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

• both the N-1 and N-3 nitrogen atoms. At the same time the iPr and Ph moieties served as bulkier substituents for investigations into steric effects. Similar to the N-1 and N-3 nitrogen atoms, 4-t-Bu, 4-Me, 4-F and 4-CF3 groups were incorporated into the aromatic site at position 2 to investigate the

Stereo- and regioselectivity of the hetero-Diels–Alder reaction of nitroso derivatives with conjugated dienes

• Lucie Brulíková,
• Aidan Harrison,
• Marvin J. Miller and
• Jan Hlaváč

Beilstein J. Org. Chem. 2016, 12, 1949–1980, doi:10.3762/bjoc.12.184

• hetero-Diels–Alder reaction. In the reaction of arylnitroso dienophiles containing a nitro group in close proximity to the reaction center, unsubstituted dienes show a higher reactivity than substituted dienes, due to steric effects. Mechanistic studies of the nitroso hetero-Diels–Alder reaction

• -lactams 63 (Scheme 16) [95], which is in accordance with the general prediction. The exclusive regioselectivity of this reaction is due to steric effects. Similar conclusions result from the reaction of 1,3-butadienes 65 with various nitroso heterodienophiles 66, giving proximal isomer 67 (Scheme 17) [85

Experimental and theoretical investigations on the high-electron donor character of pyrido-annelated N-heterocyclic carbenes

• Michael Nonnenmacher,
• Dominik M. Buck and
• Doris Kunz

Beilstein J. Org. Chem. 2016, 12, 1884–1896, doi:10.3762/bjoc.12.178

• electronic properties of the carbene influence the CO stretching modes, but also steric effects and the coupling of stretching modes. The latter two drawbacks have recently been overcome by calculating the metal–ligand electronic parameter (MLEP) [36]. Separating the influence of the σ-donor and π-acceptor

Practical synthetic strategies towards lipophilic 6-iodotetrahydroquinolines and -dihydroquinolines

• David R. Chisholm,
• Garr-Layy Zhou,
• Ehmke Pohl,
• Roy Valentine and
• Andrew Whiting

Beilstein J. Org. Chem. 2016, 12, 1851–1862, doi:10.3762/bjoc.12.174

• reaction was conducted with a variety of quinolin-2-ones bearing differing alkyl substituents in order to ascertain whether steric effects promote collapse of the intermediate aluminium complex via fragmentation/elimination, and to assess the generality of this approach. Table 2 highlights the effect of

Flow carbonylation of sterically hindered ortho-substituted iodoarenes

• Carl J. Mallia,
• Gary C. Walter and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2016, 12, 1503–1511, doi:10.3762/bjoc.12.147

• . Structure D (Figure 2) is a top view of the crystal structure illustrating how the methyl group sits directly over the axial position of the palladium which would introduce steric effects inhibiting the CO coordination on the intermediate aryl complex. As the carbonylation step becomes slower, the competing

The hydrolysis of geminal ethers: a kinetic appraisal of orthoesters and ketals

• Sonia L. Repetto,
• James F. Costello,
• Craig P. Butts,
• Joseph K. W. Lam and
• Norman M. Ratcliffe

Beilstein J. Org. Chem. 2016, 12, 1467–1475, doi:10.3762/bjoc.12.143

• presented (Figure 1). As anticipated, orthoacetates possessing ethoxy substituents are the most rapidly hydrolysed acyclic systems. Both entropic and steric effects are believed to account for the relatively fast rates of hydrolysis of cyclic orthoesters with respect to ketals. Rate increases within five

Synthesis of ferrocenyl-substituted 1,3-dithiolanes via [3 + 2]-cycloadditions of ferrocenyl hetaryl thioketones with thiocarbonyl S-methanides

• Grzegorz Mlostoń,
• Róża Hamera-Fałdyga,
• Anthony Linden and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2016, 12, 1421–1427, doi:10.3762/bjoc.12.136

• results in the preferred concerted [3 + 2]-cycloaddition. It is well known that this mechanism, controlled by frontier-orbital (FMO) interactions, is strongly influenced by steric effects in the case of C=S dipolarophiles [8][17]. Conclusion The presented study indicated that ferrocenyl thioketones show

Reactivity studies of pincer bis-protic N-heterocyclic carbene complexes of platinum and palladium under basic conditions

• David C. Marelius,
• Curtis E. Moore,
• Arnold L. Rheingold and
• Douglas B. Grotjahn

Beilstein J. Org. Chem. 2016, 12, 1334–1339, doi:10.3762/bjoc.12.126

• even longer. In 1968, Wanzlick and Öfele separately synthesized mercury(II) and chromium(0) imidazol-2-ylidene complexes [3]. Nearly 50 years of NHC ligand research have demonstrated the importance of the electronic and steric effects that can be modified by altering the alkyl or aryl groups on each

Is conformation a fundamental descriptor in QSAR? A case for halogenated anesthetics

• Maria C. Guimarães,
• Mariene H. Duarte,
• Josué M. Silla and
• Matheus P. Freitas

Beilstein J. Org. Chem. 2016, 12, 760–768, doi:10.3762/bjoc.12.76

• dictated by hydrophobic interactions of R4 with amino acid residues and by low steric effects surrounding R1. Thus, 2D structural information provided by MIA descriptors (particularly related to the connectivity of different atoms in the present case) was capable of modeling and interpreting biochemical

Synthesis and in vitro cytotoxicity of acetylated 3-fluoro, 4-fluoro and 3,4-difluoro analogs of D-glucosamine and D-galactosamine

• Štěpán Horník,
• Lucie Červenková Šťastná,
• Petra Cuřínová,
• Jan Sýkora,
• Kateřina Káňová,
• Roman Hrstka,
• Ivana Císařová,
• Martin Dračínský and
• Jindřich Karban

Beilstein J. Org. Chem. 2016, 12, 750–759, doi:10.3762/bjoc.12.75

• groups at C-2 or C-4, or by an internal fluorine attack as in SNi substitution. A simple SN2 displacement leading to configurational inversion is probably suppressed by the steric effects of the axially positioned groups at C-2 and C-4, and repulsive effects of their aligned dipoles [51]. Compounds 11

Strecker degradation of amino acids promoted by a camphor-derived sulfonamide

• M. Fernanda N. N. Carvalho,
• M. João Ferreira,
• Ana S. O. Knittel,
• Maria da Conceição Oliveira,
• João Costa Pessoa,
• Rudolf Herrmann and
• Gabriele Wagner

Beilstein J. Org. Chem. 2016, 12, 732–744, doi:10.3762/bjoc.12.73

• Supporting Information File 4. The activation barriers for these reactions are very high (≈50 kcal/mol), a fact which clearly speaks against this path. We think that steric effects in general are responsible for the high barriers since the carboxyl group has to approach the bicyclic system from above or

Interactions of cyclodextrins and their derivatives with toxic organophosphorus compounds

• Sophie Letort,
• Sébastien Balieu,
• William Erb,
• Géraldine Gouhier and
• François Estour

Beilstein J. Org. Chem. 2016, 12, 204–228, doi:10.3762/bjoc.12.23

• binding constant values and the hydrophobicity of the pesticides, suggesting that steric effects are probably predominantly involved in complex formation. The inclusion of the apolar heterocyclic ring into the CD cavity is the most likely situation to occur. γ-CD has the largest secondary alcohols rim

Scope and limitations of the dual-gold-catalysed hydrophenoxylation of alkynes

• Adrián Gómez-Suárez,
• Yoshihiro Oonishi,
• Anthony R. Martin and
• Steven P. Nolan

Beilstein J. Org. Chem. 2016, 12, 172–178, doi:10.3762/bjoc.12.19

• hydroxy functional groups likely reduces this difference. To put these results in context, the previously reported methodology required 10 mol % of AuCl3 and 96 h in order to obtain similar yields for 4aq [26]. Moreover, only 7% of 4ap could be isolated after 168 h [26]. Electronic and steric effects on

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

• complexes may be determined by steric effects of both monomeric moieties. To evaluate only the sterics, topographic steric maps were used, which are calculated through the SambVca package developed by Cavallo et al. [66]. This analysis allows the rationalization of the first coordination sphere around metal

Beyond catalyst deactivation: cross-metathesis involving olefins containing N-heteroaromatics

• Kevin Lafaye,
• Cyril Bosset,
• Lionel Nicolas,
• Amandine Guérinot and
• Janine Cossy

Beilstein J. Org. Chem. 2015, 11, 2223–2241, doi:10.3762/bjoc.11.241

• the nitrogen atom, steric effects cannot be neglected. Another example of RCM involving alkenes that possess 2-chloropyridines was reported to produce dihydroisoquinoline 57 from 2,6-dichloro-3,4-diallylpyridine (56) [60]. The addition of benzoquinone prevented the isomerization of the double bond and

• for avoiding the nitrogen-induced deactivation of the catalyst by both electronic and steric effects (Scheme 22). Macrocycles embedding N-heteroaromatics have been prepared using a RCM reaction. Shirbate et al. used a RCM to synthesize normuscopyridine and analogues [62]. When a diastereomeric mixture

Stereochemistry of ring-opening/cross metathesis reactions of exo- and endo-7-oxabicyclo[2.2.1]hept-5-ene-2-carbonitriles with allyl alcohol and allyl acetate

• Piotr Wałejko,
• Michał Dąbrowski,
• Lech Szczepaniak,
• Jacek W. Morzycki and
• Stanisław Witkowski

Beilstein J. Org. Chem. 2015, 11, 1893–1901, doi:10.3762/bjoc.11.204

• the 2-hydroxy derivative (FG = OH) provided an equimolar ratio of both type A products. The authors have suggested that the observed regioselectivity comes from steric effects that favour formation of 1-3 over 1-2 metallacycles in the former case (see [20]). The completely regioselective ROCM of 2

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

• and the conclusion was that any generalization could be done about the side/bottom stability of the coordination intermediate, as well as it is not possible for the first Grubbs catalysts [9]. Overall, the inclusion of a polar solvent and the absence of strong steric effects, i.e., with less bulky

• representative substrate, and is useful to focus on the study of steric effects of the substrate, reinforced the steric hindrance aspect replacing one or both mesityl groups of NHC ligand by methyl groups. Bearing the asymmetric catalysts 17–19, particularly complex 19 can be compared to 16 but introducing

• , respectively. Steric effects have little influence on the absolute C2H4 binding energy, E of 3rd column in Table 2, since rather similar values are calculated for 2 and 5 (−18.6 and −19.1 kcal/mol, respectively). Differently, electronic effects influence the ability of the Ru atom to capture C2H4, particularly

Consequences of the electronic tuning of latent ruthenium-based olefin metathesis catalysts on their reactivity

• Karolina Żukowska,
• Eva Pump,
• Aleksandra E. Pazio,
• Krzysztof Woźniak,
• Luigi Cavallo and
• Christian Slugovc

Beilstein J. Org. Chem. 2015, 11, 1458–1468, doi:10.3762/bjoc.11.158

• assuming, that the isomerization of trans-5a to cis-5a is a concurring reaction, thus slowing down the polymerization reaction. The reason for the unexpectedly, at first sight, delayed initiation of 14 and 15 can most probably be attributed to steric effects. It is known that a coordination at the free

• occurrence of the cycloisomerization reaction, which are more important at higher temperatures of 140 °C. In ROMP, again the position of the trans–cis equilibrium is the most crucial factor governing the initiation efficacy. Additionally, it has been shown, that steric effects of the substitution are

Antioxidant potential of curcumin-related compounds studied by chemiluminescence kinetics, chain-breaking efficiencies, scavenging activity (ORAC) and DFT calculations

• Adriana K. Slavova-Kazakova,
• Silvia E. Angelova,
• Timur L. Veprintsev,
• Petko Denev,
• Davide Fabbri,
• Maria Antonietta Dettori,
• Maria Kratchanova,
• Vladimir V. Naumov,
• Aleksei V. Trofimov,
• Rostislav F. Vasil’ev,
• Giovanna Delogu and
• Vessela D. Kancheva

Beilstein J. Org. Chem. 2015, 11, 1398–1411, doi:10.3762/bjoc.11.151

• with our data obtained for the couple monomer 2/dimer 6. It might be concluded that it does not matter how the two half-curcumin moieties are combined: as curcumin 1, or as C2-symmetric dimer 6. Dimer 8 showed a 1.3-fold higher kA value in comparison with monomer 4 probably due to the steric effects of

The chemical behavior of terminally tert-butylated polyolefins

• Dagmar Klein,
• Henning Hopf,
• Peter G. Jones,
• Ina Dix and
• Ralf Hänel

Beilstein J. Org. Chem. 2015, 11, 1246–1258, doi:10.3762/bjoc.11.139

• crystallographic symmetry, but displays twofold symmetry to a good approximation (rms deviation 0.015 Å). The torsion angles across the central C1…C4 moiety are C5–C1…C4–C7 53.4° and C6–C1…C4–C8 −14.6°. Distortions from "normal" dimensions may be attributed to the steric effects of the tert-butyl groups; thus the

Tuning the size of a redox-active tetrathiafulvalene-based self-assembled ring

• Sébastien Bivaud,
• Sébastien Goeb,
• Vincent Croué,
• Magali Allain,
• Flavia Pop and
• Marc Sallé

Beilstein J. Org. Chem. 2015, 11, 966–971, doi:10.3762/bjoc.11.108

• much less constrained system is observed in the case of the M6L3 complex, characterizing a prismatic structure which is not driven by steric effects but which is mainly governed by thermodynamic aspects. The M6L3 assembly forms a trigonal prismatic structure presenting a cavity defined by 17.7 Å high

Photovoltaic-driven organic electrosynthesis and efforts toward more sustainable oxidation reactions

• Bichlien H. Nguyen,
• Robert J. Perkins,
• Jake A. Smith and
• Kevin D. Moeller

Beilstein J. Org. Chem. 2015, 11, 280–287, doi:10.3762/bjoc.11.32

• relative oxidation potential of the various groups in solution. The group with the lowest oxidation potential is the group that will be oxidized. Chemical oxidations, however, do not have this limitation. They can be selective for one substrate based on steric effects, chirality, or other factors. For this

Anionic sigmatropic-electrocyclic-Chugaev cascades: accessing 12-aryl-5-(methylthiocarbonylthio)tetracenes and a related anthra[2,3-b]thiophene

• Laurence Burroughs,
• John Ritchie,
• Mkhethwa Ngwenya,
• Dilfaraz Khan,
• William Lewis and
• Simon Woodward

Beilstein J. Org. Chem. 2015, 11, 273–279, doi:10.3762/bjoc.11.31

• be expected to limit the potential yield of 7 to only 50% under simple heating (in the absence of other factors). Houk has demonstrated that both electronic donor or acceptor and steric effects favour placing the larger/most electronically biased substituent ‘outwards’ in disrotatory 6π processes [19

Three-component synthesis of C₂F₅-substituted pyrazoles from C₂F₅CH₂NH₂·HCl, NaNO₂ and electron-deficient alkynes

• Pavel K. Mykhailiuk

Beilstein J. Org. Chem. 2015, 11, 16–24, doi:10.3762/bjoc.11.3

• with C2F5CHN2 to give only 3,5-disubstituted pyrazoles. Formation of 3,4-disubstituted isomers was observed. Disubstituted alkynes behaved differently, because of controversial electronic and steric effects. According to the orbital symmetry rules, the [3 + 2] cycloaddition must lead to pyrazoles with

Morita–Baylis–Hillman reaction of acrylamide with isatin derivatives

• Radhey M. Singh,
• Kishor Chandra Bharadwaj and
• Dharmendra Kumar Tiwari

Beilstein J. Org. Chem. 2014, 10, 2975–2980, doi:10.3762/bjoc.10.315

• only the application of the MBH adducts, but in the development of reaction as well [4][5][6][7][8]. Although a very useful reaction, it does have some limitations such as a slow reaction rate, and is effected by electronic parameters and steric effects. Although the reaction has been well-explored