Synthesis of Enantiopure C₃‐Symmetric Triangular Molecules

Abstract

An asymmetric synthesis of C 3 -symmetric triangular macrocycles is reported. 1-Methylsulfonyl-4-(4-vinylphenyl)-1,2,3-triazole undergoes ar hodium(II)-catalyzed cyclotrimerization to establish an enantiopure C 3 -symmetric triangular macrocycle motif.This method can be applied to the synthesis of an enantiopure hydrocarbon, which owes its chirality to asymmetric distribution of H/D atoms on the benzene rings. Scheme 1. a) Asymmetric synthesis of chiral cyclopropanes using triazole. b) Design and synthesis of triazole 1. Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: http://dx.doi.org/10.1002/anie.201612585. Angewandte Chemie Communications Scheme 3. The reaction of 1 at low concentrations.Scheme 4. a-Diazo imine generated from 1a nd a-diazo ester 6. Angewandte Chemie Communications 3335

Chiral Macrocycles Having C3 Symmetry Resulting from Orientation of Thiophene Rings

“…These chiral structures of the C 3 ‐symmetric macrocycles 9 and 10 are unique since their chiralities are ascribed solely to the orientation of the unsymmetrical 2,4‐disubstituted thiophene rings. We previously reported the synthesis of the achiral macrocycle, that is, cyclic [3]paraphenylenecyclopropylene ([3]CPPC) which had C 3 v symmetry [8a] . In the present study, the 1,4‐phenylene linkers are replaced by the unsymmetrical 2,4‐thienylene linkers, which are directionally oriented.…”

“…[14] The resulting crude reaction mixture was analyzed by highresolution mass spectrometry to observe the formation of various cyclic products ranging from a dimer to a pentamer in addition to small amounts of linear products. Although cyclic trimers were most dominant, the product distribution was broader than that of the reaction of 1-(N-mesyltriazolyl)-4vinylbenzene, [8] probably because of the deviation of the angle of 2,4-disubstitution of thiophene (ca. 1328) from 1808.…”

“…[6,7] With this excellent synthetic tool available, we designed a new bifunctional monomer, which possesses triazolyl and vinyl groups at para positions on a benzene core for a head-to-tail type oligomerization. [8] Its reaction catalyzed by a chiral Rh II complex favored cyclotrimerization forming enantioenriched triangular macrocycles, in which three benzene rings and three cyclopropane rings of same absolute configuration were alternately arranged. As a result, the triangular macrocycles have threefold rotational symmetry.…”