73223-48-0Relevant academic research and scientific papers
Ketene-Ketene interconversion. 6-Carbonylcyclohexa-2,4-dienone-hepta-1,2,4, 6-tetraene-1,7-dione-6-oxocyclohexa-2,4-dienylidene and wolff rearrangement to fulven-6-one
Koch, Rainer,Blanch, Rodney J.,Wentrup, Curt
, p. 6978 - 6986 (2014/08/18)
6-Carbonylcyclohexa-2,4-dienone (1) has been generated by flash vacuum thermolysis (FVT) with Ar-matrix isolation of methyl salicylate (7), 2-phenylbenzo-1,3-dioxan-4-one (8), phthalic peranhydride (9), and benzofuran-2,3-dione (11) and also by matrix photolysis of 9, 11, and 2-diazocyclohepta-4,6-dien-1,3-dione (12). In each case, FVT above 600 °C results in decarbonylation of 1 and Wolff rearrangement to fulven-6-one (13) either concertedly or via open-shell singlet 6-oxocyclohexa-2,4-dienylidene (18). Ketenes 1 and 13 were characterized by IR spectroscopy. Photolysis of matrix-isolated 1 at 254 nm also results in the slow formation of 13. The sequential formation of ketenes 1 and 13 from 7 has also been monitored by FVT-mass spectrometry, and 13 has been trapped with MeOH to afford methyl 1,3-cyclopentadiene-1- and -2-carboxylates 15 and 16. FVT of methyl salicylate-1-13C 7a revealed a deep-seated rearrangement of the 13C-labeled 1a to hepta-1,2,4,6-tetraen-1,7-dione (17a) by means of electrocyclic ring opening followed by a facile 1,5-H shift and recyclization prior to CO-elimination and ring contraction to 13C-labeled 13. The rearrangement mechanism is supported by M06-2X/6-311++G(d,p) calculations, which predict feasible barriers for the FVT rearrangements and confirm the observed labeling pattern in the isolated methyl salicylate 7a/7b and methyl cyclopentadienecarboxylates 20 and 21 resulting from trapping of 13 with MeOH.
DYnamics of the Wolf Rearrangement of Six-Membered Ring o-Diazo Ketones by Laser Flash Photolysis
Tanigaki, Katsumi,Ebbesen, Thomas W.
, p. 4531 - 4536 (2007/10/02)
The Wolff rearrangement of six-membered ring o-diazo ketones, 1-oxo-2-diazo-1,2-dihydronaphthalene (DNQ) and its four 4- and 5-sulfonate analogues, 1-ox-2-diazo-1,2-dihydrobenzene (DBQ), and diazoMeldrum (DM), are studied in solution at room temperature by laser flash photolysis.A precursor to a ketene is observed in most cases.It is assigned to be an oxirene on the basis of reactivity, kinetic results and thermodynamic results.The Wolff rearrangement does not involve a concerted mechanism but a stepwise reaction for these types of diazo ketones.Thermodynamic analyses indicate that the activation barriers for the transformation of the oxiranes into ketenes are very low, typically 10-20 Kj/mol, in godd agreement with theoretical predictions in the literature.The observation of oxirene in solution in nanosecond time scales, and longer, is attributed to the low preexponential factors due to the negative entropy of solvatation.The important role of the solvent is further confirmed in the kinetic analysis of ketene formation in various water-methanol mixtures.
Synthesis of some 1,2-Dihalogenonorbornanes
Krebs, Ernst-Peter,Keese, Reinhart
, p. 2029 - 2041 (2007/10/02)
The synthesis of 1,2exo-dibromo-norbornane as well as the preparation of the configurational isomers of 2-bromo-1-iodo- and 2-chloro-1-iodo-norbornane are described.
