Synthesis of mono-, di- and tetra-alkyne functionalized calix[4]arenes: Reactions of these multipodal ligands with dicobalt octacarbonyl to give complexes which contain up to eight cobalt atoms

Abstract

The functionalized mono-alkyne cone-monopropargyl p-tert-butylcalix[4]arene was synthesized by the reaction of p-tert-butylcalix[4]arene with K(2)CO(3) and 3-bromo-1-propyne. More prolonged reaction times led to the formation of the 1,3 cone bis(propargyl)calix[4]arene . The tetra-alkyne species cone-tetrapropargyl p-tert-butylcalix[4]arene and its conformational isomer, 1,3-alternate-tetrapropargylcalix[4]arene may both be prepared via related reaction sequences. The structures of the molecules and were both re-determined by single crystal X-ray diffraction studies. All four functionalized calixarenes react rapidly with dicobalt octacarbonyl to give [(calix[4]arene).{Co(2)(CO)(6)}(n)] species (n = 1, 2 or 4) in which the alkyne functionalities of the propargylcalix[4]arenes are ligated to one or more [Co(2)(CO)(6)] groups. Two products could be harvested from the reaction of [Co(2)(CO)(8)] with the bis-propargyl-calixarene , depending on the reaction conditions and relative molar quantities of the reactants: complex , [1,3-cone bis(propargyl)calix[4]arene.{Co(2)(CO)(6)}(2)], in which each alkyne group is bonded to a [Co(2)(CO)(6)] group, and complex , [1,3-cone bis(propargyl)calix[4]arene.{Co(2)(CO)(6)}], which contains a unligated alkyne and an alkyne group bonded to a Co(2)(CO)(6) unit. The structures of the tetracobalt and octacobalt complexes and were established by single crystal X-ray diffraction studies.

Achieving High Affinity towards a Bacterial Lectin through Multivalent Topological Isomers of Calix[4]arene Glycoconjugates

“…Molecular modelling studies were undertaken to assess the ability of the most efficient ligand, 29 to bind to two adjacent binding sites of the tetrameric lectin PA‐IL as postulated from ITC experiments. A three‐dimensional model of the tetravalent glycocluster 29 was built from the X‐ray crystal data of the tetrapropargylated calixarene 12 36. From conformational analysis and taking into account the flexibility of the linkers, the maximum distances between galactose residues (O‐4) were estimated to be 28 Å for branches on the same side of the calixarene scaffold and 39 Å for branches on opposite faces.…”

“…Modelling of glycocluster and PA‐IL : Construction of the core scaffold of glycocluster 29 was built by using the X‐ray structure of 12 36. Atomic partial charges were then calculated (MOPAC/MNDO).…”

Chiral Heteroditopic Baskets Designed from Triazolated Calixarenes and Short Peptides

“…The four propargylated calixarenes 3 – 6 were probed as the acetylene components for CuAAC reactions. These oligoalkynes are readily prepared from the parent p‐tert ‐butylcalix[4/6]arenes in one‐ (compounds 3 and 4 ) or two‐step (compounds 5 and 6 ) alkylation reactions. In contrast to the calixarenes 3 – 5 , which are pre‐organized in a cone conformation and maintain it even at prolonged heating required by the CuAAC reaction, the methylated/propargylated calix[6]arene 6 is conformationally flexible even at room temperature, but must adopt the flattened cone conformation stabilized by CH 3 ⋅⋅⋅π contacts upon extending the three propargyl units to bulkier triazole ones …”

Bifunctional Derivatives of (Thia)calix[4]-arenes with Terminal Double and Triple Bonds: Synthesis and Azide-Alkyne Click Reactions

“…Образу-ющееся с выходом 60 % соединение 8 было выделено в стереоизомерной форме частичный конус. Полученные результаты полностью согласуются с литературными, по которым каликс [4]арен с трет-бутильными заме-стителями в пара-положении при тетраалкилировании бромистым пропаргилом в присутствии карбоната цезия образует стереоизомер 1,3-альтернат [25] в качестве основного продукта, в то время как незамещенный по верхнему ободу каликс [4]арен образует смесь продуктов частичный конус:1,3-альтернат в соотношении 4:1. [18] Таким образом, при взаимодействии дистальных аллильных производных 4 и 5 с пропаргилбромидом в случае трет-бутильного каликс [4]арена 4 преобладает стереоизомер 1,3-альтернат, а в случае незамещенного по верхнему ободу соединения 5 -частичный конус, причем в последнем случае в реакционной смеси другие стереоизомеры обнаружены не были.…”