4030-18-6Relevant articles and documents
Amide rotation trajectories probed by symmetry
Kubyshkin, Vladimir,Budisa, Nediljko
, p. 6764 - 6772 (2017)
Amide rotation of peptidyl-prolyl fragments is an important factor in backbone structure organization of proteins. Computational studies have indicated that this rotation preferentially proceeds through a defined transition-state structure (syn/exo). Here, we complement the computational findings by determining the amide bond rotation barriers for derivatives of the two symmetric proline analogues, meso and racemic pyrrolidine-2,5-dicarboxylic acids. The rotations around these residues represent syn/exo-syn/exo and anti/endo-syn/exo hybrid transition states for the meso and racemic diastereomer, respectively. The rotation barriers are lower for the former rotation by about 9 kJ mol-1 (aqueous medium), suggesting a strong preference for the syn/exo (clockwise) rotation over the anti/endo (anticlockwise) rotation. The results show that both hybrid rotation processes are enthalpically driven but respond differently to solvent polarity changes due to the different transition state dipole-dipole interactions.
Environmentally benign decarboxylative: N-, O-, and S-Acetylations and acylations
Ghosh, Santanu,Purkait, Anisha,Jana, Chandan K.
supporting information, p. 8721 - 8727 (2020/12/30)
An operationally simple and general method for acetylation and acylation of a wide variety of substrates (amines, alcohols, phenols, thiols, and hydrazones) has been reported. Meldrum's acid and its derivatives have been used as an air-stable, non-volatile, cost-effective, and easy to handle acetylating/acylating agent. Easily separable byproducts (CO2 and acetone) allowed the isolation of analytically pure acetylated products without the requirement of work-up and any chromatography. This journal is
IrIII-Catalyzed direct syntheses of amides and esters using nitriles as acid equivalents: A photochemical pathway
Talukdar, Ranadeep
supporting information, p. 5303 - 5308 (2020/04/17)
An unprecedented IrIII[df(CF3)ppy]2(dtbbpy)PF6-catalyzed simple photochemical process for direct addition of amines and alcohols to the relatively less reactive nitrile triple bond is described herein. Various amides and esters are synthesized as the reaction products, with nitriles being the acid equivalents. A mini-library of different types of amides and esters is made using this mild and efficient process, which uses only 1 mol% of photocatalyst under visible light irradiation (λ = 445 nm). The reaction strategy is also efficient for gram-scale synthesis.
Synthesis of Benzofurans and Benzoxazoles through a [3,3]-Sigmatropic Rearrangement: O-NHAc as a Multitasking Functional Group
Yan, Dingyuan,Jiang, Heming,Sun, Wenxue,Wei, Wei,Zhao, Jing,Zhang, Xinhao,Wu, Yun-Dong
supporting information, p. 1646 - 1653 (2019/09/04)
The synthesis of heterocycles relies heavily on diverse sigmatropic rearrangements triggered by the cleavage of X-Y (X, Y = C, O, N, S, I) bonds. However, a unified rearrangement approach for constructing heterocyclic libraries is highly desirable. Encouraged by computational analysis of [3,3]-sigmatropic rearrangements, we can now rapidly synthesize oxa-heterocycles by treating N-phenoxyacetamides (Ph-ONHAc) with compounds containing an sp-hybridized carbon. The generality of the process is illustrated by the late-stage diversification of natural products, including estrone and an approved drug. A combination of experimental and computational studies revealed that the reactions proceed through a facile Claisen-like [3,3]-sigmatropic rearrangement/annulation process.