Synthesis and structure of [2-oxo(thioxo)tetrahydropyrimidin-4-yl]calix[4]arenes

Cone-shaped di- and tetrapropoxycalix[4]arenes functionalized at the upper rim with one or two 2-oxo(thioxo)tetrahydropyrimidine residues were synthesized by the Biginelli reaction of formylcalixarenes with urea (thiourea) and methyl acetoacetate. The steric structure of the products was studied by NMR and X-ray diffraction. The Biginelli reaction with dipropoxyformylcalixarene was diastereoselective, and it quantitatively produced the corresponding meso form. Tetrapropoxydiformylcalixarenes under analogous conditions gave rise to equimolar mixtures of racemic and meso compounds. The macrocyclic skeleton of the synthesized pyrimidine-containing calixarenes in crystal and in solution has a flattened cone conformation. (5-Methoxycarbonyl-2-oxotetrahydropyrimidin-4-yl)calixarene molecules in crystal undergo self-organization to form infinite chains via repeated inclusion of the methoxy group into the cavity of the neighboring macrocycle. Selforganization of bis(5-methoxycarbonyl-2-oxotetrahydropyrimidin-4-yl)calixarene with formation of analogous chains involves intermolecular hydrogen bonding NH ... O=C.     

Dimeric Capsules Formed by Tetra‐CMPO Derivatives of (Thia)Calix[4]arenes

Thiacalix[4]arene 2 , calix[4]arene 3 a and its tetraether fixed in the cone conformation 3 b form homo‐ and heterodimeric capsules in apolar solvents, which are held together by a seam of NH???O=P hydrogen bonds between carbamoylmethyl phospine oxide functions attached to their wide rim. Their internal volume of ～370 ų requires the inclusion of a suitable guest. Although neutral molecules such as adamantane (derivatives) or tetraethylammonium cations form kinetically stable complexes (¹H‐ and ³¹P‐time scale), the included solvent is rapidly exchanged. The internal mobility of the included tetraethylammonium cation is distinctly higher (ΔG=42.5 and 49.7 kJ mol^?1 for 3 a and 3 b ) than that for similar capsules of tetraurea calix[4]arenes 1 . Mixtures of 1 with 2 , 3 a , or 3 b contain only the two homodimers but the heterodimerization occurs with the tetraloop tetraurea 6 , which cannot form homodimers. Two dimers with cationic guests ( 2? (C₅H₅)₂Co⁺ ?2 and 3 a? Et₃NH⁺ ? H₂O ?3 a ) were confirmed by single‐crystal X‐ray analysis.     

Synthesis, Structure and Selective Upper Rim Functionalization of Long Chained Alkoxythiacalix[4]arenes

The synthesis and X-ray structure investigation of the cone shaped monodecyloxythiacalix[4]arene, as well as the introduction of the reactive bromide or chloromethyl groups on it’s upper rim are described. Preparation of the amphiphilic derivative of thiacalixarene bearing three hydrophilic diethoxyphosphoryl groups at the upper rim and lipophilic decyloxy group at the lower rim is presented.     

X-ray spectral and quantum chemical study of the electronic structure of thiacalix[4]-arenes and their acyclic analogs

An X-ray photoelectron and X-ray emission study of the charge state of thiacalix[4]arenes is performed with a comparison with the data of quantum chemical calculations. Relaxation corrections between the Kohn-Sham orbital energies calculated by the DFT method and experimental parameters of the X-ray emission and photoelectron spectra of the studied compounds are estimated. It is shown that the formation of a cyclic aromatic system in thiacalixarenes results in a decrease in the energy of orbitals involving p-π interactions of the bridging sulfur atoms and aromatic moieties, which determines the features of the X-ray emission spectra of the studied compounds.     

The structure of organophosphorus compounds. Part XLIII. The molecular structure of cis- and trans-λ3-amino-2,4,6 -tri(Tert-Butyl)Phenyliminophosphines

Part XLII, see ref. [1].     

Palladium(II) extraction by sulfur-containing calix[4,6]arenes from hydrochloric acid solutions

The comparison of the extraction properties of calixarenes, thiacalixarenes, and calix[4,6]arene thioethers showed that methyl(thiamethyl)calix[4,6]arenes 3a and 4a have the highest extraction abilities. These extractants rapidly and completely extract palladium from hydrochloric acid solutions; regarding distribution factors achieved in the kinetic mode, they three to four orders of magnitude exceed their monodentate analogue, octylbenzyl sulfide (OBnS). Approaches are considered to enhance palladium extraction via generating mixed palladium species in low-acidity solutions and via intramolecular catalysis by the protonated oxygen atoms of alkoxy groups in the lower rim. For 1 M HCl, the kinetic order of diluent effects on palladium extraction was established. The substitution of sulfur atoms for bridging CH₂ groups was discovered to enhance palladium extraction by calix[4]arene thioether 3c.     

Sterically overloaded γ3-aminoiminophosphines: Molecular structure and properties of N,N-bis (trimethylsilyl) amino-N′-[2,4,6-tri(t-butyl)phenyl]-iminophosphine

Conclusions X-ray crystallography has been used for the first time to examine the spatial structure of an acyclic compound containing two-coordinated phosphorus with the grouping NP=NAr-(N,N-bis (trimethylsilyl) amino-N-[2,4,6-tri(t-butyl)phenyl]aminophosphine. It has been found that the reduced reactivity of this compound towards proton-donor reagents, and its unusually low tendency to undergo dimerization, are due to the screening of the P=N bond by bulky substituents.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No, 6, pp. 1304–1308, June, 1987.     

Extraction of palladium with acyclic analogs of thiacalix[4]arenes from nitric acid solutions

p-tert-Butylcalix[4]arene was compared with its acyclic analogs in palladium extraction from nitric acid solutions as mononuclear and poly(bi)nuclear complexes with participation of protonated molecules of podands and macrocycle. The extraction ability of podands is similar to that of macrocycle because of the same character of complexation (Pd: S = 1: 1) without formation of new chelates and lower than that of monodentate analog owing to formation of a square complex (Pd: S = 1: 2).     

P-Functionalized λ3-Iminophosphines and Diphosphenes

Abstract

The synthesis of P-functionalized iminophosphines and diphosphenes is discussed. The reactivity and the coordination chemistry of selected compounds have been explored.