CONFORMATIONAL-ANALYSIS OF 2,3-DISUBSITITUED 1,4-DITHIANES BY NMR-SPECTROSCOPY AND MMX CALCULATIONSстатья
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:The conformer populations for trans- and cis-2,3-disubstituted 1,4-dithianes have been determined by H-1 and C-13 NMR spectroscopy and calculated by molecular mechanis (MMX). The CH(2)X-substituents demonstrate the strong preference for axial position. The remarkable difference originating from intramolecular steric interactions has been observed between tow trans-dialkyl derivatives: the trans-2,3-dimethyl-1,4-dithiane is predominantly equatorial whereas trans-2,3-dipropyl-1,4-dithiane prefers diaxial conformation. The properties of cis-2,3-dipropyl-1,4-dithiane are also unusual: its ring interconversion is unexpectedly slow (Delta G(not equal) = 11.2 kcal mol(-1) at 260K).