Cation-exchange resins as heterogeneous catalysts for the synthesis of 1,3-butadiene from propylene and formaldehyde

The possibility of using the cation-exchange resin Lewatit K2420 as a catalyst for the synthesis of 1,3-butadiene from isopropyl alcohol and formaldehyde solution in one technological stage has been shown. The regularities of the process have been established and the influence of the formaldehyde form (a cyclic trimer 1,3,5-trioxane and a 37% solution in water) on the composition of the reaction mass and the yield of the main and by-products has been assessed. It has been shown that the Lewatit K2420 heterogeneous catalyst showed catalytic activity in all reactions occurring in the synthesis of 1,3-butadiene, including the decomposition of 1,3,5-trioxane, dehydration of isopropyl alcohol into propylene, condensation of propylene and formaldehyde, dehydration of 3-butene-1-ol, decomposition of 4-methyl-1,3-dioxane, etc.

Cyclic butadiyne-linked porphyrin(2.1.2.1) oligomers

Cyclic butadiyne-linked porphyrin(2.1.2.1) oligomers are synthesized from 5,16-diethynylporphyrin(2.1.2.1) by Glaser–Hay coupling. Porphyrin(2.1.2.1) forms a bent structure which gives advantages for making cyclic structure without templating molecules. We isolated cyclic trimer and tetramer and characterized them by MALDI-TOF-MS and [Formula: see text]H NMR spectroscopy, theoretical calculations, UV-vis absorption and fluorescence spectra and cyclic voltammetry. The cyclic structure mainly affects the reduction potentials because of expansion of [Formula: see text]-conjugations through butadiyne-linkages to stabilize their LUMOs.

Conformationally supple glucose monomers enable synthesis of the smallest cyclodextrins

Cyclodextrins (CDs) are cyclic oligomers of α-1,4-d-glucopyranoside and are known mainly as hexamers to octamers. The central cavities of CDs can retain small molecules, enabling diverse applications. The smallest members, CD3 and CD4, have ring sizes too small to permit the most stable conformations of glucopyranose and have not been accessible synthetically. In this study, we present methods to chemically synthesize both CD3 and CD4. The main factor in the successful synthesis is the creation of a glucopyranose ring conformationally counterbalanced between equatorial- and axial-rich forms. This suppleness is imparted by a bridge between O-3 and O-6 of glucose, which enables the generation of desirable, albeit deformed, conformers when synthesizing the cyclic trimer and tetramer.

Steric group enforced aromatic cyclic trimer conformer in tripodal molecules

A family of tripodal molecules (1–6) with/without steric ethyl groups at the central benzene scaffold and with furan/thiophene/pyridyl groups at the 2-position of the benzimidazolyl unit was synthesised.

Crystal structure of cyclic tris(ferrocene-1,1′-diyl)

The molecular structure of the trinuclear title compound, [Fe3(C10H8)3] {systematic name: tris[μ-(η5:η5)-1,1′-bicyclopentadienyl]triiron(II)}, consists of three ferrocene subunits (each with an eclipsed conformation) that are condensedviaC—C bonds of the fulvalene moieties into a cyclic trimer. The angles between the planes of the cyclopentadienyl (Cp) rings within the three fulvalene moieties are 76.1 (3), 80.9 (3) and 81.7 (3)°. In the crystal, C—H...π interactions between neighbouring molecules lead to the cohesion of the structure.