Metal-mediated aminocatalysis provides mild conditions: Enantioselective Michael addition mediated by primary amino catalysts and alkali-metal ions

• Matthias Leven,
• Jörg M. Neudörfl and
• Bernd Goldfuss

Beilstein J. Org. Chem. 2013, 9, 155–165, doi:10.3762/bjoc.9.18

• crystallographic data for compound 5. Acknowledgements We thank Eduard Maibach from the Merholz group for performing ESIMS measurements and evaluation of related data. We thank Lars Packschies and the RRZK for providing well furnished HPC systems for efficient quantum chemical calculations. We are grateful to the

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225

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

• -chemical calculations on the mechanism and the observed stereoselectivity. Results and Discussion Synthesis and application of new guanidine-thiourea catalyst 7 The syntheses of new guanidine-thiourea compound 7 was accomplished by known methods [36][38][40][54][55][56] as summarised in Scheme 1. (S,S)-1,2

• -thiourea organocatalyst has been published up until now [50][51][52][53]. This encouraged us to synthesize and investigate the potential of new guanidine-thiourea 7 as organocatalyst for the nitro-Michael addition reactions. Here we report the first results of our investigations, accompanied by quantum

A quantitative approach to nucleophilic organocatalysis

• Herbert Mayr,
• Sami Lakhdar,
• Biplab Maji and
• Armin R. Ofial

Beilstein J. Org. Chem. 2012, 8, 1458–1478, doi:10.3762/bjoc.8.166

• by quantum chemical calculations: The methyl cation affinities (MCAs) of the three carbenes 41–43 are 100–200 kJ mol–1 higher than those of the other Lewis bases in Figure 23 [96]. As the carbenes 41 and 42 have almost identical nucleophilicities and Lewis basicities, the question arose as to why

• different behavior was analyzed by quantum chemical calculations (Figure 25b). In the same way that the nucleophilicity order of the carbenes (41 ≈ 42 > 43, Figure 23) parallels the order of the Lewis basicities (methyl cation affinities) of the model compounds (49c ≈ 49a > 49b, Figure 25b bottom), the

Conformational analysis, stereoelectronic interactions and NMR properties of 2-fluorobicyclo[2.2.1]heptan-7-ols

• Fátima M. P. de Rezende,
• Marilua A. Moreira,
• Rodrigo A. Cormanich and
• Matheus P. Freitas

Beilstein J. Org. Chem. 2012, 8, 1227–1232, doi:10.3762/bjoc.8.137

• .8.137 Abstract Four diastereoisomers of 2-fluorobicyclo[2.2.1]heptan-7-ols were computationally investigated by using quantum-chemical calculations, and their relative energies were analyzed on the basis of stereoelectronic interactions, particularly the presence or otherwise of the F∙∙∙HO

• bond. Keywords: conformational analysis; 2-fluorobicyclo[2.2.1]heptan-7-ols; hydrogen bond; 1hJF,H(O) coupling constant; quantum-chemical calculations; Introduction Intra- and intermolecular hydrogen bonds (HB) play an important role in determining the molecular arrangements and properties, as well

Control over molecular motion using the cis–trans photoisomerization of the azo group

• Estíbaliz Merino and
• María Ribagorda

Beilstein J. Org. Chem. 2012, 8, 1071–1090, doi:10.3762/bjoc.8.119

• molecular motion similar to a hinge, in which the two aromatic rings are arranged at an angle of 90°. The photoisomerization process involves three isomeric forms: (trans,trans), (trans,cis) and (cis,cis). The heats of formation of the three isomers were determined by ab initio quantum chemical calculations

Toward unidirectional switches: 2-(2-Hydroxyphenyl)pyridine and 2-(2-methoxyphenyl)pyridine derivatives as pH-triggered pivots

• Christina Tepper and
• Gebhard Haberhauer

Beilstein J. Org. Chem. 2012, 8, 977–985, doi:10.3762/bjoc.8.110

• was investigated with the help of UV spectroscopy. Quantum chemical calculations at the B3LYP/6-31G* level of theory were performed to show that in the case of 2-(2-methoxyphenyl)-3-methylpyridine and 2-(2-hydroxyphenyl)-3-methylpyridine the rotation during the switching process proceeds

• unidirectional rotation process caused by protonation, the methyl derivatives of 1–4, i.e., 5–8 (Scheme 2) were investigated by using quantum chemical calculations at the B3LYP/6-31G* level of theory. Due to the methyl group, all conformations with a dihedral angle θN–C–C–C(O) of 180° represent energy maxima

Synthesis, solid-state fluorescence properties, and computational analysis of novel 2-aminobenzo[4,5]thieno[3,2-d]pyrimidine 5,5-dioxides

• Kenichirou Yokota,
• Masayori Hagimori,
• Naoko Mizuyama,
• Yasuhisa Nishimura,
• Hiroshi Fujito,
• Yasuhiro Shigemitsu and
• Yoshinori Tominaga

Beilstein J. Org. Chem. 2012, 8, 266–274, doi:10.3762/bjoc.8.28

• reproduced by a series of ab initio quantum-chemical calculations. Keywords: amino group; fluorescence; HOMO/LUMO; pyrimidine; solid-state; Introduction Solid-state fluorescent compounds are currently attracting considerable interest from both theoretical and practical standpoints [1][2][3][4]. Recently

• pyrimidine derivatives. It is thought that these derivatives show strong fluorescence as a result of the presence of a hetero-π-electron conjugated system [7]. The electronic and emission spectra of these new compounds were analyzed computationally by using a series of ab initio quantum-chemical calculations

• initio quantum-chemical calculations. The theoretical analyses quantitatively reproduced the S0→S1 and S1→S0 transitions. The associated HOMO/LUMO distributions and the transition characters were also elucidated theoretically. Experimental General Identifications of compounds and measurements of

Imidazole as a parent π-conjugated backbone in charge-transfer chromophores

• Jiří Kulhánek and
• Filip Bureš

Beilstein J. Org. Chem. 2012, 8, 25–49, doi:10.3762/bjoc.8.4

• ]). These chromophores were synthesized by Debus–Radziszewski synthesis (Scheme 1), as two series of compounds with different acceptors A (NO2 or CN groups), and were investigated by electrochemistry, UV–vis and IR spectroscopy (CN), and quantum-chemical calculations (Table 5). Considering all the above

• were primarily investigated by electronic-absorption spectra, electrochemistry, X-ray analysis, and quantum-chemical calculations. The resulting data set was further processed by factor analysis to deduce the structure–property relationships. The most important structural factors affecting the (non

• within the studied series. The photoinduced absorption, birefringence, and second-harmonic generation of chromophores 88c–93c (D = NMe2) embedded within polymethylmethacrylate matrices were studied and complimented by quantum-chemical calculations. These doped polymer films showed very efficient and

Construction of cyclic enones via gold-catalyzed oxygen transfer reactions

• Leping Liu,
• Bo Xu and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2011, 7, 606–614, doi:10.3762/bjoc.7.71

• transfer of 2-alkynyl-1,5-diketones. The discovery of a [4 + 2] cycloaddition of a furanium intermediate to a carbonyl group was further verified by quantum chemical calculations. The competing [2 + 2] and [4 + 2] reaction coordinates were computed for the simplified substrate 11a, shown in Scheme 10. In

Syntheses and properties of thienyl-substituted dithienophenazines

• Annemarie Meyer,
• Eva Sigmund,
• Friedhelm Luppertz,
• Gregor Schnakenburg,
• Immanuel Gadaczek,
• Thomas Bredow,
• Stefan-S. Jester and
• Sigurd Höger

Beilstein J. Org. Chem. 2010, 6, 1180–1187, doi:10.3762/bjoc.6.135

• -condensed thiophene analogues. These assignments of the thiophene moieties as donors and the phenazine moieties as acceptors are confirmed by quantum-chemical calculations at the density-functional level. Additionally, one of the compounds forms a self-assembled monolayer on a HOPG surface, as imaged by

• , when compared with the optical spectra of the quater- and sexithiophene [28] (Table 2, 19 and 20), a clear red-shift could be observed for both oligomer series, regardless if they are based on 10 or 11, due to the intramolecular donor-acceptor character of the compounds. Quantum chemical calculations

EPR and pulsed ENDOR study of intermediates from reactions of aromatic azides with group 13 metal trichlorides

• Giorgio Bencivenni,
• Riccardo Cesari,
• Daniele Nanni,
• Hassane El Mkami and
• John C. Walton

Beilstein J. Org. Chem. 2010, 6, 713–725, doi:10.3762/bjoc.6.84

• explain the absence of the 19F high-frequency line in our spectrum. DFT computations of radical cation properties Quantum chemical calculations were carried out with the Gaussian 03 programme package [35][36]. Density functional theory with the UB3LYP functional was employed. The equilibrium geometries