Structural Analyses of N-Acetylated 4-(Dimethylamino)pyridine (DMAP) Salts
Structural Analyses of N-Acetylated 4-(Dimethylamino)pyridine (DMAP) Salts
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DOI：
10.1002/chem.200901379
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发表时间：
2009-01-01
影响因子：
4.3
通讯作者：
Schreiner, Peter R.
中科院分区：
文献类型：
--
作者：
Lutz, Volker;Glatthaar, Joerg;Schreiner, Peter R.
我们研究了几种 N-乙酰基-4-(二甲基氨基)吡啶 (DMAP) 盐（带有 Cl-、CH3COO- 和 CF3COO- 抗衡离子）的形成，这些盐被认为是 DMAP 催化的醇乙酰化反应中的催化活性物质。利用结合晶体结构分析、变温矩阵红外和核磁共振光谱以及UAHF-PCM-B3LYP/6-311+G(d,p)//B3LYP/6-31G(d)水平的计算技术来检查盐形成的结构和动力学。我们发现了形成紧密离子对的明确证据，这些离子对通过动态氢键相互作用而稳定。在非极性溶剂中，N-乙酰基-DMAP 盐中乙酸酯的亲核性仅允许室温下的稳态浓度小于 1%。因此，我们提出与醇的额外氢键相互作用是后续乙酰化中的关键稳定因素。
We have studied the formation of several N-acetyl-4-(dimethyl-amino)pyridine (DMAP) salts (with Cl-, CH3COO-, and CF3COO- counterions), which are considered to be the catalytically active species in DMAP-catalyzed acetylation reactions of alcohols. Combined crystal structure analyses, variable temperature matrix IR and NMR spectroscopy as well as computational techniques at the UAHF-PCM-B3LYP/6-311+G(d,p)//B3LYP/6-31G(d) level were utilized to examine the structures and dynamics of salt formation. We found clear evidence for the formation of tight ion pairs that are stabilized by dynamic hydrogen-bonding interactions. In nonpoiar solvents, the nucleophilicity of acetate in its N-acetyl-DMAP salt only allows a steady-state concentration smaller 1% at room temperature. Thus, we propose additional hydrogen-bonding interactions with alcohols to be the key stabilization factor in subsequent acetylations.