21083-33-0Relevant articles and documents
Photolysis of a benzyne precursor studied by time-resolved FTIR spectroscopy
Torres-Alacan, Joel
, p. 1151 - 1156 (2016)
The 266 nm laser flash photolysis of phtaloyl peroxide (2) in liquid acetonitrile solution at room temperature has been investigated. Upon 266 nm laser irradiation, 2 is effectively photodecarboxylated leading to the formation of o-benzyne (1) and two equivalents of CO2, yet a small fraction of photolyzed 2 follows a different pathway leading to 6-oxocyclohexa-2,4-dienylideneketene (3) and one equivalent of CO2. Compound 3 is kinetically reactive and reacts in the microsecond time scale following a first-order kinetic law. The presence of 1 in the photolysis experiment is confirmed by trapping experiments with methyl 1-methylpyrrole-2-carboxylate (6). The Diels-Alder reaction between 1 and 6 occurs under the selected experimental conditions on a time scale shorter than 100 ms.
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.
6-oxocyclohexa-2,4-dienylideneketene: A highly reactive α-oxoketene
Liu, Regina C.-Y.,Lusztyk, Janusz,McAllister, Michael A.,Tidwell, Thomas T.,Wagner, Brian D.
, p. 6247 - 6251 (2007/10/03)
The title ketene 2 has been generated by laser flash photolysis and observed in solution for the first time, using time-resolved infrared spectroscopy. The kinetics of the reactivity of 2 with H2O, MeOH, and Et2NH with relative reactivities of 1.0, 2.0, and 73 have been measured. These are the first direct measurements of the reactivities of a ketene with these different nucleophiles under the same conditions. Ab initio molecular orbital calculations indicate the hydration occurs by in-plane attack of the H2O molecule on the ketenyl carbonyl through a pseudopericyclic transition state with assistance by coordination to the keto-carbonyl.
