85153-65-7Relevant articles and documents
Vinylketene-acylallene rearrangement
Bibas, Hervé,Wong, Ming Wah,Wentrup, Curt
, p. 9582 - 9583 (1995)
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The vinylketene-acylallene rearrangement: Theory and experiment
Bibas, Herve,Wong, Ming Wah,Wentrup, Curt
, p. 237 - 248 (2007/10/03)
Alkoxyviniyketenes 4 are generated by flash vacuum thermolysis (FVT) or photolysis of 3-alkoxycyclobutenones 3. The thermal interconversion of 4 and allene carboxylic acid esters 5 under FVT conditions is demonstrated by Ar matrix FTIR spectroscopy. In addition, ethoxyvinylketene 4b undergoes thermal elimination of ethene with formation of s-cis-and s-trans-acetylketene (8). An analogous aminovinylketene-to-allenecarboxymide conversion is observed on FVT of 3-dimethylaminocyclobutenone 3e. A facile 1,3-chlorine migration in 2,3-butadienoyl chloride (5d) is also reported. Consistent with the experimental observations, 1,3-methoxy, 1,3-chloro, and 1,3-dimethylamino migrations in vinylketene are calculated (G2(MP2,SVP) level) to have moderate barriers of 169, 157, and 129 kJmol-1, respectively, significantly less than the corresponding 1,3-H shift barrier (273 kJ mol-1). The stabilization of the four-center transition structures is rationalized in terms of the donor acceptor interaction between the lone pair electrons of the migrating donor substituent and the vacant central carbon p-orbital of the ketene LUMO. The predicted migratory aptitude in the series of substituted vinylketenes. R-C(=CH2)-CH=C=O, is in the order N(CH3)2>SCH3>SH>Cl>NH2>OCH3>OH>F>H>CH3, and correlates well with the electron-donating ability of the R group.