与我们之前报道的锰同双核催化剂2a相比,单核锰前体3与醇钾组合的催化剂体系不仅可以用于酯化叔芳基酰胺,还可以用于酯化叔脂肪族酰胺。在3和钾醇盐的化学计量反应、动力学研究和密度泛函理论(DFT)计算的基础上,我们阐明了一种合理的反应机制,其中原位生成的锰-钾异双核物种协同激活酰胺的羰基部分和醇的OH部分。我们还详细揭示了之前的锰同双核体系2 a的反应机理,我们发现锰钾异双核配合物催化酰胺酯化的活化自由能(Δ G ≠)低于锰同双核体系的活化自由能(Δ G ≠ ) ,与实验结果一致。我们进一步应用我们的催化剂系统对伯胺和仲胺的乙酰基部分进行脱保护。
A borontrifluoride–methanolcomplex demonstrated remarkable deprotection selectivity against commonly used amino-protecting groups in the deacetylation of acetanilides and high sensitivity to the steric hindrance of substrates. The scope and limitations of the reaction were explored.
Water at elevated temperatures (WET): reactant, catalyst, and solvent in the selective hydrolysis of protecting groups
作者:Wilmarie Medina-Ramos、Mike A. Mojica、Elizabeth D. Cope、Ryan J. Hart、Pamela Pollet、Charles A. Eckert、Charles L. Liotta
DOI:10.1039/c3gc42569j
日期:——
WET has been successfully employed in the removal of protectinggroups alleviating the need for added strong acids/bases, subsequent neutralization and waste salt elimination. The protocols for the water-mediated removal of several common protectinggroups such as tert-butyl carbamates (N-Boc) from 125 to 150 °C, acetamide (N-Ac) at 275 °C and acetate esters (O-Ac) at 250 °C are reported for different
“Goldilocks Effect” of Water in Lewis-Brønsted Acid and Base Catalysis
作者:Benedict J. Barron、Wing-Tak Wong、Pauline Chiu、King Kuok Hii
DOI:10.1021/acscatal.6b00800
日期:2016.7.1
nucleophilic amines leads to the poisoning of the (monomeric) Lewis acidic catalyst, and significant competitive formation of side products were observed. In contrast, good yields and enantioselectivities can be attained by employing the Brønsted basic–Lewis acidic dimeric Pd catalyst, in combination with PDA derivatives protonated by triflic acid. In this case, the presence of the right amount of water was
A New Class of Low-Molecular-Weight Amphiphilic Gelators
作者:Nils Mohmeyer、Hans-Werner Schmidt
DOI:10.1002/chem.200400716
日期:2005.1.21
A new powerful class of low-molecular-weightamphiphilic compounds has been synthesized and their structure-property relationships with respect to their gelation ability of organic solvents have been investigated. These compounds are able to gel organic solvents over a broad range of polarity. Especially polar solvents such as valeronitrile and gamma-butyrolactone can be gelled even at concentrations