9 research outputs found
Nonoxidative Dimerization of 3,4-dioxygenated Cinnamates To Aryltetralin Lignans
No full textThe BF3 catalyzed dimerization of (E)-3,4-dimethoxycinnamic acid methyl ester offers a route to aryltetralin lignans. The mechanism of the reaction is discussed
SYNTHESIS OF C-ALKYL CALIX[4]ARENES .3. ACID-CATALYZED REARRANGEMENT OF 2,6-DIMETHOXYCINNAMATE PRIOR TO TETRAMERIZATION TO CALIX[4]ARENES
No full textIn our continuing studies concerning the versatility of the acid-catalyzed conversion of cinnamates to calix[4]resorcinarenes, we have demonstrated that 2,6-dimethoxycinnamic acid ethyl ester 3 undergoes an interesting rearrangement to afford the same calix[4]resorcinarenes as those obtained from the 2,4-dimethoxy isomer 1. The experimental results were substantiated by molecular mechanics calculations
A Novel Route To Calix[4]arenes .2. Solution-state and Solid-state Structural-analyses and Molecular Modeling Studies
No full textA versatile route to a series of C-alkylcalix[4]resorcinarenes has been developed, using 2,4-dimethoxycinnamates as starting materials under carefully controlled reaction conditions employing BF3 as a Lewis acid catalyst. Depending on the reaction conditions and the nature of the ester side chain in the cinnamates, the calixarenes can adopt 1,2-alternate, 1,3-alternate, or flattened-cone conformational states. An extensive study, relating to the influence of the Lewis acid, temperature, and reaction time, has provided information on the relative ratios of the different conformations and their interconversion. Structural assignments are based on detailed spectroscopic analyses including X-ray analyses. The latter provide evidence of their molecular structure and shape in the solid state. A detailed molecular modeling study has been completed and is described. From the data obtained, good agreement with NMR data, X-ray analyses and experimental results is observed
The tetramerization of 2,4-dimethoxycinnamates. A novel route to calixarenes
No full textTreatment of (E)-2,4-dimethoxycinnamic acid methyl ester with BF3.Et2O in CHCl3 at room temperature afforded in 75% yield two stereoisomeric C-alkylcalix[4]resorcinarenes, which were shown to be in the 1,2-alternate and flattened-cone configurations
Synthesis and Interaction with Copper(II) Cations of Cyano- and Aminoresorcin[4]arenes
No full textFollowing our studies on resorcin[4]arenes, we synthesized new macrocycles containing cyanomethyl and aminomethyl side chains. Three stereoisomers (2a-c) of the former were obtained by BF3·Et2O tetramerization of the corresponding trans-cinnamic acid derivative and were shown to be in the 1,2-alternate, cone, and 1,3-alternate conformations. Conversely, the tetraamino derivative 6a in the cone conformation was prepared from the corresponding tetrabromide 3a. The interactions with CuII cations of the new compounds were analyzed by measurements of 1H NMR and EPR spectra in parallel with molecular modeling calculations
Synthesis of Calix[4]arenes. 5. Design, Synthesis and Computational Studies of Chiral Amidoresorc[4]arenes
No full textTreatment of tetraaIcohol 1 with glutaroyl (2a, n = 3), adipoyl (2b, n = 4), and pimeloyl (2c, n = 5) dichlorides in the presence of Et(3)N gave the corresponding double-spanned calix[4]resorcarenes 3a-c, in which the insertion of two polymethylene bridges led to the formation of a cavity-shaped architecture resembling a basket. NMR, X-ray, and molecular dynamic-studies showed that one of the two equivalent flattened-cones, which constituted the original cone conformation of 1, had been frozen in the basket derivative. In the solid state the calixarene 3b exists as a supramolecular dimer, in which one of the handles is inserted in the concave cavity of an adjacent molecule. A molecular modeling study revealed that the minimum absolute free energy was associated to the unsymmetrical type of dimer named AB-AC
