Please use this identifier to cite or link to this item: http://scholarbank.nus.edu.sg/handle/10635/95121
Title: Synthesis of dithia[3.3]biphenyleno(2,2′)(1,2)-, (1,3)-, (1,4)cyclophanes and their atropisomerism and dynamic stereochemistry
Authors: Lai, Y.-H. 
Wong, S.-Y. 
Hsieh-Yao Chang, D.
Issue Date: 15-Jan-1993
Source: Lai, Y.-H.,Wong, S.-Y.,Hsieh-Yao Chang, D. (1993-01-15). Synthesis of dithia[3.3]biphenyleno(2,2′)(1,2)-, (1,3)-, (1,4)cyclophanes and their atropisomerism and dynamic stereochemistry. Tetrahedron 49 (3) : 669-676. ScholarBank@NUS Repository.
Abstract: The dithiacyclophanes (1), (2), (3) and (4) were prepared by intermolecular cyclization reactions under high dilution conditions. Detailed 1H NMR spectroscopic analyses and dynamic NMR studies have indicated that pseudo-rotation of the biphenyl unit is restricted up to a temperature of 443K in (1), (2) and (3) involving energy barriers estimated to be > 75 kJ mol-1. At room temperature, a flipping process of the 1,3-bridged ring in (1) and (2) is however clearly evident based on analyses of the aromatic protons in the 1D and 2D 1H NMR spectra. The dithiacyclophane (4) proves to be conformationally the most mobile among the three members and exhibits two-step conformational processes involving first an inversion process of the 1,2-bridged ring followed by a pseudo-rotation (racemization) of the biphenyl moiety, with an estimated free energy of activation of 61.9 kJ mol-1, at high temperatures. © 1993.
Source Title: Tetrahedron
URI: http://scholarbank.nus.edu.sg/handle/10635/95121
ISSN: 00404020
Appears in Collections:Staff Publications

Show full item record
Files in This Item:
There are no files associated with this item.

Page view(s)

39
checked on Feb 16, 2018

Google ScholarTM

Check


Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.