Direct observation of .alpha.-oxo ketenes formed from 1,3-dioxin-4-ones and the enols of .beta.-keto esters
摘要:
The enol forms of beta-keto esters thermolyze to alcohols and alpha-oxo ketenes, which are characterized by low-temperature IR spectroscopy and on warming regenerate the beta-hydroxy-alpha,beta-unsaturated esters. The matrix isolated s-Z and s-E forms of alpha-oxo ketenes are characterized and photochemically converted into other conformers or sites. Matrix photolysis of 2,2,6-trimethyl-1,3-dioxin-4-one gives the s-Z acetylketene initially. Alpha-Oxo ketenes polymerize in the cold and dimerize only at elevated temperatures.
FREIERMUTH, BEAT;WENTRUP, CURT, J. ORG. CHEM., 56,(1991) N, C. 2286-2289
作者:FREIERMUTH, BEAT、WENTRUP, CURT
DOI:——
日期:——
Direct observation of .alpha.-oxo ketenes formed from 1,3-dioxin-4-ones and the enols of .beta.-keto esters
作者:Beat Freiermuth、Curt Wentrup
DOI:10.1021/jo00007a008
日期:1991.3
The enol forms of beta-keto esters thermolyze to alcohols and alpha-oxo ketenes, which are characterized by low-temperature IR spectroscopy and on warming regenerate the beta-hydroxy-alpha,beta-unsaturated esters. The matrix isolated s-Z and s-E forms of alpha-oxo ketenes are characterized and photochemically converted into other conformers or sites. Matrix photolysis of 2,2,6-trimethyl-1,3-dioxin-4-one gives the s-Z acetylketene initially. Alpha-Oxo ketenes polymerize in the cold and dimerize only at elevated temperatures.
Periselectivity in the aza-Diels–Alder Cycloaddition between α-Oxoketenes and <i>N</i>-(5-Pyrazolyl)imines: A Combined Experimental and Theoretical Study
N-(5-pyrazolyl)imines as the 4π partners at their 2-azadiene moiety. In contrast, other cyclic and acyclic α-oxoketenes lead preferentially to 1,3-oxazin-4-ones, which now involves the α-oxoketenes as the 4π partners at their 1-oxadiene moiety and the N-(5-pyrazolyl)imines as the 2π partners at their C═N double bond. A computational modeling study using DFT methods allowed rationalizing this change of periselectivity: