The Effect of Ring Size on Catenane Synthesis

Abstract

The synthesis of a [2]catenane with 87‐membered rings was improved and extended to [2]catenanes with 63‐ and 147‐membered rings. One of the key features is the carbonate linkage between phenols with tolane substituents in the 2‐ and 6‐positions, which serves as a covalent template for the geometrical arrangement of a macrocycle and a ring precursor. Subsequent cyclization of the threaded ring precursor gives the precatenane as the main product, and this is converted into the catenane by carbonate hydrolysis. As well as the precatenane, its dumbbell shaped isomer is formed in the cyclization step. From the known conformation of the templating carbonate moiety and the strong dependence of the ratio of precatenane and dumbbell on the ring size, the dumbbell's origin is attributed to the conformational flexibility of the large rings and not to geometrical ambiguity of the carbonate moiety. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Co‐Conformational Distribution of Nanosized [2]Catenanes Determined by Pulse EPR Measurements

“…The systems studied here are [2]catenanes2 with the intention to learn about their co‐conformation,3 which is the relative orientation of the two rings. In contrast to the case with other catenanes,4 with the catenanes 1 – 3 ,2a,2b NMR spectroscopy fails to reveal the co‐conformation as well as changes in the co‐conformation. The rings are very large and are devoid of functional groups that would lead to distinct ring–ring interaction.…”

Data analysis procedures for pulse ELDOR measurements of broad distance distributions

“…Synthesis of the shape-persistent biradical [25] and of the doubly spin-labelled [2]catenane [6,26] have been desc¡ earlier. The double mutant S106C/Sl£ of the LHCII apoprotein was dissolved (1 mg/ml) in ah aqueous solution of sodium dodecyl sulfate (0.5 weight%) and sodium phosphate buffer of pH 7 (20 mM).…”

Non‐Rusty [2]Catenanes with Huge Rings and Their Polymers

“…Freely rotating rings and a sufficient degree of freedom for lateral displacement were the leading aspects when designing the catenanes 18. [24] Moreover, the 1 H NMR spectroscopic data of the catenanes s-18a, m-18a, and l-18a, which vary in ring size, differ by 0.03 ppm at most. Because of the huge ring sizes and the lack of strongly interacting functional groups, we expected the two rings to have a random orientation relative to one another; in other words, we expected the catenanes to adopt all possible coconformations [2] in equal abundances.…”

“…[57] Altogether, transferring the reaction conditions that we had elaborated using the model compounds went smoothly and the catenanes 18 were obtained as depicted in Scheme 5 through route A comprising the following steps: [24] (1) cyclisation of Scheme 5. a) NaH, THF; b) CuCl, CuCl 2 , pyridine, pseudo-high dilution; c) Cl 2 CO, iPr 2 NEt, THF or CH 2 Cl 2 ; d) for 15a: ϩ 12a(Na), THF; for 15b: ϩ 12b(H), DMAP, THF; for 15c: ϩ 12c(H), DMAP, THF; e) for hydrolysis of 16a, 17a, and 21a: nBu 4 NF, THF, 50°C; for hydrolysis of 16b,c and 17b,c: 10  NaOH, THF, EtOH, 50°C; f) (Cl 3 CO) 2 ring precursors 12a(H) to obtain macrocycles 13a by employing the oxidative dimerization of alkynes under conditions of pseudo-high dilution by slow addition of 12a(H) to a suspension of CuCl and CuCl 2 in pyridine, (2) conversion of macrocycles 13a into the corresponding chloroformates 14a through reaction with phosgene in the presence of iPr 2 NEt, (3) threading of these macrocycles onto 12a(Na), the sodium salts of the ring precursors, with the formation of the carbonates 15a, (4) cyclisation by oxidative dimerization of the alkynes as in the first step to give the precatenanes 16a, and finally (5) carbonate cleavage with nBu 4 NF in THF to obtain the catenanes 18a. Although in a multistep synthesis, the ring precursors can be prepared on multigram scales Scheme 4. a) CuCl, CuCl 2 , pyridine, pseudo-high dilution (4Ϫ10 g) by a partially convergent route.…”

“…This approach uses the complexation of Cu I by phenanthroline to organise the two building blocks -either two ring precursors or one ring and one ring precursor -geometrically in such a way that after the cyclisation step the two rings are intertwined. [24] Using a covalent bond to arrange the building blocks during a catenane synthesis may appear to be a step backwards in development. Scheme 1 Inspired by this work, we developed a strategy based on a carbonate linkage between appropriately substituted phenols as the templating unit.…”