Widely useful DMAP-catalyzed esterification under auxiliary base- and solvent-free conditions
Widely useful DMAP-catalyzed esterification under auxiliary base- and solvent-free conditions
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DOI：
10.1021/ja075824w
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发表时间：
2007-11-28
影响因子：
15
通讯作者：
Ishihara, Kazuaki
中科院分区：
文献类型：
--
作者：
Sakakura, Akira;Kawajiri, Kirnio;Ishihara, Kazuaki
就原子经济性和E因子而言，羧酸与等摩尔量的醇的催化缩合是最理想的。尽管已经报道了几种高活性脱水催化剂，但仍然强烈需要更有效的替代品，因为叔醇、酚、酸敏感醇、氨基酸和难溶醇的脱水酯化反应从未令人满意地进行。在这里，我们报告了对经典 DMAP 催化醇酰化的新见解：令人惊讶的是，仅 0.05-2 mol% 的 DMAP 就可以在无辅助碱和无溶剂的条件下有效促进醇与酸酐的酰化，以高产率得到相应的酯。此外，我们在不使用任何溶剂的情况下实现了市售聚苯乙烯支撑的DMAP的回收和再利用。这些偶然的发现提供了广泛有用且环境友好的酯化方法，该方法可能比催化脱水缩合方法更实用和可靠，特别是对于难以与羧酸直接缩合的反应性较低的醇。
With regard to atom economy and E-factor, catalytic condensation of carboxylic acids with equimolar amounts of alcohols is the most desirable. Although several highly active dehydration catalysts have been reported, more efficient alternatives are still strongly needed because the dehydrative esterification of tertiary alcohols, phenols, acid-sensitive alcohols, amino acids, and hardly soluble alcohols has never proceeded satisfactorily. Here we report new insights into the classical DMAP-catalyzed acylation of alcohols: surprisingly, only a 0.05-2 mol % of DMAP can efficiently promote acylation of alcohols with acid anhydrides under auxiliary base- and solvent-free conditions to give the corresponding esters in high yields. Furthermore, we achieved the recovery and reuse of Commercially available polystyrene-supported DMAP without using any solvents. These serendipitous findings provide widely useful and environmentally benign esterification methods, which might be more practical and reliable than catalytic dehydrative condensation methods, in particular, for the less reactive alcohols which hardly condense with carboxylic acid directly.