21388-97-6Relevant articles and documents
Conformational folding induced by π-π interaction in a series of flexible dyads consisting of isomeric mesoporphyrin nitrobenzyl esters
Colominas, Carles,Eixarch, Lisbeth,Fors, Pere,Lang, Kamil,Nonell, Santiago,Teixido, Jordi,Trull, Francesc R.
, p. 997 - 1004 (1996)
A series of isomeric (ortho, meta and para) nitrobenzyl mono- and di-esters of mesoporhyrin, in which the nitrobenzyl group(s) is (are) mono-linked through one or both propionate chains of the porphyrin, have been synthesized and their room-temperature conformations in a number of solvents have been investigated using 1H NMR spectroscopy and theoretical calculations. Folding of these flexible dyads is consistent with the following observations: (1) 1H NMR ring current upfield shift in all solvents assayed [i.e., CDCl3, CDCl3-CD3OD (10:1) and C 6D6] of 0.5-2.5 ppm for the aryl protons; (2) these shifts are independent of temperature over the range 25 to -55°C; (3) the 1H NMR resonance values of mesoporphyrin benzyl ester (lacking the nitro group) are not shifted, indicating a preferred, sterically less crowded, extended conformation. The presence of the nitro group on the phenyl ring(s) is responsible for the folding of these flexible dyads, and the results can be interpreted in terms of π-π interactions (C. A. Hunter and J. K. M. Sanders, J. Am. Chem. Soc., 1990, 112, 5525-5534) between the two halves. In the theoretically calculated (molecular mechanics and semiempirical calculations) minimum-energy folded conformations, each benzyl group lies approximately parallel to the porphyrin π-system with its centre slightly offset relative to the centre of the porphyrin; however, for each isomer, significant structural differences between the ortho isomer and its meta and para counterparts are found. The implications of these differences for the photoinduced electron transfer efficiencies in these dyads are discussed.
4-Imidazol-1-yl-butane-1-sulfonic acid ionic liquid: Synthesis, structural analysis, physical properties and catalytic application as dual solvent-catalyst
Khaligh, Nader Ghaffari,Mihankhah, Taraneh,Johan, Mohd Rafie,Juan, Joon Ching
, p. 866 - 878 (2019/07/12)
4-Imidazol-1-yl-butane-1-sulfonic acid (ImBu-SO3H) has been successfully synthetized and fully characterized by FT-IR and high-resolution NMR spectroscopy (1H, 13C). The “plausible” alternative structures of ImBu-SO3H were discussed on the basis of its NMR data. The ionic liquid showed interesting dual solvent-catalyst property, which was studied experimentally for the acetylation of a variety of functionalized alcohols, phenols, thiols, amines and α-tocopherol (α-CTP) as the most active form of vitamin E with acetic anhydride and which provided good yields within a short reaction time. ImBu-SO3H was successfully recycled by product extraction with an average recovered yield of 82% for 5 subsequent runs. The catalytic activity of the recycled ImBu-SO3H showed almost no loss even after five consecutive runs.
Doping of copper (I) oxide onto a solid support as a recyclable catalyst for acetylation of amines/alcohols/phenols and synthesis of trisubstituted imidazole
Gupta, Manjulla,Gupta, Monika
, p. 231 - 241 (2016/01/09)
A study of copper-mediated C-heteroatom especially C-N and C-O bond formations using simpler methodologies has been carried out. In the present work, acetylation of various substrates such as amines, phenols and alcohols; synthesis of 2,4,5-trisubstituted imidazole is done using simple and easily available starting materials. Copper (I) oxide was synthesized in situ by the reduction of Fehling's solution with glucose followed by its anchoring onto different supports like silica, HAP, basic alumina and cellulose. Comparison and contrasts between the reactivity of copper (I) oxide supported onto different supports for these reactions are made. The reactivity of copper (I) oxide seems to be largely dependent on the nature of support and the most active catalyst for a particular reaction was further characterized by different spectroscopic techniques such as FTIR, XRD, TGA, XPS, SEM, TEM and AAS. The catalysts were found to be stable, easily recyclable without any significant loss in activity. Graphical abstract: Applications of solid supported copper (I) oxides (where solid support is silica, HAP, cellulose and basic alumina) are studied for various organic transformations with special emphasis on C-N and C-O bond formation reactions.[Figure not available: see fulltext.]
