Template synthesis of the first amide‐based rotaxanes

Abstract

The first rotaxanes 6a, 6b and 11 with a n amide structure are described. Their (supramolecular template) syntheses are strikingly simple. The central part of the "axle" is added to the "wheel" and subsequently capped. The macromonocycle ("wheel") provides the receptor cavity for the "axle" and the triphenylmethane stoppers confirm the mechanical bond between "wheel" and "axle".While in the synthesis of the first rotaxanes Schill et al. connected "wheel" and "axle" through covalent bonds to form prerotaxanes['l, mechanical bonds have recently been tied more easily by the use of supramolecular template effectsl21. Particularly, complexing metal and donoracceptor interaction~ [~] have been employed successfully also with cyclodextrin building elementsL5]. A mechanism recently suggested by us [6] for the template-directed formation of carboxylic amide catenanesL7I may also be used for the preparation of rotaxanesL'1. We could show that in the formation of the catenane, a macromonocycle of the type 3 is generated initially. The isophthaloylic moiety like 1, which according to molecular models shows a good fit, is incorporated as host almost orthogonally before reacting with a diamine 2 to form the second catenane ring. We assume that the incorporation of 1 in 3 is due to several effects: steric fit, n-.n interactions, and NH...O=C hydrogen bonds between host and guestL61. On this basis, we herein describe the synthesis of rotaxanes with an amide structure.In conformity with the synthesis of catenanes, we first charged the host, i.e. the macromonocycle 3a (or 3b), into the cavity of which the dicarboxylic acid dichloride l a (or a corresponding monochloride monoamide 7) can be nested. The resulting supramolecular intermediate 4a (or 4b) should then be treated with bulky stoppers to form the desired rotaxane 6a (or 6b).The stopper component 5 must be selected such that the rotaxane "axle" is of a certain minimum length to prevent steric hindrance of the reaction [']. Initially, we employed as stopper reagent the diamine 8 which has proven successful in the synthesis of the corresponding catenanes. In order to reduce the competing formation of a catenane, it was added in a large excess to a 1 : 1 mixture of l a and 3a. The formation of a rotaxane, however, could not be detected. For this reason, we then replaced the diamine 8 by the monofunctionalized (4-aminopheny1)triphenylmethane (Ctritylaniline) (5) which prevents the competing reaction to afford the catenane due to the absence of a second amino group.

Template synthesis of rotaxanes with carbamate-linked axles

“…The preparation of this new macrocycle 9 was carried out according to macrocycles 1 [8] and 2 [9]. Reaction of 2,6-pyridine dicarboxylic acid dichloride 22 with diamine 23 [13] led to diamide 24 [14] in 34% yield.…”

“…In 1997 we were able to introduce diisocyanates [7] as building blocks. Treatment of macrocycles 1 [8] and 2 [9] with diisocyanates 3 and 4 and further reaction with bulky amine stoppers 5 led to rotaxanes 6 -8 with urea-linked axles [10] in 4 -11% yield (Scheme 1). First attempts to synthesize these rotaxanes at room temperature failed, so we raised the reaction temperature to 40 °C.…”

Calixarenes as Stoppers in Rotaxanes

“…Yield 0.874 g (87%). Ϫ R f ϭ 0.31 (2, 24 H, ar-127.8, 128.3, 128.4 (m-ar), 134.7, 135.6 (o-ar, p-ar) 6,123.9,124.3,125.2,126.1,, Dumbbell 4a: The reaction was carried out using 178 mg (0.2 130.8, 132.3, 134.4, 135.0, 136.1, 141.1, 143.4, 144.7, 149.3, 152.9, mmol) 16 H,17,26,27,calix [4] (2,6.83 (t,4 H,J ϭ 7.4 Hz),6.96 (d,4 H,J ϭ 7.2 Hz),6.97 (d,4 H,J ϭ 7.2),7.71 (s,8 H, 2, 122.0 (p-ar), 127.0, 127.2, 127.5, 127.6, 128.5, 128.7 (m-ar 130.6, 134.1, 134.2, 134.5, 136.2, 136.3, 143.1 (C q ), 155.5, 156.0, 157.3 (ipso-ar) 2 H,J ϭ 11,17, 6 amino-25,26,27,28-tetrakis(1-pentyloxy)calix [4]arene (16a): To a MHz, CDCl 3 , 25°C): δ ϭ 14.0, 14.1, 14.4 (CH 3 ), 22.8, 23.0 solution of 0.9 g (1 mmol) of compound 3a, some drops NEt 3 and (CH 2 CH 3 ), 28. 2, 28.6, 28.7, 29.8, 30.2, 31.0, 31.2, 31.3, 31.6, 31 1,124.4,125.4,126.0,, 131.4, chloride in 25 ml of dry CH 2 Cl 2 at room temp.…”

“…The minimum length of the accessible in preparative yields, too. We applied a non-ionic thread between the stopper units, that was necessary to pretemplate synthesis [6] to get amide-based rotaxanes with up vent steric hindrance during the rotaxane formation, was to 48% yield [7] . Beside our interest in preparing covalently intended to be determined by variation of the spacer belinked rotaxanes [7] [8b] [9] we aim at testing the flexibility of tween the calixarene ring and the amino group needed for the template synthesis through structural modification.…”

Tetralactam-modified gold electrodes for amperometric detection of acrylic acid

“…Hydrogen bonds formation and π-π interaction were responsible for the formation of catenate and rotaxanes. Their synthesis was based on the action of supramolecular nucleophile that is formed from the molecular recognition of an anionic stopper by a tetralactam wheel [23][24][25].…”