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

• to avoid the unfavorable steric interaction between the pseudo-axial syn-tert-butyl group and the methylene group of the cyclopropane (Scheme 7). Accordingly, a synergistic steric effect of both the axial P–t-Bu group and a bulky substituent at C4 in dihydrooxazolyl moiety observed in the alternative

Palladium-catalysed cross-coupling reaction of ultra-stabilised 2-aryl-1,3-dihydro-1H-benzo[d]1,3,2-diazaborole compounds with aryl bromides: A direct protocol for the preparation of unsymmetrical biaryls

• Siphamandla Sithebe and
• Ross S. Robinson

Beilstein J. Org. Chem. 2014, 10, 1107–1113, doi:10.3762/bjoc.10.109

• lower yields when compared to other boronate derivatives (Table 2, entries 5 and 6). This was attributed to incomplete conversion of the starting materials possibly due to a steric effect around the boron atom which is consistent with the literature [6][18][19]. The cross-coupling of an electron-rich

Continuous-flow Heck synthesis of 4-methoxybiphenyl and methyl 4-methoxycinnamate in supercritical carbon dioxide expanded solvent solutions

• Phei Li Lau,
• Ray W. K. Allen and
• Peter Styring

Beilstein J. Org. Chem. 2013, 9, 2886–2897, doi:10.3762/bjoc.9.325

• system using styrene, a mixture of the trans-linear (1t) and terminal-branched (1b) isomers were observed with the composition dependent on the system temperature. This may be explained due to a steric effect [34]. In the case of methyl acrylate, proper alignment of the double bond for migratory

Structure of 1,5-benzodiazepinones in the solid state and in solution: Effect of the fluorination in the six-membered ring

• Marta Pérez-Torralba,
• Rosa M. Claramunt,
• M. Ángeles García,
• Concepción López,
• M. Carmen Torralba,
• M. Rosario Torres,
• Ibon Alkorta and
• José Elguero

Beilstein J. Org. Chem. 2013, 9, 2156–2167, doi:10.3762/bjoc.9.253

• ) > b (18 kJ mol−1 in average), the other tautomers having considerably higher energies. Always tautomer b is destabilized by N-methylation (in average, 8.4 kJ mol−1) probably due to a steric effect; the conjugated tautomer b tends to be planar and this is indeed the case for 1H-derivatives 1b, 3b and

Structures of the reaction products of the AZADO radical with TCNQF₄ or thiourea

• Hideto Suzuki,
• Yuta Kawahara,
• Hiroki Akutsu,
• Jun-ichi Yamada and
• Shin’ichi Nakatsuji

Beilstein J. Org. Chem. 2013, 9, 1487–1491, doi:10.3762/bjoc.9.169

• marked difference in reactivity compared with that of TEMPO radical (1), due at least in part to the difference of the steric effect of the extra methyl substituents of the latter radical. Structural formula of TEMPO (1), AZADO (2), TCNQF4 (3) and thiourea (4). Molecular structure of the adduct 5

Anionic cascade reactions. One-pot assembly of (Z)-chloro-exo-methylenetetrahydrofurans from β-hydroxyketones

• István E. Markó and
• Florian T. Schevenels

Beilstein J. Org. Chem. 2013, 9, 1319–1325, doi:10.3762/bjoc.9.148

• established by single-crystal X-ray diffraction analysis (Figure 2). Once again, increasing the steric effect around the tertiary alcohol function of the (Z)-chloro-exo-methylenetetrahydrofurans has a profound influence on the fate of the condensation reaction. A plausible mechanistic rationale is provided in

Catalytic asymmetric tandem Friedel–Crafts alkylation/Michael addition reaction for the synthesis of highly functionalized chromans

• Jiahuan Peng and
• Da-Ming Du

Beilstein J. Org. Chem. 2013, 9, 1210–1216, doi:10.3762/bjoc.9.137

• to 96 h. A similar result was observed in the case of product 3j (Table 4, entry 10). A steric effect was also observed in this reaction. When the substrate 1g bearing two sterically hindered bromine atoms on the phenyl ring was used, the yield and stereoselectivity of the desired product 3k

Facile synthesis of functionalized spiro[indoline-3,2'-oxiran]-2-ones by Darzens reaction

• Qin Fu and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2013, 9, 918–924, doi:10.3762/bjoc.9.105

• ratios. It is known that the closure of the epoxy ring would form cis/trans isomers in the Darzens reaction process. Here the N-benzyl and the N-butyl group in the oxindole moiety may decrease the steric effect of formation of the epoxy ring and lead to the easier formation of the relatively unstable cis

Ring-opening reaction of 2,5-dioctyldithieno[2,3-b:3',2'-d]thiophene in the presence of aryllithium reagents

• Hao Zhong,
• Jianwu Shi,
• Jianxun Kang,
• Shaomin Wang,
• Xinming Liu and
• Hua Wang

Beilstein J. Org. Chem. 2013, 9, 767–774, doi:10.3762/bjoc.9.87

• the aryllithium reagents can intensify the efficiency of the ring-opening process, and the steric effect is another factor that could influence the yield. This ring opening can be applied extensively to derivatives including 2'-arylthio-3,3'-dithiophenyl-2-aldehydes, which may provide access to a

A facile, rapid, one-pot regio/stereoselective synthesis of 2-iminothiazolidin-4-ones under solvent/scavenger-free conditions

• Murugan Sathishkumar,
• Sangaraiah Nagarajan,
• Poovan Shanmugavelan,
• Murugan Dinesh and
• Alagusundaram Ponnuswamy

Beilstein J. Org. Chem. 2013, 9, 689–697, doi:10.3762/bjoc.9.78

• . Apparently, the reason for this can be attributed to the retardation of the nucleophilic attack of the amines on the isothiocyanate due to the steric effect (Figure 2) in the former, and decrease of the nucleophilicity of the amines by the electron-withdrawing group in the latter, thus not affording the

• of the nucleophilic attack of amines on the isothiocyanate due to the steric effect. Possible regio/stereoisomeric products. Stereoselectivity of the reaction directed by A1,3 strain. Plausible mechanism. Regioselective cyclization in 2-iminothiazolidin-4-one synthesis directed by allylic strains

Synthesis and testing of the first azobenzene mannobioside as photoswitchable ligand for the bacterial lectin FimH

• Vijayanand Chandrasekaran,
• Katharina Kolbe,
• Femke Beiroth and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2013, 9, 223–233, doi:10.3762/bjoc.9.26

• of the mannobioside is important both to mediate hydrophilicity and to intensify the steric effect that photoswitching has on the exposition of the terminal mannoside. Conclusion The azobenzene mannosides presented herein resemble a structure quite similar to biaryl mannosides, which have been

N-Heterocyclic carbene–palladium(II)-1-methylimidazole complex catalyzed Mizoroki–Heck reaction of aryl chlorides with styrenes

• Ting-Ting Gao,
• Ai-Ping Jin and
• Li-Xiong Shao

Beilstein J. Org. Chem. 2012, 8, 1916–1919, doi:10.3762/bjoc.8.222

• the reactions, and all reactions took place smoothly to give products 4 in good yields (Table 2, entries 8–12). The reaction between chlorobenzene (2a) and 2,4-dimethylstyrene (3g) only gave product 4l in 67% yield, which may also be due to the steric effect. In addition, acceptable yields can be

Organocatalytic tandem Michael addition reactions: A powerful access to the enantioselective synthesis of functionalized chromenes, thiochromenes and 1,2-dihydroquinolines

• Chittaranjan Bhanja,
• Satyaban Jena,
• Sabita Nayak and
• Seetaram Mohapatra

Beilstein J. Org. Chem. 2012, 8, 1668–1694, doi:10.3762/bjoc.8.191

• efficient steric effect in the transformation. Although the reaction tolerated a broad scope of substrates, the yields as well as enantioselectivities were greatly affected by the electronic and steric effect of the substrates. Compound 1 bearing electron-donating groups afforded the desired product with

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

• steric effect, but it suppresses adventitious metabolism, influences the pKa of functional groups, and alters solution conformation [12]. In this context, conformational screening and theoretical evaluation of 2-fluorobicyclo[2.2.1]heptan-7-ols (2-fluoronorbornan-7-ols, compounds 5–8 in Figure 1

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

• for MBH carbonate 2g, having a chlorine substituent at the ortho-position of the aromatic ring, this produced 3l in lower yield and ee value, perhaps due to the steric effect; reaction of MBH carbonate 2n derived from isobutyraldehyde did not occur (entries 12 and 19). When we utilized dimethyl

• , which attacked the maleimide to produce intermediate II (Scheme 2). Since there is a steric effect between the phenyl group and the benzyl group in intermediate II-B, allylic phosphorus ylide I using its Si-face to attack maleimide is favored (intermediate II-A). Undergoing Michael addition and

Discovery of practical production processes for arylsulfur pentafluorides and their higher homologues, bis- and tris(sulfur pentafluorides): Beginning of a new era of “super-trifluoromethyl” arene chemistry and its industry

• Teruo Umemoto,
• Lloyd M. Garrick and
• Norimichi Saito

Beilstein J. Org. Chem. 2012, 8, 461–471, doi:10.3762/bjoc.8.53

• 2,6-difluorophenylsulfur chlorotetrafluoride were formed in high yields due to the small steric effect of fluorine atom(s). However, bis(2-bromophenyl) disulfide gave a 11:1 mixture of 2-bromophenylsulfur trifluoride and chlorotetrafluoride. 2-Bromophenylsulfur chlorotetrafluoride was a minor product

Intramolecular hydroamination of alkynic sulfonamides catalyzed by a gold–triethynylphosphine complex: Construction of azepine frameworks by 7-exo-dig cyclization

• Hideto Ito,
• Tomoya Harada,
• Hirohisa Ohmiya and
• Masaya Sawamura

Beilstein J. Org. Chem. 2011, 7, 951–959, doi:10.3762/bjoc.7.106

• , it is concluded that the acceleration effect by L1 is not due to an electronic effect rather a steric effect. The time–conversion profiles shown in Figure 3 clearly indicate that the high catalytic efficiency with L1 is due to the improvement of the reaction kinetics and not the thermal stability of

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

• degree of substitution, but rather by a different type of steric effect. Steric effects of alkyl substituents The scatter plots for the reaction of alkenes with PhSeCl enable us to conduct a separate evaluation of three different sources of steric effects and to examine their relative influence on the

• same carbon (geminal) or adjacent carbons (vicinal). Isobutylene reacts faster than cis- or trans-2-butene, but this is in the same order as their IEs and HOMOs, so it appears to be an electronic influence, rather than a steric effect. When the alkene has larger alkyl substituents, the general order of

• magnitude greater (Table 1, entries 20 versus 21, or 26 versus 27). 3. Alkyl branching α to C=C: The data obtained in this study pointed to a new steric effect in linear free energy relationships, which can be defined as alkyl group α-branching. Thus, within each line fit, there is a clear trend dependent

SbCl₃-catalyzed one-pot synthesis of 4,4′-diaminotriarylmethanes under solvent-free conditions: Synthesis, characterization, and DFT studies

• Ghasem Rezanejade Bardajee

Beilstein J. Org. Chem. 2011, 7, 135–144, doi:10.3762/bjoc.7.19

• its resonance effect due to its steric effect. The resonance effect of a meta-nitro group is relatively low and leads to a slightly lower yield of product in comparison to ortho-nitrobenzaldehyde. Thus, in these two cases, the yields are lower than with the para-nitro substituted benzaldehyde. On the

Olefin metathesis in nano-sized systems

• Didier Astruc,
• Abdou K. Diallo,
• Sylvain Gatard,
• Liyuan Liang,
• Cátia Ornelas,
• Victor Martinez,
• Denise Méry and
• Jaime Ruiz

Beilstein J. Org. Chem. 2011, 7, 94–103, doi:10.3762/bjoc.7.13

• one, and it is probably related to the more difficult access to the metal center due to the increasing steric effect at the dendrimer periphery when the generation increases. Analogous ruthenium benzylidene dendrimers were very recently synthesized with two tert-butyl groups on each phosphorus atom

Cross-metathesis of allylcarboranes with O-allylcyclodextrins

• Ivan Šnajdr,
• Zbyněk Janoušek,
• Jindřich Jindřich and
• Martin Kotora

Beilstein J. Org. Chem. 2010, 6, 1099–1105, doi:10.3762/bjoc.6.126

• intermediate and secondly, by a steric effect of the bulky carborane moiety. Although it may appear that the isolated yields are not high, conversions were in the range of ~50%. Isolation and purification of the products was a tedious task and the isolated yields we obtained represent the amounts of

Anion receptors containing thiazine-1,1-dioxide heterocycles as hydrogen bond donors

• Hong-Bo Wang,
• James A. Wisner and
• Michael C. Jennings

Beilstein J. Org. Chem. 2010, 6, No. 50, doi:10.3762/bjoc.6.50

• demands of the terminal phenyl rings in the two different receptor geometries despite the similar character of their central binding clefts. The steric effect of these rings in receptor 1 generates significant selectivity by the receptor for chloride versus the other, larger anions studied. The

Chemical aminoacylation of tRNAs with fluorinated amino acids for in vitro protein mutagenesis

• Shijie Ye,
• Allison Ann Berger,
• Dominique Petzold,
• Oliver Reimann,
• Benjamin Matt and
• Beate Koksch

Beilstein J. Org. Chem. 2010, 6, No. 40, doi:10.3762/bjoc.6.40

• the preparation of caged proteins. Fluorine is the most electronegative element and has a van der Waals radius of 1.47 Å [10]. Thus, substitution of a C–H bond with a C–F bond dramatically changes the electronic properties of the given molecule but exerts only a minor steric effect [11]. Due to the

• considerably the reactivity of both the amino and carboxylic groups; there is also a steric effect in this case. The amino group of α-(Tfm)Ala is generally protected by treatment with highly reactive mixed anhydrides or acid chlorides [28]. Thus, the N-(4-pentenoyl)-α-(Tfm)Ala was synthesized by means of 4

Molecular recognition of organic ammonium ions in solution using synthetic receptors

• Andreas Späth and
• Burkhard König

Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32

• -ring structure surrounding the ammonium ion was formed by the acyclic methylated pentasaccharide in the complexation. The chiral discrimination was ascribed to the steric effect of the fructofuranose rings of the pentasaccharide and the substituent of a given amino acid ester salt (complexation-induced

The role of an aromatic group in remote chiral induction during conjugate addition of α-sulfonylallylic carbanions to ethyl crotonate

• Shlomo Levinger,
• Ranjeet Nair and
• Alfred Hassner

Beilstein J. Org. Chem. 2008, 4, No. 32, doi:10.3762/bjoc.4.32

• increase in diastereoselectivity for the more electron deficient nitro derivative 1c. The most remarkable case of remote chirality transfer (over 99% dr), was observed for the 9-anthryl case 1h, which showed a rate enhancement as well [15][16]. In order to determine whether an unusual steric effect may