75863-79-5Relevant articles and documents
Single-Step Enantioselective Synthesis of Mechanically Planar Chiral [2]Rotaxanes Using a Chiral Leaving Group Strategy
Tian, Chong,Fielden, Stephen D.P.,Pérez-Saavedra, Borja,Vitorica-Yrezabal, I?igo J.,Leigh, David A.
, p. 9803 - 9808 (2020/06/17)
We report a one-step enantioselective synthesis of mechanically planar chiral [2]rotaxanes. Previous studies of such molecules have generally involved the separation of enantiomers from racemic mixtures or the preparation and separation of diastereomeric intermediates followed by post-assembly modification to remove other sources of chirality. Here, we demonstrate a simple asymmetric metal-free active template rotaxane synthesis using a primary amine, an activated ester with a chiral leaving group, and an achiral crown ether lacking rotational symmetry. Mechanically planar chiral rotaxanes are obtained directly in up to 50% enantiomeric excess. The rotaxanes were characterized by NMR spectroscopy, high-resolution mass spectrometry, chiral HPLC, single crystal X-ray diffraction, and circular dichroism. Either rotaxane enantiomer could be prepared selectively by incorporating pseudoenantiomeric cinchona alkaloids into the chiral leaving group.
Solid-State Inclusion Compounds of New Host Macrocycles with Uncharged Organic Molecules. Host Synthesis, Inclusion Properties, and X-ray Crystal Structure of an Inclusion Compound with 1-Propanol
Weber, Edwin,Josel, Hans-Peter,Puff, Heinrich,Franken, Sybille
, p. 3125 - 3132 (2007/10/02)
A series of organic macrocycles composed of a systematically varied combination of ethano, propano, benzeno, pyridino,and analogous groups, mainly ether-linked (see Chart I), are reported, and their abilities to function as solid-state inclusion hosts are studied.It is found that 3-5, 11-13, 18b, and 21 form crystalline inclusion compounds with a number of low-molecular-weight alcohols such as methanol, ethanol, 1- and 2-propanol, 1-butanol, ethylene glycol, and/or with dimethylformamide and acetonitrile as CH-acidic guests.The observed inclusion selectivities and thestoichiometries of the various host-guest compounds are discussed showing that by and large both chemical and steric host-guest fits apply in the formation of the aggregates.The crystal structure of the inclusion compound of the bipyridino host 11 with 1-propanol (1:1) has been determined from single-crystal X-ray diffraction.There are eight host and guest molecules in each unit cell of dimension a = 2665.2 pm, b = 813.8 pm, c = 2667.4 pm, β = 105.61 deg; space group C2/c; R = 0.088 for 2884 unique reflections.The host macrocycle shows a hollow-type conformation with the 1-propanol molecule coordinated via a moderately stable H-bond to one of the bipyridine nitrogens (O...N = 300 pm).The packing diagram characterizes the host-guest topology largely as a channel-like clathrate (actually "tubulato-coordinatoclathrate").A number of general conclusions that will facilitate the future design of selectively binding hosts for solid-state inclusion are given.
