Flash vacuum pyrolysis of tert-butyl β-ketoesters: sterically protected α-oxoketenes.
作者:Regis Leung-Toung、Curt Wentrup
DOI:10.1016/s0040-4020(01)90376-x
日期:1992.9
1b. Ketene 4d does not react with methanol at room temperature, but afforded ester 1d on refluxing for 8 h. FVP of 1b and 1d at temperatures above 650 °C gave the α-oxoketenes 4b and 4d, respectively, unsubstituted dimethyl malonate (1a) and methyl 4,4-dimethyl-3-oxopentanoate (1c), respectively, due to retro-ene reactions with elimination of isobutene, as well as pyrolysis products derived from 1a
产物的红外分光分析表明二甲酯的那一刹那真空pyrolyses(FVP)叔-butylmalonate(1B)和甲基叔丁基(特戊酰基)乙酸乙酯(1D)在约 550°C分别得到相应的叔丁基(羧甲氧基)乙烯酮(4b)和叔丁基(新戊酰基)乙烯酮(4d),但有甲醇损失,以及未反应的1b和1d(Ar基质,12 K或纯净77 K; 10 -5 mbar)。红外光谱监测表明,约4b与甲醇反应。−50°C给出1b。丁烯4d在室温下不与甲醇反应,但在回流8小时后得到酯1d。在高于650°C的温度下,1b和1d的FVP分别产生α-氧代酮4b和4d,这归因于逆烯,分别为未取代的丙二酸二甲酯(1a)和4,4-二甲基-3-氧戊酸甲酯(1c)。消除异丁烯的反应,以及分别衍生自1a和1c的热解产物。α-未取代的β-酮酸酯1a和1c在约500°C(10 -5mbar)和12 K的氩气基质分离出的产物,得到的烯酮4a和4c为s-