is 12.4 eV.…”

Section: Resultsmentioning

confidence: 99%

Reaction of 1,2-Dithiete with Alkenes and Alkynes: Experimental and Theoretical Study

1999

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Reactions of 3,4-bis(methoxycarbonyl)-1,2-dithiete (1) with various alkenes or alkynes formed 2,3-dihydro-1,4-dithiins or thiophenes, respectively. The reactions with alkenes were stereospecific, which indicates the concerted reaction between 1,2-bis(methoxycarbonyl)ethane-1,2-dithione (13), the valence isomer of the 1,2-dithiete, and the dienophiles. Theoretical study confirmed the reactions of 13 with alkenes and alkynes are of reverse electron demand hetero Diels-Alder type. The MO calculations showed the 1,2-dithiete 1 was 5.8 kcal mol -1 more stable than the corresponding ethane-1,2-dithione 13, and the tautomerization energy between the 1,2-dithiete and the ethane-1,2-dithione was also calculated to be 28.5 kcal mol -1 from the 1,2-dithiete, which suggests the tautomerization from 1,2-dithiete 1 to ethane-1,2-dithione 13 is possible at least at high temperature. Reaction of 3,4,7,8-tetrakis(methoxycarbonyl)-1,2,5,6-tetrathiocin (2) or (Z,Z,Z,Z)-3, 4,7,8,11,12,15,16-octakis-(methoxycarbonyl)-1,2,5,6,9,10,13,14-octathiacyclohexadeca-3,7,11,15-tetraene (3) with ethyl vinyl ether also formed the 2,3-dihydro-1,4-dithiin derivative, which is the same compound obtained by the reaction of 1,2-dithiete 1 with the ether. 1,2,5,6-Tetrathiocin 2 and 16-membered cyclic compound 3 also reacted with diphenylacetylene to give the thiophene derivative.

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“…Found: C, 83.5; H, 4.5; N, 12.0. 9-(l-Naphthyl)anthracene (7).-A solution of 0.90 g (0.0025 mol) of 5-azido-5-(l-naphthyl)-5H-dibenzo[o,d]cycloheptene (3a) in 20 ml of o-dichlorobenzene was heated at reflux until gas evolution stopped (5 min). The evolved gas was collected over water.…”

Section: Methodsmentioning

confidence: 99%

“…The naphthyl-substituted azide 3a is readily prepared and thermally decomposed smoothly in refluxing o-dichlorobenzene with evolution of nitrogen to yield the nitrogen-free product 9-(1-naphthyl) anthracene (7) in good yield (88%). If the gas evolved is passed through water, a solution is obtained from which, after addition of silver nitrate, silver cyanide can be precipitated in 75% yield.…”

mentioning

confidence: 99%

Thermal decomposition of some 5-substituted 5-azido-5H-dibenzo[a,d]cycloheptenes. A transannular nitrene addition

Looker¹

1971

J. Org. Chem.

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Thermal decomposition of 5-(l-naphthyl)-5-azido-5ff-dibenzo [a,d]cyclohepten.e yields 9-(1 -naphthyl)anthracene, probably via an unstable azasemibulvalene. When the substituent group is smaller than naphthyl, ring contraction is not favored. When the naphthyl ring of the azide has a 4-dimethylamino substituent, the latter is readily replaced by nucleophiles, providing a novel method for the preparation of 9-(4-substituted 1-naphthyl)anthracenes.The preparation of one azasemibulvalene system, 1, has been reported.1 The sandwich structure2 3proposed

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Thermal elimination reactions of nitrogen and sulphur heterocycles

Cited by 27 publications

References 0 publications

Tandem Cycloaddition-Cycloreversion of 2-pyrone and 1,4-oxazinone with Acetylene - A DFT Insight

Tandem Cycloaddition-Cycloreversion of 2-pyrone and 1,4-oxazinone with Acetylene - A DFT Insight

Reaction of 1,2-Dithiete with Alkenes and Alkynes: Experimental and Theoretical Study

Thermal decomposition of some 5-substituted 5-azido-5H-dibenzo[a,d]cycloheptenes. A transannular nitrene addition

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