Ketene N,N-acetals ( I ) and ketene 0,N-acetals (2) containing hydrogen in the 2-position afford P-substitution products when treated with compounds such as isocyanates and isothiocyanates that contain an electrophilic double bond system[l~zl. However, azosulfones (3) [31 and N-sulfonylimines (7) [41 react with ketene N,N-acetals ( I ) by cycloaddition, affording the hitherto unknown 1,2-dihydr...

Ketene (CH2=C=O) has been postulated as a key intermediate for the first olefin production in zeolite-catalyzed chemistry of methanol-to-olefins (MTO) and syngas-to-olefins (STO) processes. The reaction mechanism remains elusive, because short-lived ethenone ketene its derivatives are difficult to detect, which is further complicated by low expected concentration. We report on experimental dete...

Ab initio surface-hopping dynamics calculations have been performed to simulate the intramolecular excited state hydrogen transfer dynamics of ortho-nitrobenzaldehyde (o-NBA) in the gas phase from the electronic S(1) excited state. Upon UV excitation, the hydrogen is transferred from the aldehyde substituent to the nitro group, generating o-nitrosobenzoic acid through a ketene intermediate. The...

The potential energy surface for the intramolecular excited state hydrogen transfer (IESHT) in ortho-phthalaldehyde (OPA), which generates an enol ketene, has been studied with ab initio calculations (MS-CASPT2//CASSCF). The goal of our study is to establish the mechanistic factors that make the primary phototautomerization step irreversible. Similar to what we recently described for ortho-nitr...

Dibenzoylketene 5 undergoes degenerate 1,3-shifts of the phenyl group between acyl and ketene carbon atoms, thus interconverting it with 6 and 7. This 1,3-shift takes place in the gas phase under flash vacuum thermolysis (FVT) conditions, but not in solution at 110-145 degrees C. Imidoyl(benzoyl)ketene 13 undergoes degenerate 1,3-shift of the phenyl group on FVT, thus interconverting it with 14...

The reactivity of quinoneimines towards ketene and diphenylketene was examined. N-Phenylbenzoquinoneirnines (I), (2) and also N-phenylnaphthoquinoneimine react with ketene to give the spiro-adducts (5), (7) and (1 1) respectively. These adducts were stable even after prolonged heating in high boiling solvent. Reaction of the above imines with diphenylketene also afforded 13- lactam spiro-a...

Intensive studies have been carried out on the rotational spectra of various isotopic species of ketene, H2C = C = 0 , since 1950 [ 1 6 ] . The centrifugal distortion analysis of ketene [3, 4 ] , together with information from additional infrared data [3, 5 ] , enabled Mallinson and Nemes [6] to reevaluate the molecular force field for ketene. Recently, microwave investigations on the higher ho...

The photo-isomerization of o-acetylbenzaldehyde (oABA) in acetonitrile was studied by femto- and nanosecond transient absorption spectroscopy. Spectroscopic signatures are assigned with the aid of TD-DFT, TD-CAM-DFT and DFT-MRCI computations. The isomerization yields a lactone, 3-methylphthalide (3MP), with a quantum yield of 0.3 (30%). As evidenced by femtosecond stimulated Raman spectroscopy ...

Highly enantioselective protonation of α-halo and alkoxy carboxylic acid-derived ketene disilyl acetals is achieved by using P-spiro chiral diaminodioxaphosphonium barfate as a Brønsted acid catalyst, where the enantiofacial discrimination by the catalyst mainly stems from the recognition of the electronic difference between two substituents on the ketene disilyl acetal.

A molecular beam Fourier transform microwave spectrometer, designed for the study of chemical reactions within electrical discharges, is described in detail. Applications include the production of carbonyl fluoride, ketene, acetic acid, and difluorocarbene. For the production of carbonyl fluoride and ketene with 1,1-difluoroethylene and carbon dioxide as precursor molecules a reaction path via ...