Synthesis and highly efficient light-induced rearrangements of diphenylmethylene(2-benzo[b]thienyl)fulgides and fulgimides

• Vladimir P. Rybalkin,
• Sofiya Yu. Zmeeva,
• Lidiya L. Popova,
• Valerii V. Tkachev,
• Andrey N. Utenyshev,
• Olga Yu. Karlutova,
• Alexander D. Dubonosov,
• Vladimir A. Bren,
• Sergey M. Aldoshin and
• Vladimir I. Minkin

Beilstein J. Org. Chem. 2020, 16, 1820–1829, doi:10.3762/bjoc.16.149

• -yl)-9-phenyl-3a,4-dihydronaphtho[2,3-c]furan-1,3-dione with cis-configuration of hydrogen atoms C(4)H and C(5)H. Two doublet signals of these protons at 4.49 and 5.37 ppm with characteristic spin–spin coupling constant J = 7.3 Hz are observed in the 1H NMR spectrum [24]. The photoinduced

• –spin coupling constant J = 7.3 Hz at 4.54 and 5.52 ppm, respectively, and of trans-3a,4-protons with a spin–spin coupling constant J = 15.4 Hz at 4.26 and 4.54 ppm, respectively. Similar to the initial fulgides, irradiation of acetonitrile solutions of fulgimides 4E and 8E with the light of 365 nm

• ). Irradiation of an acetonitrile solution of fulgide 7E with light of 365 nm gives rise to its decoloration brought about by the formation of a mixture of ring-closed diastereomers cis-10C (82%) and trans-10C (18%) (Scheme 5, Figure 6). The 1H NMR spectra of 10C contain signals of cis-3a,4-protons with a spin

Synthesis of ([1,2,4]triazolo[4,3-a]pyridin-3-ylmethyl)phosphonates and their benzo derivatives via 5-exo-dig cyclization

• Aleksandr S. Krylov,
• Artem A. Petrosian,
• Julia L. Piterskaya,
• Nataly I. Svintsitskaya and
• Albina V. Dogadina

Beilstein J. Org. Chem. 2019, 15, 1563–1568, doi:10.3762/bjoc.15.159

• coupling constant of 2JНР ≈ 20 Hz. In the 13С NMR spectra, the methylene carbon resonated as a doublet at δ 23.5 ppm (JCP = 143 Hz). In addition, the structures of triazolopyridines 3–8 were unambiguously confirmed by the crystal structure of 5b. Remarkably, the presence of a nitro group in the pyridine

• . Chemical shifts of the phosphorus nucleus for compounds 3–8 were registered in the range of δP 22–23 and 18–19 ppm for dimethyl а and diisopropyl phosphonates b, respectively. In the 1Н NMR spectra of products 3–8, the methylene unit was recorded as a doublet signal (δH 3.42–4.19 ppm) with a spin–spin

Conformational impact of structural modifications in 2-fluorocyclohexanone

• Francisco A. Martins,
• Josué M. Silla and
• Matheus P. Freitas

Beilstein J. Org. Chem. 2017, 13, 1781–1787, doi:10.3762/bjoc.13.172

• the electronic delocalization energies, as well as the Lewis (steric and electrostatic interactions) and non-Lewis (electron delocalization) contributions through the NOSTAR keyword. Chemical shifts and spin–spin coupling constant calculations were also performed at the ωB97X-D/6-311+g(d,p) level. All

Conformational study of L-methionine and L-cysteine derivatives through quantum chemical calculations and ³J_HH coupling constant analyses

• Weslley G. D. P. Silva,
• Carolyne B. Braga and
• Roberto Rittner

Beilstein J. Org. Chem. 2017, 13, 925–937, doi:10.3762/bjoc.13.94

• , experimental NMR spectroscopy measurements and spin-spin coupling constant (3JHH) calculations were performed. The experimental 1H NMR data for 1 (Table 3) indicate that the 3JHaHb1 and 3JHaHb2 coupling constants are almost constant in the studied solvents, supporting our findings through theoretical

• on the dihedral angle H−C−C−H, according to the well-known Karplus relationship [25]. As the observed 3JHH,obs coupling constant represents a weighted average of the contribution of each conformer, the calculated 3JHH,calc spin−spin coupling constant represents the individual 3Ji coupling constant

Investigation of the role of stereoelectronic effects in the conformation of piperidones by NMR spectroscopy and X-ray diffraction

• Cesar Garcias-Morales,
• David Ortegón-Reyna and
• Armando Ariza-Castolo

Beilstein J. Org. Chem. 2015, 11, 1973–1984, doi:10.3762/bjoc.11.213

• –H(7)eq), a type of hyperconjugative interaction. Keywords: NMR spectroscopy; piperidone; spin–spin coupling constant; stereoelectronic effect; X-ray diffraction structure; Introduction Stereoelectronic effects have attracted the attention of many researchers with an interest in organic chemistry

• →σ*, σ→π*, nx→σ*, nx→π*, hyperconjugation, and homohyperconjugative interactions significantly affect the Fermi contact contribution to the scalar spin–spin coupling constant. Therefore, the C–H coupling constants were used to investigate the stereoelectronic effects [64][65]. The main interactions

Conformational analysis and intramolecular interactions in monosubstituted phenylboranes and phenylboronic acids

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

Beilstein J. Org. Chem. 2013, 9, 1127–1134, doi:10.3762/bjoc.9.125

• the AIMAll program [29]. Finally, spin–spin coupling constant calculations were performed at the BHandH/EPR-III level in order to check for possible intramolecular hydrogen bonds through 1hJF,H(O) and the nF→pB interaction through 1TSJF,B in 2-fluorophenylboronic acid. 2- and 4-fluorophenylboronic