Studies on organic reactions in which supercritical alcohols participate as reaction partners

点击翻译按钮获取中文摘要

In this study, we found some novel reactions, in which supercritical alcohols participate as the reaction partners.1. Alkenes and alkynes with conjugated aromatic rings reacted with supercritical alcohols to afford hydroxyalkylated derivatives and hydrogenated derivatives. Reaction rates of the hydroxyalkylation of alkenes decreased as follows: Ph_2CH = CH_2 > trans-PhCH = CEPh, PhCH = CH_2 > PhCH_2CH = CH_2, and (CH_3)_2CHOH > CH_3CH_2OH > CH_3OH. It can be posturated that the cleavage of the α-C-H bonds in supercritical alcohols is the rate determining step in the hydroxyalkylation of alkenes.2. Carboxylic acids reacted with supercritical primary alcohols to afford esters. The esterification yields 41 were less than 10 % in the reactions using 2-propanol. Benzoic and 2,4,6-trimethylbenzoic acids were esterified using supercritical ^<18>O-methanol. Based on the results of GC/MS of the resulting esters, the reaction mechanism was suggested to be susceptible to steric hindrance of the carboxylic acids. In the cases of carboxylic acids with no steric hindrance around the carboxylic groups, the esters will be formed via the carbonyl-oxygen bond cleavage in the carboxylic group. On the other hand, the esterification of carboxylic acids with steric hindrance will proceed via the carbon-oxygen bond cleavage in the supercritical alcohol.3. Pyrrole was converted to pyrrole-2-carboxylate in supercritical carbon dioxide using cells of Bacillus megaterium PYR 2910, and the yield of the carboxylation reaction in supercritical carbon dioxide was 12 times than under atmospheric pressure.