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

Stereoselective synthesis of perillaldehyde-based chiral β-amino acid derivatives through conjugate addition of lithium amides

• Zsolt Szakonyi,
• Reijo Sillanpää and
• Ferenc Fülöp

Beilstein J. Org. Chem. 2014, 10, 2738–2742, doi:10.3762/bjoc.10.289

• synthesis of β-peptides and 1,3-heterocycles in three steps. The steric effects of the isopropyl group at position 4 and of the α-methyl substituent of (R)-N-benzyl-N-α-methylbenzylamine on the reactivity were also studied and, upon application of a chiral amine, excellent stereoselectivity of the conjugate

Superoxide chemistry revisited: synthesis of tetrachloro-substituted methylenenortricyclenes

• Basavaraj M. Budanur and
• Faiz Ahmed Khan

Beilstein J. Org. Chem. 2014, 10, 2531–2538, doi:10.3762/bjoc.10.264

• solubility of the KO2 [16], we tried to use 18-crown-6 and to change the temperature to effect the rate of the reaction. We did not notice any significant difference in the rate under these conditions. To study the scope and limitations and to probe the electronic and steric effects of this reaction

• . Biphenyl-substituted adducts 3f/4f yielded nortricyclene derivative 5f smoothly at rt. But naphthyl-substituted adducts 3g/4g furnished the title product 5g at 60 °C, probably due to steric effects (Scheme 2). The other substrates having alkyl substituents on the phenyl ring 3h, 3i/4i afforded the

Structure/affinity studies in the bicyclo-DNA series: Synthesis and properties of oligonucleotides containing bc^en-T and iso-tricyclo-T nucleosides

• Branislav Dugovic,
• Michael Wagner and
• Christian J. Leumann

Beilstein J. Org. Chem. 2014, 10, 1840–1847, doi:10.3762/bjoc.10.194

• , destabilization of DNA as complement is lower (ΔTm −2.5 °C) while that of RNA is higher (ΔTm −4.8 °C), this despite the fact that the sugar conformations of the monomers (see Figure 2) are virtually identical. The differential behavior therefore has to be attributed to steric effects of the cyclopropyl methylene

Rational design of cyclopropane-based chiral PHOX ligands for intermolecular asymmetric Heck reaction

• Marina Rubina,
• William M. Sherrill,
• Alexey Yu. Barkov and
• Michael Rubin

Beilstein J. Org. Chem. 2014, 10, 1536–1548, doi:10.3762/bjoc.10.158

• critical enzyme binding sites. Analogously, we anticipated that incorporation of a three-membered cycle in the ligand structure [60][61][62][63] would impart rigidity to the ligand backbone and provide conformationally constrained systems with amplified steric effects, which can be easily modelled and

Carbohydrate PEGylation, an approach to improve pharmacological potency

• M. Eugenia Giorgi,
• Rosalía Agusti and
• Rosa M. de Lederkremer

Beilstein J. Org. Chem. 2014, 10, 1433–1444, doi:10.3762/bjoc.10.147

• products, depending on the number of lysine residues in the molecule. Random PEGylation may have undesired steric effects, shielding active sites in the protein or disrupting its tertiary structure [24]. PEGylation may be also directed to the side-chain amide nitrogen of Asn. In order to improve the

• steric effects [31]. The strategy is based on the finding that certain PEGylated nucleotide-sugars are effectively transferred to a glycan acceptor by the corresponding glycosyltransferase. A modified sialic acid PEGylated at the 5’-amino position in the CMP nucleotide (CMP-SA-5-NHCOCH2NHPEG) can be

Synthesis of ethoxy dibenzooxaphosphorin oxides through palladium-catalyzed C(sp²)–H activation/C–O formation

• Seohyun Shin,
• Dongjin Kang,
• Woo Hyung Jeon and
• Phil Ho Lee

Beilstein J. Org. Chem. 2014, 10, 1220–1227, doi:10.3762/bjoc.10.120

• selectively converted to the cyclized products (2c) in 66% yield due to steric effects. In the case of 4-tert-butyl, the desired product 2e was obtained in 65% yield. Substrate 1f, characterized by an electron-donating 4-methoxy group, was cyclized to dibenzooxaphosphorin oxide 2f in 65% yield under aerobic

• -dimethoxyphenyl group at 2-position turned out to be compatible with the Pd-catalyzed oxidative cyclization. There are no regioisomers formed due to steric effects. Substrate 3c bearing a chloro group was selectively cyclized to afford 4c in 64% yield. To our delight, the present method worked equally well even

Conformational analysis of 2,2-difluoroethylamine hydrochloride: double gauche effect

• Josué M. Silla,
• Claudimar J. Duarte,
• Rodrigo A. Cormanich,
• Roberto Rittner and
• Matheus P. Freitas

Beilstein J. Org. Chem. 2014, 10, 877–882, doi:10.3762/bjoc.10.84

• interactions, such as steric effects and dipolar (electrostatic) interactions. On the other hand, non-Lewis-type interactions refer to electron delocalization from filled to empty orbitals, such as hyperconjugation. Indeed, the σCH→σ*CF hyperconjugative interaction has been found to be the main factor

Aza-Diels–Alder reaction between N-aryl-1-oxo-1H-isoindolium ions and tert-enamides: Steric effects on reaction outcome

• Amitabh Jha,
• Ting-Yi Chou,
• Zainab ALJaroudi,
• Bobby D. Ellis and
• T. Stanley Cameron

Beilstein J. Org. Chem. 2014, 10, 848–857, doi:10.3762/bjoc.10.81

• –Alder reaction [23][24] and dehydration sequence [25][26] (Scheme 1). As mentioned earlier, N-aryl-1-oxo-1H-isoindolium ions (A, Scheme 1) undergo [4 + 2] imino-Diels–Alder cyclization with electron-rich alkenes [11][12][13][14][15][16][17], the steric effects on the outcome of these reactions has not

• the boat”) of the electron-donating substituents on the dienophile (Scheme 2). To further understand the steric effects, we elected to study this transformation on ortho-substituted aniline-derived N-acyliminium cations. Nine N-(2-substituted-aryl)-3-hydroxyisoindolinones (Table 2) were prepared using

Synthesis of chiral N-phosphinyl α-imino esters and their application in asymmetric synthesis of α-amino esters by reduction

• Yiwen Xiong,
• Haibo Mei,
• Lingmin Wu,
• Jianlin Han,
• Yi Pan and
• Guigen Li

Beilstein J. Org. Chem. 2014, 10, 653–659, doi:10.3762/bjoc.10.57

• -substituent led to lower yield due to steric effects (Table 2, entry 7). Besides, the reaction with ethyl ester also worked well and resulted in a slightly lower yield (Table 2, entry 11). Optimization of the asymmetric reduction reaction conditions Then, the obtained chiral N-phosphinyl α-imino esters were

One-pot three-component synthesis and photophysical characteristics of novel triene merocyanines

• Christian Muschelknautz,
• Robin Visse,
• Jan Nordmann and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2014, 10, 599–612, doi:10.3762/bjoc.10.51

• of the merocyanines 8 begins with a 1,4-dipolar cyclization of 13 furnishing the highly substituted cyclobutene intermediate 14. Finally, the conrotatory electrocyclic ring opening of the cyclobutene occurs under thermodynamic control, which is obviously only governed by steric effects as reflected

Isocyanide-based multicomponent reactions towards cyclic constrained peptidomimetics

• Gijs Koopmanschap,
• Eelco Ruijter and
• Romano V.A. Orru

Beilstein J. Org. Chem. 2014, 10, 544–598, doi:10.3762/bjoc.10.50

• -3CR-approach with enantiopure monoterpene-based β-amino acids [43] (19, Scheme 8), giving 22 as major isomer [44]. The stereoselectivity for 22 was explained by the steric effects of the dimethyl bridge that might prefer a Re-attack of the isocyanide. Compared to methanol, again the reaction in water

Concise, stereodivergent and highly stereoselective synthesis of cis- and trans-2-substituted 3-hydroxypiperidines – development of a phosphite-driven cyclodehydration

• Peter H. Huy,
• Julia C. Westphal and
• Ari M. P. Koskinen

Beilstein J. Org. Chem. 2014, 10, 369–383, doi:10.3762/bjoc.10.35

• secondary OH group proceeded (with PPh3 and P(OEt)3) in very high chemoselectivity most likely due to steric effects. The corresponding aziridine of 9a clearly resulting from activation of the secondary hydroxy group and subsequent fast 3-exo-trig cyclisation was only obtained as a sideproduct at higher

Additive-assisted regioselective 1,3-dipolar cycloaddition of azomethine ylides with benzylideneacetone

• Chuqin Peng,
• Jiwei Ren,
• Jun-An Xiao,
• Honggang Zhang,
• Hua Yang and
• Yiming Luo

Beilstein J. Org. Chem. 2014, 10, 352–360, doi:10.3762/bjoc.10.33

• ′-diarylspiro(indoline-3,2′-pyrrolidin)-2-one was formed when using chalcone or dienone as dipolarophiles [20][31]. Presumably, this might be attributed to the electronic and steric effects of the acetyl group. Therefore, reaction conditions including various solvents and additives (Table 1, entries 2–9) were

Oligomeric epoxide–amine adducts based on 2-amino-N-isopropylacetamide and α-amino-ε-caprolactam: Solubility in presence of cyclodextrin and curing properties

• Julian Fischer and
• Helmut Ritter

Beilstein J. Org. Chem. 2013, 9, 2803–2811, doi:10.3762/bjoc.9.315

• randomly methylated β-cyclodextrin (RAMEB-CD) were added (9β). After that, the cloud point shifted significantly up to 36 °C, which is remarkable since PNIPAM does not interact with β-CD [14]. Explanation for this can be steric effects, since the isopropyl group in our system 9 is placed not so close at

Diastereoselectivity in the Staudinger reaction of pentafluorosulfanylaldimines and ketimines

• Alexander Penger,
• Cortney N. von Hahmann,
• Alexander S. Filatov and
• John T. Welch

Beilstein J. Org. Chem. 2013, 9, 2675–2680, doi:10.3762/bjoc.9.303

• number of different ylides [16]. The reactions of α-pentafluorosulfanyl carbonyl compounds are governed by a combination of the substantial dipole moment and unique steric effects of the octahedral SF5 group. Aliphatic SF5-containing derivatives of biologically active compounds are not well-known. One

Recent advances in transition metal-catalyzed Csp²-monofluoro-, difluoro-, perfluoromethylation and trifluoromethylthiolation

• Grégory Landelle,
• Armen Panossian,
• Sergiy Pazenok,
• Jean-Pierre Vors and
• Frédéric R. Leroux

Beilstein J. Org. Chem. 2013, 9, 2476–2536, doi:10.3762/bjoc.9.287

• initiator. The reaction was achieved with α,β-unsaturated carboxylic acids bearing electron-donating groups, as well as with heteroarene substituted acrylic acids, and the desired products were isolated in modest to good yields (Table 30). Steric effects do not appear to have an influence on the outcome of

ML212: A small-molecule probe for investigating fluconazole resistance mechanisms in Candida albicans

• Willmen Youngsaye,
• Cathy L. Hartland,
• Barbara J. Morgan,
• Amal Ting,
• Partha P. Nag,
• Benjamin Vincent,
• Carrie A. Mosher,
• Joshua A. Bittker,
• Sivaraman Dandapani,
• Michelle Palmer,
• Luke Whitesell,
• Susan Lindquist,
• Stuart L. Schreiber and
• Benito Munoz

Beilstein J. Org. Chem. 2013, 9, 1501–1507, doi:10.3762/bjoc.9.171

• different positions about the ring to probe for further electronic and steric effects associated with this region (Table 3). With regards to steric requirements, it appears that neither the para- (compounds 30–34) nor ortho-positions (compounds 39 and 40) are particularly amenable to functionalization

True and masked three-coordinate T-shaped platinum(II) intermediates

• Manuel A. Ortuño,
• Salvador Conejero and
• Agustí Lledós

Beilstein J. Org. Chem. 2013, 9, 1352–1382, doi:10.3762/bjoc.9.153

Incorporation of perfluorohexyl-functionalised thiophenes into oligofluorene-truxenes: synthesis and physical properties

• Neil Thomson,
• Alexander L. Kanibolotsky,
• Joseph Cameron,
• Tell Tuttle,
• Neil J. Findlay and
• Peter J. Skabara

Beilstein J. Org. Chem. 2013, 9, 1243–1251, doi:10.3762/bjoc.9.141

• the p-orbital overlap, breaking the effective conjugation length [15]. This planarity can be perturbed by the steric effects of substituents attached to the hetero- or carbocycles in the conjugated backbone. In order to observe if the position of the perfluorohexyl chains would have an effect, two