The gas-phase thermal and photochemical decomposition of heterocyclic compounds containing nitrogen, oxygen, or sulfur

Braslavsky, Silvia E.; Heicklen, Julian

doi:10.1021/cr60308a002

Cited by 76 publications

(19 citation statements)

References 111 publications

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“…[7] These species are thought to arise via rearrangement of B in a process analogous to that responsible for the scrambling of substituents in furans, thiophenes, and pyrroles. [20] Further support for this hypothesis comes from recent studies by Hughes et al, [21] according to which 3-vinylcyclopropenes readily rearrange to [Cp*Rh(h 4 -C 4 R 4 )] complexes in the presence of [{RhCl(C 2 H 4 ) 2 } 2 ] and Cp*Li.…”

Section: Resultsmentioning

confidence: 92%

By What Mechanisms Are Metal Cyclobutadiene Complexes Formed from Alkynes?

Veiros

Dazinger

Kirchner

et al. 2004

Chemistry A European J

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The mechanism of formation of an eta4-cyclobutadiene complex from a metallacycle, generated by oxidative coupling of two acetylenes with the fragments CpRuCl, [CpRu(PH3)]+, CpCo, and CpRh, was investigated by means of DFT/B3LYP calculations. Two distinct pathways can be envisaged. 1) A multistep reaction, which can be denoted the Vollhardt mechanism, proceeding via a cyclopropenyl carbene and a tetrahedrane-type intermediate. 2) A one-step transformation involving the formation of a third M-C bond with rearrangement of the metallacyclic ring. Although path 2 is definitely favored over path 1, both pathways are energetically prohibitive unless substituents are present on the acetylene. For the CpRuCl system with HC triple bond CR the barrier varies with R in the series H approximately Ph>Me>>SiMe3. On going from H to SiMe3, the barrier for path 2 drops from 41.1 to 26.8 kcal mol(-1). This latter value is already reachable, in agreement with experiment. Whereas the reaction mechanisms involving the fragments CpCo, CpRh, and CpRuCl are very similar (but not identical owing to the additional ligand in CpRuCl), those of [CpRu(PH3)]+ reveal a modification with serious consequences. In both paths 1 and 2, the originally planar metallacycle experiences first a bending distortion induced by the sigma-donor strength of P (in contrast to Cl), which compensates the loss of electrons from the ring brought about by bending. The bent metallacycle is already electronically asymmetric and thus the further course of the reaction is facilitated.

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Section: Resultsmentioning

confidence: 92%

By What Mechanisms Are Metal Cyclobutadiene Complexes Formed from Alkynes?

Veiros

Dazinger

Kirchner

et al. 2004

Chemistry A European J

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“…Generation of free radicals seems to be favoured by the reaction conditions (1000 o C; quartz apparatus). Phenyl radicals can generate biphenyl (4) and benzene (identified in traces), whereas fission (c) affords benzonitrile (2). On the other hand, in the diradical 16 an usual 1,2-phenyl migration could lead to the intermediate occurrence of phenylketene 17.…”

Section: Resultsmentioning

confidence: 99%

“…The thermal behaviour of a large variety of heterocyclic compounds has been investigated in connection with mechanistic and/or synthetic studies [1][2][3]. Though flash-vacuum pyrolyses (FVP) of a few substituted and annulated isoxazoles [4][5][6] as well as of different isoxazolones [7][8][9] were investigated (revealing the preferential fission of the N-O bond, and the extrusion of CO 2 , respectively) reports on the gas-phase chemistry of oxazoles are very scarce.…”

Section: Introductionmentioning

confidence: 99%

Flash Vacuum Pyrolysis of 2,5-Diphenyloxazole

et al. 2000

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FVP of the title oxazole (1) at 1000 o C and 0.5 mm Hg afforded a complex reaction mixture containing benzonitrile, phenylacetonitrile, biphenyl, diphenylmethane, fluorene, o-benzylbenzonitrile (major product, 22%), phenanthrene, anthracene, 9,10-anthraquinone, 2-phenylindole and 3-phenylindole. A radical and carbene mechanism was suggested in order to rationalize the formation of the reaction products.

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“…Irradiation of ethyleneimine (341,342) with light of short wavelength in the gas phase has been carried out directly and with sensitization (343)(344)(345)(346)(347)(348)(349). Photolysis products found were hydrogen, nitrogen, ethylene, ammonium, saturated hydrocarbons (methane, ethane, propane, n-butane), and the dimer of the ethyleneimino radical.…”

Section: Thermal and Photochemical Reactionsmentioning

confidence: 99%