67093-47-4Relevant academic research and scientific papers
Ketene recognizes 1,3-dienes in their s-Cis forms through [4 ± 2] (Diels-Alder) and [2 ± 2] (Staudinger) reactions. An innovation of ketene chemistry
Machiguchi, Takahisa,Hasegawa, Toshio,Ishiwata, Akihiro,Terashima, Shiro,Yamabe, Shinichi,Minato, Tsutomu
, p. 4771 - 4786 (2007/10/03)
The mechanism of ketene-diene reactions has been studied both experimentally and theoretically. Careful experiments of the reactions of diphenylketene (1) with cyclic (s-cis) 1,3-dienes [cyclopentadiene (2) and cyclohexa-1,3-diene (3)] lead to the first direct detection of the Diels- Alder cycloadducts (10 and 11) by low-temperature NMR spectroscopy. The initially formed cycloadducts are converted to the final Staudinger products, cyclobutanones (6 and 7), by [3,3] sigmatropic (Claisen) rearrangements. In contrast, ketene 1 reacts with open-chain 1,3-dienes [2,3-dimethyl-1,3- butadiene (4) and 1-methoxy-1,3-butadiene (5)] to afford initially both the Staudinger-type (8, 9) and Diels-Alder-type cycloadducts (12, 13). The Staudinger cycloadducts (8, 9) are converted eventually to Diels-Alder products (12, 13) by the retro-Claisen rearrangement. Thus, ketene recognizes dienes in cycloadditions as ketenophiles different from olefins. [4 + 2] and [2 + 2] cycloadducts are generated and can be intermediates or products flexibly according to diene structures.
Reactions of diphenylketene and methylphenylketene with some cis-cyclohexa-3,5-diene-1,2-diol derivatives
Roberts, Stanley M.,Sutton, Peter W.,Wright, Lorraine
, p. 1157 - 1165 (2007/10/03)
The reaction of the dienes 1-5 with diphenylketene to give the [2 + 2]-adducts 6-10 and the [4 + 2]-adducts 11-15, respectively, has been found to occur by an ionic mechanism involving the zwitterion 16. The reactions of the dienes 2 and 3 with methylphenylketene (and also cyclohexa-1,3-diene with diphenylketene) proceed in a similar fashion. The enol ether 13 was converted into the polyoxygenated cyclohexane derivatives 33, 35 and 38.
