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

在本研究中，我们发现了一些以超临界醇为反应伙伴的新型反应.含共轭芳环的烯烃和炔烃与超临界醇反应，得到羟烷基化衍生物和氢化衍生物。烯烃羟烷基化反应速率依次为Ph_2CH = CH_2 > trans-PhCH = CEPh，PhCH = CH_2 > PhCH_2CH = CH_2，（CH_3）_2CHOH > CH_3CH_2OH > CH_3OH。超临界醇中α-C-H键的断裂是烯烃羟烷基化反应的速率控制步骤.羧酸与超临界伯醇反应生成酯。在使用2-丙醇的反应中，酯化产率41小于10%。苯甲酸和2，4，6-三甲基苯甲酸用超临界甲醇酯化<18>。基于所得酯的GC/MS结果，反应机理被认为是对羧酸的空间位阻敏感。在羧酸在羧基周围没有空间位阻的情况下，酯将通过羧基中的羰基-氧键断裂形成。另一方面，具有空间位阻的羧酸的酯化反应将通过超临界醇中碳氧键的断裂进行.利用巨大芽孢杆菌PYR 2910细胞在超临界CO2中将吡咯转化为吡咯-2-羧酸酯，超临界CO2中的羧基化反应产率是常压下的12倍。

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.