Recent advances in the asymmetric phosphoric acid-catalyzed synthesis of axially chiral compounds

• Alemayehu Gashaw Woldegiorgis and
• Xufeng Lin

Beilstein J. Org. Chem. 2021, 17, 2729–2764, doi:10.3762/bjoc.17.185

• functional calculations showed that the chiral phosphoric acid proton forms an H-bond with nitrogen atoms of 1 and the phosphate acts as a chiral counterion, resulting in a [3,3]-sigmatropic rearrangement with controlled stereoselectivity [14][41]. In 2017, Tan and co-workers developed an organocatalytic

• ′-binaphthalenes (BINAMs) from achiral N,N′-binaphthylhydrazines (Scheme 1). In the presence of chiral phosphoric acids (CPA 1), the reaction undergoes a simple [3,3]-sigmatropic rearrangement, giving the corresponding products 2 in good yield (up to 88%) and enantioselectivity (up to 93:7 er). The density

1,2,3,4-Tetrahydro-1,4,5,8-tetraazaanthracene revisited: properties and structural evidence of aromaticity loss

• Arnault Heynderickx,
• Sébastien Nénon,
• Olivier Siri,
• Vladimir Lokshin and
• Vladimir Khodorkovsky

Beilstein J. Org. Chem. 2019, 15, 2059–2068, doi:10.3762/bjoc.15.203

• level optimized and experimental geometry of THTAA and its derivatives show considerable loss of aromaticity within the quinoxaline moiety. Keywords: aromaticity; density functional calculations; heterocycles; hydrogen bonds; X-ray structures; Introduction Quinoxaline derivatives 1 – also called

Experimental and theoretical investigations into the stability of cyclic aminals

• Edgar Sawatzky,
• Antonios Drakopoulos,
• Martin Rölz,
• Christoph Sotriffer,
• Bernd Engels and
• Michael Decker

Beilstein J. Org. Chem. 2016, 12, 2280–2292, doi:10.3762/bjoc.12.221

• exposed to buffered aqueous media with defined pH values. A general trend was observed for all compounds with an accelerated hydrolysis rate as a function of decreasing pH value. Additional density functional calculations revealed that protonation of the N-3 nitrogen can induce hydrolysis into the

Versatile deprotonated NHC: C,N-bridged dinuclear iridium and rhodium complexes

• Albert Poater

Beilstein J. Org. Chem. 2016, 12, 117–124, doi:10.3762/bjoc.12.13

• thermodynamics show a constant and sharp decay of energy, not due to steric factors, but mainly electronics. Computational Details The density functional calculations were performed on all the systems with the Gaussian 09 set of programs [73], Revision D.01, at the BP86 GGA level [74][75][76], adding the Grimme

A comprehensive study of olefin metathesis catalyzed by Ru-based catalysts

• Albert Poater and
• Luigi Cavallo

Beilstein J. Org. Chem. 2015, 11, 1767–1780, doi:10.3762/bjoc.11.192

• asymmetry [17][53]. Then complexes 1 and 14 are representative of the first generation Grubbs catalysts. Finally, several systems are displayed to get insight into the typical properties of free halogen catalysts [54][55]. Computational details The density functional calculations were performed on all the

Substitution effect and effect of axle’s flexibility at (pseudo-)rotaxanes

• Friedrich Malberg,
• Jan Gerit Brandenburg,
• Werner Reckien,
• Oldamur Hollóczki,
• Stefan Grimme and
• Barbara Kirchner

Beilstein J. Org. Chem. 2014, 10, 1299–1307, doi:10.3762/bjoc.10.131

• computational energy profile [22]. The formation of α-cyclodextrin-based [3]pseudorotaxanes in the gas phase was studied by means of density functional calculations [23]. Molecular mechanics calculations were used for a free energy calculation of an α-cyclodextrin rotaxane system and for the investigation of

Site-selective covalent functionalization at interior carbon atoms and on the rim of circumtrindene, a C₃₆H₁₂ open geodesic polyarene

• Hee Yeon Cho,
• Ronald B. M. Ansems and
• Lawrence T. Scott

Beilstein J. Org. Chem. 2014, 10, 956–968, doi:10.3762/bjoc.10.94

• consequence of π-system curvature, the electron densities for the two different faces of circumtrindene are expected to be unequal [57]. Density functional calculations (B3LPY/6-31G*) reveal that the outer surface of circumtrindene should be relatively electron deficient, resembling that of C60, whereas the

Chromatographically separable rotamers of an unhindered amide

• Mario Geffe,
• Lars Andernach,
• Oliver Trapp and
• Till Opatz

Beilstein J. Org. Chem. 2014, 10, 701–706, doi:10.3762/bjoc.10.63

• the rotamers which can readily be separated by HPLC as well as TLC. The experimental results of the different methods were compared to each other as well as to results obtained by DFT calculations. Keywords: amides; density functional calculations; dynamic HPLC; rotamers; thermodynamics

Host–guest complexes of mixed glycol-bipyridine cryptands: prediction of ion selectivity by quantum chemical calculations, part V

• Svetlana Begel,
• Ralph Puchta and
• Rudi van Eldik

Beilstein J. Org. Chem. 2013, 9, 1252–1268, doi:10.3762/bjoc.9.142

• functional calculations, i.e., with pseudo-potentials on the heavy elements and the valence basis set augmented with polarization functions [75][76][77][78][79][80][81][82][83][84][85][86]. During the optimization of the structures no other constraints than symmetry were applied. In addition, the resulting

• chains δ stereochemistry, corresponding to negative and positive algebraic signs. Conversely, the steric configuration of the coordinating bipyridine moiety alternates depending on the size of the complexed metal ion. Experimental Quantum chemical methods We performed B3LYP/LANL2DZp hybrid density

Tandem dinucleophilic cyclization of cyclohexane-1,3-diones with pyridinium salts

• Mostafa Kiamehr,
• Firouz Matloubi Moghaddam,
• Satenik Mkrtchyan,
• Volodymyr Semeniuchenko,
• Linda Supe,
• Alexander Villinger,
• Peter Langer and
• Viktor O. Iaroshenko

Beilstein J. Org. Chem. 2013, 9, 1119–1126, doi:10.3762/bjoc.9.124

• screening of bases and additives revealed that the presence of potassium cations is essential for formation of the product. Keywords: cyclization; density functional calculations; heterocycles; nucleophilic addition; pyridinium salt; Introduction The nucleophilic addition to pyridinium salts has recently

Influence of intramolecular hydrogen bonds on the binding potential of methylated β-cyclodextrin derivatives

• Gerhard Wenz

Beilstein J. Org. Chem. 2012, 8, 1890–1895, doi:10.3762/bjoc.8.218

• was calculated by using density functional theory (basis set B3LYP) [41]. In addition, recent density-functional calculations also took into account strong intermolecular hydrogen bonds of these hydroxy groups with water molecules in aqueous solution [42]. The conformational stabilization of β-CD by

Synthesis and evaluation of new guanidine-thiourea organocatalyst for the nitro-Michael reaction: Theoretical studies on mechanism and enantioselectivity

• Tatyana E. Shubina,
• Matthias Freund,
• Sebastian Schenker,
• Timothy Clark and
• Svetlana B. Tsogoeva

Beilstein J. Org. Chem. 2012, 8, 1485–1498, doi:10.3762/bjoc.8.168

• systems, we decided to carry out a computational investigation of this guanidine-thiourea catalysed nitro-Michael reaction employing density functional calculations. Theoretical studies: DFT calculations The main goal of our calculations was to gain insight into the mechanism of the nitro-Michael addition

Anion–π interactions influence pK_a values

• Christopher J. Cadman and
• Anna K. Croft

Beilstein J. Org. Chem. 2011, 7, 320–328, doi:10.3762/bjoc.7.42

• as phosphate hydrolysis [27][28]. In order to analyse any effects of the aromatic system on the pKa value of the naphthols 1–5 in a complementary fashion, density functional calculations using the M06-2X functional [29], and atoms in molecules (AIM) [30], analyses have been used. Results Preparation

• (−0.27), as might be expected for a through-space effect, and may also be indicative of solvation reducing the apparent localised charge. For a better interpretation of the factors contributing to the changes in measured pKa' values, M06-2X density functional calculations of both the starting materials 1

• -naphthol derivatives 1–5. These derivatives exhibit changes in their pKa' values consistent with the changing electronic nature of R substituent, suggesting an anion–π effect in modulating the hydrogen abstraction process. Density functional calculations indicate that the change in reactivity is likely to