Synthesis of a polymer-supported oxazolidine aldehyde for asymmetric chemistry

An expedient synthesis of the polymer-supported aldehyde 3, as a Garner aldehyde equivalent, is described. Oxazolidine 3 may be obtained through preformation of aldehyde linker 4 in solution and loaded onto amine-terminating resin under peptide-coupling conditions, or alternatively via oxidation of polymer-bound alcohol 14. The integrity of the serine-derived stereocenter is maintained through all steps of the synthesis.     

Enhanced cooperative binding of oligonucleotides to form DNA duplexes mediated by metal ion chelation

Metal chelating iminodiacetic acid moieties were appended to abutting ends of two 9-mer oligonucleotides designed to hybridize contiguously on an 18-mer target. Chelation of 1 equivalent of Gd3+ cooperatively increases affinities of the oligonucleotides to the single stranded DNA target as evidenced by a 15 degrees C increase in Tm of the complex.     

Kinetic modeling of liquid-phase esterification of acetic acid with n-butanol using heterogeneous poly(o-methylene p-toluene sulfonic acid) as catalyst

Liquid-phase esterification of acetic acid with n-butanol to n-butyl acetate is studied in the presence of a polymeric catalyst, that is, poly(o-methylene p-toluene sulfonic acid). The performance of the proposed catalyst is compared with the other commercially available homogeneous and heterogeneous catalysts in terms of its activity. Experiments are conducted in an isothermal stirred batch reactor to study the effects of speed of agitation, temperature, and catalyst loading on the rate of reaction. A concentration-based pseudo-homogeneous (PH) kinetic model and activity-based kinetic models such as PH, Eley-Rideal (ER), and Langmuir-Hinselwood-Hougen-Watson (LHHW) models are developed. All the models considered in this study resulted in similar percentage deviation close to 4%. Further, kinetic models are validated through additional experiments, and it is observed that the simple concentration-based PH model is able to predict experimental data with least deviation compared to activity-based PH, ER, and LHHW models. The developed kinetic models are also tested using the Fisher-Snedecor test (F-test) and are found to be acceptable. By incorporating both modeling data and validation data, the overall absolute average deviations of different models are found to be concentration-based PH model 4.354%, activity-based PH model 5.006%, ER I model 5.189%, ER II model 5.403%, ER III model 5.437%, and LHHW model 6.104%, illustrating the superiority of the simple concentration-based PH model.     

PNA forms an i-motif

A C-rich PNA hexanucleotide, p(C5T), has been shown to form an i-motif by nanoelectrospray ionization mass spectrometry coupled with H/D exchange, to have thermal stability comparable with its DNA analogue, but to exist over a much narrower pH range.     

Structural Investigations on 4-Chloro-6-Phenyl-7,8,9,14-Tetrahydroquinolino [2′,3′:7,6]cyclohept[<Emphasis Type=Italic>b</Emphasis>]indoles

Abstract  

Several 4-chloro-6-phenyl-7,8,9,14-tetrahydroquinolino[2′,3′:7,6]cyclohept[b]indole derivatives were obtained in one pot synthesis reactions via acid catalyzed condensation and cyclization of 1-oxo-1,2,3,4,5,10-hexahydrocyclohept[b]indoles with 2-amino-5-chlorobenzophenone in glacial acetic acid. Parent 4-chloro-6-phenyl-7,8,9,14-tetrahydroquinolino[2′,3′:7,6]cyclohept[b]indole and the 10, 11, 12 and 13-methyl derivatives all crystallize in the triclinic space group P[`1] overline{1} . The 11-methyl derivative crystallizes with Z′ = 2, the 10 and 12-methyl isomers cocrystallize as a solid solution of the two molecules, and the 13-methyl derivative and the parent compound each with Z′ = 1. The unit cell parameters for the four structures are a = 10.1826(8), b = 12.3918(7), c = 16.3825(8)?, α = 91.626(1), β = 95.718(1), γ = 94.966(1)° and V = 2,047.7(2) ?³ for the 11 methyl derivative; a = 10.168(2), b = 10.304(2), c = 10.610(2)?, α = 89.169(3), β = 87.774(3), γ = 63.726(2)° and V = 996.0(3) ?³ for the solid solution of the 10 and 12-methyl derivative, a = 9.0412(5), b = 10.4926(6), c = 10.9093(6)?, α = 94.482(1), β = 102.181(1), γ = 95.812(1)° and V = 1,001.13(10) ?³ for the 13-methyl compound, and a = 9.6463(6), b = 10.2395(6), c = 10.6062(6)?, α = 91.7263(8), β = 94.7200(8), γ = 114.0812(7)° and 950.85(10) ?³ for the unsubstituted parent compound. The molecular shape of the molecules is not affected by the substitution pattern and all molecules exhibit the same conformation with very similar geometries. Intermolecular interactions are limited to weak C–H···Cl hydrogen bonds, a small number of π···π stacking interactions and several C–H···π interactions, which, in combination with shape recognition, dominate the packing of the quinolinocyclohept[b]indoles.     

InCl3-catalyzed four-component reaction: a novel synthesis of N-carbazolyl dihydropyridines

We have developed a simple, efficient, and environmentally benign microwave-assisted InCl₃-catalyzed synthesis of N-carbazolyldihydropyridines via a four-component reaction of 3-amino-9-ethylcarbazole, malononitrile, aromatic aldehydes, and acetylenic esters. The use of microwave heating allowed for reduced reaction times and resulted in higher yields. This four-component reaction is atom-efficient, high-yielding, and applicable to a wide variety of four-component reactions.     

Microwave assisted synthesis of indolo[2,3-b]dibenzo[b,g][1,8]naphthyridines

We have developed an effective microwave assisted p-TsOH catalyzed synthesis of indolo[2,3-b]dibenzo[b,g][1,8]naphthyridines via a one pot reaction of 3-amino-9-ethylcarbazole and 2-chloro-3-formylquinolines.     

Recent studies on small molecular and polymeric hole-transporting materials for high-performance perovskite solar cells

A decade of significant research has led to the emergence of photovoltaic solar cells based on perovskites that have achieved an exceptionally high-power conversion efficiency of 26.08%. A key breakthrough in perovskite solar cells (PSCs) occurred when solid hole-transporting materials (HTMs) replaced liquid electrolytes in dye-sensitized solar cells (DSSCs), because HTMs play a crucial role in improving photovoltaic performance as well as cell stability. This review is mainly focused on the HTMs that are responsible for hole transport and extraction in PSCs, which is one of the crucial components for efficient devices. Here, we have reviewed small molecular as well as polymeric HTMs that have been reported in the last two years and discussed their performance based on the analysis of their molecular architectures. Finally, we include a perspective on the molecular engineering of new functional HTMs for highly efficient stable PSCs.