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Derivatives of hydroxamic acids
Author(s) -
Schraml Jan
Publication year - 2000
Publication title -
applied organometallic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.53
H-Index - 71
eISSN - 1099-0739
pISSN - 0268-2605
DOI - 10.1002/1099-0739(200010)14:10<604::aid-aoc45>3.0.co;2-3
Subject(s) - chemistry , substituent , chemical shift , ring (chemistry) , hydroxamic acid , tautomer , oxalic acid , methylene , medicinal chemistry , yield (engineering) , stereochemistry , organic chemistry , materials science , metallurgy
Despite the biological importance and rich chemistry of hydroxamic acids (HAs), their organometallic derivatives have received little attention so far. Fully silylated (trimethylsilyl and t‐butyldimethylsilyl) derivatives which are promising for medicinal applications have a structure derived from that of the tautomeric hydroximic acid with an E/Z ratio depending on the nature of the acid. Aliphatic acids yield disilyl derivatives in an approximate E/Z ratio of 2:3; aromatic HAs produce solely Z isomer irrespective of the phenyl ring substituent. Silylation of aliphatic dihydroxamic acids proceeds independently on both ends if the two hydroxamic groups are separated by one methylene group at least. It was not possible to determine the E/Z ratio for oxalic and malonic acid derivatives. It is shown that 29 Si and 15 N NMR chemical shifts are useful for differentiation between hydroxamic and hydroximic structures, but for determination of E and Z configurations spin–spin coupling must be used until more data relating 29 Si, 13 C and 15 N chemical shifts to the configuration are available for this class of compounds. The dependence of chemical shifts on Hammett substituent constants in ring‐substituted benzhydroxamic acids is discussed. Some errors found in the literature on hydroxamic acids are also explained. Copyright © 2000 John Wiley & Sons, Ltd.