Concave hydrocarbons, such as 1 (C36H36), 4 5 (C54H48), and 6 (C,,H 52), represent three-dimensionally clamped analogues of x-prismands. They encapsulate small metal ions and accomplish metal-ion extraction from aqueous solution. Their remarkable selectivity allows applications such as incorporation in ion-selective electrodes. The synthetic route is based on well-established cyclophane methodology and, thus, offers a general approach to a whole family of concave hydrocarbons.
The first catenanes containing sulfonamide units were synthesized. Selective formation of the i d o u t isomer 7 can b e explained by host-guest interactions that cause a regioselective templating effect. Replacement of 02S-NH by 02S-NMe increases the yield significantly (from 10 to 19%). The sulfonamide catenane 7 has a topologically chiral structure.Catenanes, intertwined polymembered rings, are fascinating because of the unusual way they are tied together, and they still are a preparative challenge to the synthetic organic chemist today. For a long period catenanes have only been accessible in low yields by statistic"] or multistep ['] syntheses. Presently, however, certain types of catenaned31 can be produced in preparative amounts by using supramolecular templating effectsI41.We focused on the mechanism of one of the most simple template-supported catenane syntheses and we were able to demonstrate that a key role is played by the macromonocycle (e.g. 6) that is also found as a side product of the reaction: A diacid dichloride (e.g. 5-methoxyisophthalic acid dichloride 5) or a corresponding monoamide acid chloride prepared from 4 and 5 can "nestle down" in the macromonocycle to then further react with ring Applying this procedure, we recently synthesized the first amidebased rotaxaneL61.In this paper we report the synthesis of topologically chiral catenanes of type 7 bearing sulfonamide units and further conclusions as to the mechanism of the intertwining process that can be drawn from their formation. C=O...H-N-hydrogen bonds have been shown to exist in catenaned71, and they are probably of importance in the templating effect, too. Thus, we were interested in examining whether the carbonamide units could be replaced by sulfonamide units. Since the steric, electronic, and hydrogen-bonding donorlacceptor properties of sulfonamides differ from those of carbonamides, such an exchange should effect molecular recognition and the templating effect. However, carrying out synthesis A under this aspect, we obtained neither catenanes nor monocycles but only openchain condensation products. Apparently, the formation of SO,-NHR bonds is sterically hindered in the macrocyclization step by the methyl substituents in ortho-position of diamine 1 a: In contrast, the corresponding conversion B with the non-substituted diamine l b at least gave the tetrasultam 3 in 13% yield. The latter, however, seems not to be a suitable template for the threading procedure in the next step, as no subsequent catenane formation occurs. We then decreased the number of sulfonamide groups, that seem to disturb the catenane formation, by reaction of the cyclization precursor 4, that only carries one sulfonamScheme 2. The reaction of cyclization precursor 4 with acid dichloride 5 leads to the formation of macromonocycle 6 and to the inlout catenane isomer (7)CH~CIZ. NEtj r.t. o=s=oHiv 4 HZ
The direct introduction of sulfonamide units (cf. 9) into CO-NH and then be substituted by treatment with suitable carboxamide-based rotaxanes allows us to intramolecularly iodo compounds. This leads intramolecularly to 11 (7 1 % bridge the "wheel" and the "axle" of such species for the yield) and intermolecularly to bis[2]rotaxane 16 (76% yield). first time as is shown by the bridged bissulfonamide rotaxane The iodo-substituted rotaxane 15 isolated as a remarkably 11. Due to its stronger acidity the S02-NH proton can be se-stable byproduct offers a new synthetic potential demonlectively abstracted by mild bases even in the presence of strated by the preparation of 16.While early statistical ['] and multistep[*] syntheses yielded rotaxanes"] only in analytical quantities, the application of supramolecular template effectd4] for several years allows their preparation on a laboratory However, the use of rotaxanes as structural entities for further reactions, in other words a preparative "chemistry with rotaxanes", has remained a dream so far.Directed incorporation of sulfonamide units['0] into the "wheel" and "axle" parts" of amide-based rotaxanes[12] as described below offers rather simple approaches to realize this goal: Due to their stronger acidity sulfonamide protons in such rotaxanes can be removed selectively by mild bases even in the presence of carboxylic acid amide protons. The sulfonamide units thus allow the selective alkylation by suitable iodo compounds in this position. Reaction with diiodo compounds results in intramolecular covalent bridging between "axle" and "wheel" sulfonamide groups and likewise intermolecular covalent connection leads to bis[2]rotaxanes[l31. Intramolecular Covalent LinkageInvestigating whether intramolecular covalent bridging in suitable rotaxanes was feasible, we first attempted to alkylate rotaxane 1 (prepared in 41 '% yield["]), which possesses a single sulfonamide unit in the "axle". Since the "wheel" could sterically hinder a substitution reaction on the "axle" site we chose the methyl group as a substituent of low steric demand. Therefore, an equimolar amount of K2C03 was DMF K2C0363 Yo
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