Conformational equilibrium in supramolecular chemistry: Dibutyltriuret case

• Karina Mroczyńska,
• Małgorzata Kaczorowska,
• Erkki Kolehmainen,
• Ireneusz Grubecki,
• Marek Pietrzak and
• Borys Ośmiałowski

Beilstein J. Org. Chem. 2015, 11, 2105–2116, doi:10.3762/bjoc.11.227

• benzoates 2–9 Since 1 exists in a dynamic equilibrium at rt it was reasonable to associate 1 with anionic counterparts with their properties tuned systematically to the substituent effect. The association constants (Kassoc) are collected in Table 1 (see Supporting Information File 1 for figures). Usually

• bonding. Substituent effect on association Recently we have observed the correlation of the Kassoc and substituent constant in supramolecular complexes [10]. The lack of such correlation for complex of 1 with benzoates may be explained by a) multiple equilibrium (rotamerism in 1) and b) opposite effects

• of the substituent on complexes stability (further discussion in Supporting Information File 1). The use of substituted benzoate salts gave a set of points shown in Figure 6. It is easy to see that the substituent effect on chemical shift is not as high as before (compare difference in CIS values in

Synthesis and characterization of pH responsive D-glucosamine based molecular gelators

• Navneet Goyal,
• Hari P. R. Mangunuru,
• Bargav Parikh,
• Sonu Shrestha and
• Guijun Wang

Beilstein J. Org. Chem. 2014, 10, 3111–3121, doi:10.3762/bjoc.10.328

• ]. Previously we mostly focused on the modification of the C-2 position of the benzylidene acetal protected headgroups 1 and 2 (Figure 1). We obtained the general structural requirements for acyl derivatives at the 2-position. In this study, we explore the substituent effect at the benzylidene acetal protective

The unexpected influence of aryl substituents in N-aryl-3-oxobutanamides on the behavior of their multicomponent reactions with 5-amino-3-methylisoxazole and salicylaldehyde

• Volodymyr V. Tkachenko,
• Elena A. Muravyova,
• Sergey M. Desenko,
• Oleg V. Shishkin,
• Svetlana V. Shishkina,
• Dmytro O. Sysoiev,
• Thomas J. J. Müller and
• Valentin A. Chebanov

Beilstein J. Org. Chem. 2014, 10, 3019–3030, doi:10.3762/bjoc.10.320

• rise either to pyrazolopyridine or pyrazolopyrimidine heterocycles. In the authors' opinion, the different outcomes in three-component reactions involving 3-methyl- or 3-aryl-substituted 5-aminopyrazoles can mainly be put down to the steric substituent effect [11]. It is noteworthy to mention that

P(O)R₂-directed Pd-catalyzed C–H functionalization of biaryl derivatives to synthesize chiral phosphorous ligands

• Rong-Bin Hu,
• Hong-Li Wang,
• Hong-Yu Zhang,
• Heng Zhang,
• Yan-Na Ma and
• Shang-dong Yang

Beilstein J. Org. Chem. 2014, 10, 2071–2076, doi:10.3762/bjoc.10.215

• chiral [1,1'-binaphthalen]-2-yldiphenylphosphine oxide as a substrate [35]. In the process of alkenylation and acetoxylation, the corresponding products 2a and 2b were obtained in moderate yields and high enantioselectivities. Next, we examined the substituent effect with P(O)(p-Tol)2 as a directing

Practical synthesis of indoles and benzofurans in water using a heterogeneous bimetallic catalyst

• Cybille Rossy,
• Eric Fouquet and
• François-Xavier Felpin

Beilstein J. Org. Chem. 2013, 9, 1426–1431, doi:10.3762/bjoc.9.160

• pronounced N-substituent effect was observed with hexyne as coupling partner, where the tosyl protecting group gave the best result. These results strongly suggest that both electronic and steric factors participate in the cyclization step. With these optimized conditions in hand, we next focused on the

Substituent effect on the energy barrier for σ-bond formation from π-single-bonded species, singlet 2,2-dialkoxycyclopentane-1,3-diyls

• Jianhuai Ye,
• Yoshihisa Fujiwara and
• Manabu Abe

Beilstein J. Org. Chem. 2013, 9, 925–933, doi:10.3762/bjoc.9.106

• entropy effect were found to play crucial roles in increasing the lifetime. Keywords: laser flash photolysis; lifetime; singlet diradicals (biradicals); substituent effect; π-single bond; Introduction Localized singlet diradicals are key intermediates in processes involving the homolytic bond-cleavage

• substituent effect using the sterically bulky group is effective to prolong the lifetime of the singlet diradicals. Conclusion We have succeeded in generating long-lived singlet diradical species DRc–g, τ293 = 580–5394 ns, which were much longer-lived species than DRa (τ293 = 299 ns). It was found that the

Translation of microwave methodology to continuous flow for the efficient synthesis of diaryl ethers via a base-mediated S_NAr reaction

• Charlotte Wiles and
• Paul Watts

Beilstein J. Org. Chem. 2011, 7, 1360–1371, doi:10.3762/bjoc.7.160

• towards the SNAr reaction between DCNB (4) and 4-methoxyphenol (5) (residence time = 30 s; reactor temperature = 195 °C). Illustration of the substituent effect on the synthesis of diaryl ethers under continuous flow (residence time = 30 s; reactor temperature = 195 °C). Schematic illustrating the mixing

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

• ] was previously contrasted against a cumulative acceleration by methyl substituents upon the rate of reaction with ArSCl; the substituent effect comparison was not extended beyond methyl, so this has no bearing on the effects of branching. Nevertheless, this difference agrees with the different number

Heavy atom effects in the Paternò–Büchi reaction of pyrimidine derivatives with 4,4’-disubstituted benzophenones

• Feng-Feng Kong,
• Jian-Bo Wang and
• Qin-Hua Song

Beilstein J. Org. Chem. 2011, 7, 113–118, doi:10.3762/bjoc.7.16

• in Table 1. The substituent effect of benzophenones on the regioselectivity (2/3) is similar to our previous observations [10], a gradual decrease according to their electronic effect from 1a to 1e. In our previous papers [10][13], the photochemical [2 + 2] cycloadditions of DMT and DMU with

• is not responsible for the low yields. Therefore, the effect of halo-substituted benzophenones on the Paternò–Büchi reaction is not a “pure” substituent effect. Temperature effects In our previous papers [9][11], the photochemical [2 + 2] cycloadditions of DMT/DMU with benzophenones revealed notable

The allylic chalcogen effect in olefin metathesis

• Yuya A. Lin and
• Benjamin G. Davis

Beilstein J. Org. Chem. 2010, 6, 1219–1228, doi:10.3762/bjoc.6.140

• . Keywords: allyl substituent effect; allyl sulfides; aqueous chemistry; olefin metathesis; protein modifications; Review Olefin metathesis is one of the most useful chemical transformations for forming carbon–carbon bonds in organic synthesis (Scheme 1) [1][2][3][4]. The broad utility of olefin metathesis

• to afford 12a with a yield of only 32%. With the substituted allyl ethers 11c and 11d, reduction in yield was observed with increasing bulk of the protecting group (44% and 7%, respectively). Taking advantage of the allylic hydroxyl substituent effect, the authors synthesized (+)-isofagomine with the

Redox-active tetrathiafulvalene and dithiolene compounds derived from allylic 1,4-diol rearrangement products of disubstituted 1,3-dithiole derivatives

• Filipe Vilela,
• Peter J. Skabara,
• Christopher R. Mason,
• Thomas D. J. Westgate,
• Asun Luquin,
• Simon J. Coles and
• Michael B. Hursthouse

Beilstein J. Org. Chem. 2010, 6, 1002–1014, doi:10.3762/bjoc.6.113

• the 1,4-shift products. It is also unusual that the sole product from the corresponding 2-methoxyphenyl compound leads to a dihydrofuran derivative, particularly since the electron donating substituent effect should be identical to that of the 4-methoxy compound, which rearranges to give the

Tether- directed synthesis of highly substituted oxasilacycles via an intramolecular allylation employing allylsilanes

• Peter J. Jervis and
• Liam R. Cox

Beilstein J. Org. Chem. 2007, 3, No. 6, doi:10.1186/1860-5397-3-6

• accommodated. In light of the interesting substituent effect on 1,4-induction, we were keen to investigate how incorporating additional substituents into the substrate might influence the stereoselectivity of the reaction. Specifically we wanted to assess how incorporating an additional methyl group α to the

Effect of transannular interaction on the redox- potentials in a series of bicyclic quinones

• Grigoriy Sereda,
• Jesse Van Heukelom,
• Miles Koppang,
• Sudha Ramreddy and
• Nicole Collins

Beilstein J. Org. Chem. 2006, 2, No. 26, doi:10.1186/1860-5397-2-26

• calculated LUMO+1 energies. As opposed to the LUMO orbitals, the LUMO+1 orbital coefficients are weighted significantly on the non-quinone part of the bicyclic system. This accounts for: (1) significantly larger substituent effect on the second redox-potentials, than on the first redox-potentials; (2) lack

• redox-potentials correlate with calculated LUMO+1 energies. As opposed to the LUMO orbitals, the LUMO+1 orbital coefficients are weighted significantly on the non-quinone part of the bicyclic system. This accounts for: (1) significantly larger substituent effect on the second redox-potentials, than on