Synthesis and crystal structures of 5,17-di-bromo-26,28-dihy-droxy-25,27-dipropynyloxycalix[4]arene, 5,17-di-bromo-26,28-dipropoxy-25,27-dipropynyloxycalix[4]arene and 25,27-bis-(2-azido-eth-oxy)-5,17-di-bromo-26,28-di-hydroxy-calix[4]arene

The calixarenes, 5,17-di-bromo-26,28-dihy-droxy-25,27-dipropynyloxycalix[4]arene (C34H26Br2O4, 1), 5,17-di-bromo-26,28-dipropoxy-25,27-dipropynyloxycalix[4]arene (C40H38Br2O4, 2) and 25,27-bis-(2-azido-eth-oxy)-5,17-di-bromo-26,28-di-hydroxy-calix[4]arene (C32H28Br2N6O4, 3) possess a pinched cone mol-ecular shape for 1 and 3, and a 1,3-alternate shape for compound 2. In calixarenes 1 and 3, the cone conformations are additionally stabilized by intra-molecular O-H⋯O hydrogen bonds, while in calixarene 2 intra-molecular Br⋯Br inter-actions consolidate the 1,3-alternate mol-ecular conformation. The dense crystal packing of the cone dialkyne 1 is a consequence of π-π, C-H⋯π and C-H⋯O inter-actions. In the crystal of the diazide 3, there are large channels extending parallel to the c axis, which are filled by highly disordered CH2Cl2 solvent mol-ecules. Their contribution to the intensity data was removed by the SQUEEZE procedure that showed an accessible void volume of 585 Å3 where there is room for 4.5 CH2Cl2 solvent mol-ecules per unit cell. Rigid mol-ecules of the 1,3-alternate calixarene 2 form a columnar head-to-tail packing parallel to [010] via van der Waals inter-actions, and the resulting columns are held together by weak C-H⋯π contacts.

Dual Brønsted acidic-basic function immobilized on the 3D mesoporous polycalix [4]resorcinarene: As a highly recyclable catalyst for the synthesis of spiro acenaphthylene/indene heterocycles

In this study, a novel dual Brønsted acidic-basic nano-scale porous organic polymer catalyst, PC4RA@SiPr-Pip-BuSO3H, was synthesized through various steps: preparation of a 3D network of polycalix, modification with (3-chloropropyl)-trimethoxysilane, then functionalization of polymer with piperazine and n-butyl sulfonic acid under the provided conditions. The catalyst characterization was performed by FT-IR, TGA, EDS, elemental mapping, PXRD, TEM, and FE-SEM analyses, confirming high chemical stability, activity, recoverability, and excellent covalent anchoring of functional groups. So, the designed catalyst was utilized for preparing spiro-acenaphthylene and amino-spiroindene heterocycles, providing good performance with a high yield of the corresponding products. Accordingly, this catalyst can be used in different organic transformations. Necessary experiments were conducted for the recyclability test of the polymeric catalyst, and the results showed the PC4RA@SiPr-Pip-BuSO3H catalyst can be reused 10 times without any decrease in its activity or quality with excellent stability. The structure of resultant spiro heterocycles was confirmed using 1H NMR, 13C NMR, and FT-IR.

Tungstic acid-functionalized polycalix[4]resorcinarene as a cavity-containing hyper-branched supramolecular and recoverable acidic catalyst in 4H-pyran synthesis

In this study, tungstic acid immobilized on polycalix[4]resorcinarene, PC4RA@SiPr-OWO3H, as a mesoporous acidic solid catalyst was synthesized and investigated for its catalytic activity. Polycalix[4]resorcinarene was prepared via a reaction between formaldehyde and calix[4]resorcinarene, and then the resulting polycalix[4]resorcinarene was modified using (3-chloropropyl)trimethoxysilane (CPTMS) to obtain polycalix[4]resorcinarene@(CH2)3Cl that was finally functionalized with tungstic acid. The designed acidic catalyst was characterized by various methods including FT-IR spectroscopy, energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), elemental mapping analysis and transmission electron microscopy (TEM). The catalyst efficiency was evaluated via the preparation of 4H-pyran derivatives using dimethyl/diethyl acetylenedicarboxylate, malononitrile, and beta-carbonyl compounds, confirmed by FT-IR spectroscopy and 1H and 13C NMR spectroscopy. The synthetic catalyst was introduced as a suitable catalyst with high recycling power in 4H-pyran synthesis.

Triazolated calix[4]semitubes: assembling strategies towards long multicalixarene architectures

Cone and 1,3-alternate calix[4]arenes bearing pairs of 2-azidoethyl or propargyl groups, and 1,3-alternate calix[4]arenes having four 2-azidoethyl, four propargyl groups or pairs of 2-azidoethyl and silylated propargyl groups were explored...

Inherently dinuclear iridium(III) meso architectures accessed by cyclometalation of calix[4]arene-based bis(aryltriazoles)

Conventional cyclometalation of calix[4]arene bis(aryltriazoles) with iridium(III) chloride hydrate leads to unique meso architectures in which the Ir₂Cl₂ core is cross-bound by two (C^N)₂ ligands, which allows further replacement of the chloride bridges with ancillary ligands while maintaining the dinuclear structures of the complexes having independent or coupled iridium pairs.