A computational study of base-catalyzed reactions of cyclic 1,2-diones: cyclobutane-1,2-dione

• Nargis Sultana and
• Walter M. F. Fabian

Beilstein J. Org. Chem. 2013, 9, 594–601, doi:10.3762/bjoc.9.64

• the normal mode corresponding to the imaginary frequency. The final structures of both IRC calculations were then completely optimized. An analogous procedure, usually considering several possible reaction coordinates, was used for an initial guess of all other transition states. Bulk solvent effects

Complete σ* intramolecular aromatic hydroxylation mechanism through O₂ activation by a Schiff base macrocyclic dicopper(I) complex

• Albert Poater and
• Miquel Solà

Beilstein J. Org. Chem. 2013, 9, 585–593, doi:10.3762/bjoc.9.63

• states [65][66][67][68][69][70][71][72][73]. Solvent effects including contributions of non-electrostatic terms have been estimated in single-point calculations on the gas-phase-optimized structures, based on the polarizable continuous solvation model (PCM) with CH3CN as a solvent [74][75], i.e., the

• same solvent used experimentally. The relative Gibbs energies reported in this work include energies computed using the B3LYP/6-311G(d,p)//B3LYP/6-31G(d) method together with solvent effects obtained at the B3LYP/6-31G(d) level, and zero-point energies, thermal corrections, and entropy effects

Some aspects of radical chemistry in the assembly of complex molecular architectures

• Béatrice Quiclet-Sire and
• Samir Z. Zard

Beilstein J. Org. Chem. 2013, 9, 557–576, doi:10.3762/bjoc.9.61

• past three decades [2][3][4][5]. Radicals offer many of the properties desired by synthetic organic chemists, as compared to ionic or organometallic reactions: generally mild and neutral experimental conditions; lower sensitivity to steric hindrance; lower susceptibility to the solvent effects; lesser

Asymmetric desymmetrization of meso-diols by C₂-symmetric chiral 4-pyrrolidinopyridines

• Hartmut Schedel,
• Keizo Kan,
• Yoshihiro Ueda,
• Kenji Mishiro,
• Keisuke Yoshida,
• Takumi Furuta and
• Takeo Kawabata

Beilstein J. Org. Chem. 2012, 8, 1778–1787, doi:10.3762/bjoc.8.203

• substituents appears to have decisive effects on the stereochemical course of the asymmetric desymmetrization. Since catalyst 12b showed relatively high enantioselectivity (83% ee) and mono/diacylation ratio (77:14), we next investigated the solvent effects of the asymmetric desymmetrization of 5 with

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

• . Extensive DFT calculations, including solvent effects and dispersion corrections, as well as ab initio calculations provide a plausible description of the reaction mechanism. Keywords: bifunctional organocatalyst; DFT calculations; guanidine-thiourea; Michael addition; organocatalysis; transition states

• produces the Michael product 15 with 66% yield in only 2 h. We therefore decided to study the solvent effects on the reaction outcome in the nitro-Michael reaction of diethylmalonate with trans-β-nitrostyrene further. The results are shown in Table 1. Whereas Michael reactions performed in dichloromethane

Cation affinity numbers of Lewis bases

• Christoph Lindner,
• Raman Tandon,
• Boris Maryasin,
• Evgeny Larionov and
• Hendrik Zipse

Beilstein J. Org. Chem. 2012, 8, 1406–1442, doi:10.3762/bjoc.8.163

• which a cationic substrate reacts to yield a cationic adduct, the reaction now leads from two neutral reactants to a zwitterionic adduct. Solvation energies for this latter type of species are typically significantly larger than for the neutral reactants, indicating a much larger role of solvent effects

Organocatalytic asymmetric Michael addition of unprotected 3-substituted oxindoles to 1,4-naphthoquinone

• Jin-Sheng Yu,
• Feng Zhou,
• Yun-Lin Liu and
• Jian Zhou

Beilstein J. Org. Chem. 2012, 8, 1360–1365, doi:10.3762/bjoc.8.157

• examined the solvent effects, and found that EtOAc turned out to be the most suitable solvent which afforded product 3a in highest ee (Table 1, entries 8–13). Since the reactivity was unsatisfactory, we further tried the use of some additives to improve the reaction rate. The use of MS 4Å could improve the

Cyclodextrin nanosponge-sensitized enantiodifferentiating photoisomerization of cyclooctene and 1,3-cyclooctadiene

• Wenting Liang,
• Cheng Yang,
• Masaki Nishijima,
• Gaku Fukuhara,
• Tadashi Mori,
• Andrea Mele,
• Franca Castiglione,
• Fabrizio Caldera,
• Francesco Trotta and
• Yoshihisa Inoue

Beilstein J. Org. Chem. 2012, 8, 1305–1311, doi:10.3762/bjoc.8.149

• mechanism, we examined the solvent effects on the chromophore conformation of CDNS by circular dichroism spectroscopy and also on the CDNS-sensitized photoisomerization. Indeed, the ICD intensity was enhanced upon the addition of ethanol to an aqueous solution of CDNS (Figure 2b), which encouraged us to

Photoreactions of cyclic sulfite esters: Evidence for diradical intermediates

• Rick C. White,
• Benny E. Arney Jr. and
• Heiko Ihmels

Beilstein J. Org. Chem. 2012, 8, 1208–1212, doi:10.3762/bjoc.8.134

• studies have revealed information on reactive intermediates, solvent effects, and stereochemical outcomes, while synthetic work has pointed to novel approaches for preparing various molecules. For example, deazetation reactions in solvents of increasing viscosity were employed to determine whether the

Chiral multifunctional thiourea-phosphine catalyzed asymmetric [3 + 2] annulation of Morita–Baylis–Hillman carbonates with maleimides

• Hong-Ping Deng,
• De Wang,
• Yin Wei and
• Min Shi

Beilstein J. Org. Chem. 2012, 8, 1098–1104, doi:10.3762/bjoc.8.121

• functionalized cyclopentene 3a was obtained in 54% yield with 96% ee after 24 h (Table 1, entry 1). The examination of solvent effects revealed that toluene is the best solvent (Table 1, entries 2–4). Increasing the ratio of 1a/2a from 1:1.3 to 2:1 afforded 3a in 74% yield and 96% ee, while continuously

The importance of the rotor in hydrazone-based molecular switches

• Xin Su,
• Timo Lessing and
• Ivan Aprahamian

Beilstein J. Org. Chem. 2012, 8, 872–876, doi:10.3762/bjoc.8.98

• it was attributed to kinetic stability of the Z isomer, in addition to solvent effects [27][28][29]. The titration of PPH-4 with TFA only affects the major isomer (Z), while the minor isomer (E) remains intact even in the presence of 10 equiv of TFA. The changes in the 1H NMR spectrum of PPH-4-Z are

Regioselective chlorination and bromination of unprotected anilines under mild conditions using copper halides in ionic liquids

• Han Wang,
• Kun Wen,
• Nurbiya Nurahmat,
• Yan Shao,
• He Zhang,
• Chao Wei,
• Ya Li,
• Yongjia Shen and
• Zhihua Sun

Beilstein J. Org. Chem. 2012, 8, 744–748, doi:10.3762/bjoc.8.84

• as supplementing oxygen or gaseous HCl. Keywords: halogenation; ionic liquids; oxydation; regioselectivity; solvent effects; Introduction Chlorination and bromination of aromatic rings are classical and widely performed transformations, which are useful in many multistep organic-synthesis

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

• geometries to evaluate the vertical transition energies along with the associated transition characteristics. The TDDFT calculations consistently employed the B3LYP functional and 6-31+G(d,p) basis set [13]. Solvent effects were evaluated by using the linear-response polarized-continuum model for ethanol

Development of the titanium–TADDOLate-catalyzed asymmetric fluorination of β-ketoesters

• Lukas Hintermann,
• Mauro Perseghini and
• Antonio Togni

Beilstein J. Org. Chem. 2011, 7, 1421–1435, doi:10.3762/bjoc.7.166

• . Solvent effects The choice of solvent for the catalytic fluorinations with F–TEDA is limited by the solubility of this reagent. Solvents must dissolve the ionic reagent, but not deactivate the Lewis acidic catalyst. Suspensions of F–TEDA in MeCN gave results inferior to saturated F–TEDA solutions in MeCN

• temperature on the halogenation of 6 with catalyst K2.a Solvent effects on selectivity of fluorination of 6 with NFSI and K2. Effect of the fluorinating agent on the catalytic fluorination of F1 with 10 mol % K1. Effects of the variation of the ligand structure and substrate stereochemistry.a,b Supporting

Alkene selenenylation: A comprehensive analysis of relative reactivities, stereochemistry and asymmetric induction, and their comparisons with sulfenylation

• Vadim A. Soloshonok and
• Donna J. Nelson

Beilstein J. Org. Chem. 2011, 7, 744–758, doi:10.3762/bjoc.7.85

• influences such as reaction temperature [41][69] and the nature of the counter ion X [33][69]. Furthermore, additional factors stabilizing the seleniranium ion intermediate in step 1, including solvent effects [33][64], strengthening the Se–C bonds [34][55][56], or the presence of heteroatoms or aryl groups

Kinetic evaluation of the solvolysis of isobutyl chloro- and chlorothioformate esters

• Malcolm J. D’Souza,
• Matthew J. McAneny,
• Dennis N. Kevill,
• Jin Burm Kyong and
• Song Hee Choi

Beilstein J. Org. Chem. 2011, 7, 543–552, doi:10.3762/bjoc.7.62

• chlorothioformate; solvolysis; Introduction Alkyl chloro- and chlorothioformate esters are frequently used precursors [1][2][3][4] in the synthesis of pharmaceutical intermediates. Hence, it is important to comprehend the correlations between their chemical structure, chemical reactivity, and solvent effects. This

Tribenzotriquinacenes bearing three peripheral or bridgehead urea groups stretched into the 3-D space

• Jörg Tellenbröker and
• Dietmar Kuck

Beilstein J. Org. Chem. 2011, 7, 329–337, doi:10.3762/bjoc.7.43

• were in accord with the product of threefold addition. Interestingly, the 1H NMR spectra of compound 7 showed pronounced solvent effects on the NH proton resonances. The outer protons were found to resonate at δ 8.86 in DMSO-d6 but at δ 6.80 in C2D2Cl4, and the inner protons to resonate at δ 6.57 in

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

• Supporting Information File 1. Discussion Intermolecular effects on molecules are widely recognised as being important in both binding and reactions, with solvent effects being the classic example of the latter. The effects of solvation on reactive intermediates can change the outcome of a reaction

• in this solvent mixture. Solvent effects will nevertheless impact upon the pKa calculated, therefore pKa values derived from compounds in binary solvent systems are represented with a prime symbol (') indicating the pKa values are not measured in pure water. Solvents can affect the properties of

The intriguing modeling of cis–trans selectivity in ruthenium-catalyzed olefin metathesis

• Naeimeh Bahri-Laleh,
• Raffaele Credendino and
• Luigi Cavallo

Beilstein J. Org. Chem. 2011, 7, 40–45, doi:10.3762/bjoc.7.7

• is reasonably favored over TS2-trans also with the M06 functional. It is the inclusion of the vibrational/entropic part that makes the M06 cis- and trans transition states of similar energy, (compare the ΔE≠cis–trans and ΔG≠cis–trans values in the gas-phase in Table 1). Inclusion of solvent effects

The catalytic performance of Ru–NHC alkylidene complexes: PCy₃ versus pyridine as the dissociating ligand

• Stefan Krehl,
• Diana Geißler,
• Sylvia Hauke,
• Oliver Kunz,
• Lucia Staude and
• Bernd Schmidt

Beilstein J. Org. Chem. 2010, 6, 1188–1198, doi:10.3762/bjoc.6.136

• ligand is protonated under these conditions which would result in a higher amount of the catalytically active 14-electron species. This interpretation is corroborated by the kinetic data obtained by Adjiman, Taylor et al. in their original investigation on solvent effects [49]. Next, we were interested

Intramolecular hydroxycarbene C–H-insertion: The curious case of (o-methoxyphenyl)hydroxycarbene

• Dennis Gerbig,
• David Ley,
• Hans Peter Reisenauer and
• Peter R. Schreiner

Beilstein J. Org. Chem. 2010, 6, 1061–1069, doi:10.3762/bjoc.6.121

• singles and doubles as well as perturbative triples and taking into account both valence and core electrons [32][33][34]. Again, cc-pVDZ was used as the basis set (AE-CCSD(T)/cc-pVDZ). For the elucidation of solvent effects, M06-2X/cc-pVDZ-computations with the Polarization Continuum Model [35] (PCM) were

Donor-acceptor substituted phenylethynyltriphenylenes – excited state intramolecular charge transfer, solvatochromic absorption and fluorescence emission

• Ritesh Nandy and
• Sethuraman Sankararaman

Beilstein J. Org. Chem. 2010, 6, 992–1001, doi:10.3762/bjoc.6.112

• these molecules is relatively non-polar and devoid of significant solvent and substituent effects. By contrast, the fluorescence emission bands of 1a–g showed significant substituent and solvent effects. The fluorescence emission spectra of 1a–g in cyclohexane, and DMSO are shown in Figure 2. In

Recognition properties of receptors consisting of imidazole and indole recognition units towards carbohydrates

• Monika Mazik and
• André Hartmann

Beilstein J. Org. Chem. 2010, 6, No. 9, doi:10.3762/bjoc.6.9

• change of the binding model; for a discussion on solvent effects in carbohydrate binding by synthetic receptors, see ref. [56]). The interactions between the β-glucoside 6a and the indole-based receptor 5 in CDCl3 were shown to be strong but less favorable than those with the receptor 4. The best fit of