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Silylation of substituted benzhydroxamic acids: NMR spectra ( 13 C, 15 N and 29 Si) and structure of tert ‐butyldimethylsilyl derivatives
Author(s) -
Schraml Jan,
Kvičalová Magdalena,
Soukupová Ludmila,
Blechta Vratislav,
Exner Otto
Publication year - 1999
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/(sici)1099-1395(199909)12:9<668::aid-poc175>3.0.co;2-c
Subject(s) - substituent , chemistry , chemical shift , silylation , moiety , ring (chemistry) , carbon 13 nmr , benzene , nmr spectra database , chloride , stereochemistry , derivative (finance) , medicinal chemistry , computational chemistry , spectral line , catalysis , organic chemistry , physics , astronomy , financial economics , economics
Twelve para ‐ and meta ‐substituted benzhydroxamic acids were subjected to exhaustive silylation with N ‐( tert ‐butyldimethylsilyl)‐ N ‐methyltrifluoroacetamide (with 1% of tert ‐butyldimethylsilyl chloride as a catalyst). In all cases only one product was isolated. According to the assigned NMR spectra ( 13 C, 15 N, and 29 Si), the product is the Z ‐ O 1 , O 4 ‐bis( tert ‐butyldimethylsilyl) derivative of substituted benzhydroximic acid, independently of the nature of the para or meta substituent. For structure determination, the 29 Si shifts and 1 J ( 13 C, 13 CN) coupling constants are decisive. The chemical shifts ( 13 C, 15 N, 29 Si) show dependences on the substituent constants of various kinds: even the 13 C shift of the sixth atom from the benzene ring varies with substitution. The 13 C and 15 N chemical shifts of the CN moiety exhibit opposite dependences on the substituent; the 29 Si shifts of the two silicon atoms are almost equally sensitive to the substituent effects despite their different distances from the substituent. Copyright © 1999 John Wiley & Sons, Ltd.