发现在沸腾的三氟乙酸(TFA)中发生酰基戊二甲基苯与活化的芳烃(如苯甲醚)之间的容易的转酰基作用。通过产物分离和动力学阐明了乙酰戊五甲基苯(AcPMB)和苯甲醚与TFA的转酰化机理。该反应进行经由AcPMB的可逆protodeacetylation涉及的本位-protonated中间体B,得到五甲基苯和乙三氟乙酸酐,接着通过混合酸酐苯甲醚不可逆乙酰化。从而导致该机构本位-protonated中间体B由acetylmesitylene与[反应推导2H] TFA以及3,5-二氘代乙酰基乙酰间苯三甲与TFA的脱乙酰速率。这种中间体的形成还通过在稳定离子条件下在超酸溶液中对AcPMB的13 C nmr光谱研究独立地证实。
Sterically hindered acylarenes are deacylated to arenes in quantitative yields on heating in boiling 85% trifluoroacetic acid. Hindered arenecarboxylic acids undergo decarboxylation under the same conditions to give arenes in high yields.
Trifluoroacetic acid-catalysed transacylation of arenes by acylpentamethylbenzene
作者:Takashi Keumi、Toshio Morita、Takanobu Shimada、Naomi Teshima、Hidehiko Kitajima、G. K. Surya Prakash
DOI:10.1039/p29860000847
日期:——
by the mixed anhydride. The mechanism resulting in an ipso-protonated intermediate B was deduced from the reaction of acetylmesitylene with [2H]TFA as well as from the rate of deacetylation of 3,5-dideuterioacetylmesitylene with TFA. The formation of such an intermediate was also independently confirmed by 13C n.m.r. spectroscopic studies on AcPMB in superacid solutions under stable ion conditions.
发现在沸腾的三氟乙酸(TFA)中发生酰基戊二甲基苯与活化的芳烃(如苯甲醚)之间的容易的转酰基作用。通过产物分离和动力学阐明了乙酰戊五甲基苯(AcPMB)和苯甲醚与TFA的转酰化机理。该反应进行经由AcPMB的可逆protodeacetylation涉及的本位-protonated中间体B,得到五甲基苯和乙三氟乙酸酐,接着通过混合酸酐苯甲醚不可逆乙酰化。从而导致该机构本位-protonated中间体B由acetylmesitylene与[反应推导2H] TFA以及3,5-二氘代乙酰基乙酰间苯三甲与TFA的脱乙酰速率。这种中间体的形成还通过在稳定离子条件下在超酸溶液中对AcPMB的13 C nmr光谱研究独立地证实。
Regioselective side-chain nitration of polymethylbenzenes directed by an acyl function and its application to the synthesis of polysubstituted phthalic acid derivatives