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A Self‐Threaded “Molecular 8”
Author(s) -
Reuter Carin,
Wienand Wolfgang,
Schmuck Carsten,
Vögtle Fritz
Publication year - 2001
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20010417)7:8<1728::aid-chem17280>3.0.co;2-z
Subject(s) - rotaxane , racemization , axle , enantiomer , chemistry , molecule , yield (engineering) , chirality (physics) , stereochemistry , crystallography , supramolecular chemistry , materials science , organic chemistry , nambu–jona lasinio model , chiral symmetry breaking , physics , quantum mechanics , mechanical engineering , engineering , metallurgy , quark
A new type of [1]rotaxanes containing two aliphatic bridges between axle and wheel is obtained in 39 % yield in a one‐step synthesis starting from a [2]rotaxane which contained one sulfonamide group each in both the wheel and the axle. Temperature controlled chemoselective substitution reactions first at these sulfonamide nitrogens and then subsequently at the various other carboxamide nitrogens in the wheel and axle give rise to the formation of an isomeric mixture of three double‐bridged [1]rotaxanes which could be separated by HPLC. Structure determination of the main product 3 a was possible by NMR experiments supported by molecular modeling calculations. Using different reaction conditions, a double‐substituted but not yet bridged [2]rotaxane 4 could be isolated as an intermediate giving further evidence for the assigned structure of 3 a and the way of its formation. The shape of this double‐bridged [1]rotaxane 3 a reminds of a self‐intertwining chiral “molecular 8”, in which any possible racemization due to deslipping is hindered by the two stoppers originating from the former rotaxane axle. Hence, to the best of our knowledge this is the first example of a molecule in which both concepts, cycloenantiomerism and helical chirality, are realised in one structure. Enantiomer separation of the main product was possible by further HPLC using chiral stationary phases. The Cotton effects of the circular dichrograms are different to those of the already synthesized [1]rotaxanes bearing just one aliphatic bridge between axle and wheel.