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Preparation and Mechanism of Solvolysis of N ‐Hydroxy‐ α ‐oxobenzeneethanimidoyl Chloride, a 2‐(Hydroxyimino)‐1‐phenylethan‐1‐one Derivative: Molecular Structure of α ‐Oxo‐oximes (= α ‐(Hydroxyimino) Ketones)
Author(s) -
Hameršak Zdenko,
Perić Berislav,
KojićProdić Biserka,
Cotarca Livius,
Delogu Pietro,
Šunjić Vitomir
Publication year - 1999
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/(sici)1522-2675(19990804)82:8<1289::aid-hlca1289>3.0.co;2-w
Subject(s) - chemistry , acetophenone , oxime , moiety , intramolecular force , stereochemistry , derivative (finance) , solvolysis , medicinal chemistry , chloride , intermolecular force , molecule , organic chemistry , catalysis , financial economics , hydrolysis , economics
Acid‐catalyzed methanolysis of N ‐hydroxy‐ α ‐oxobenzeneethanimidoyl chloride ( 1 ), a 2‐(hydroxyimino)‐1‐phenylethan‐1‐one derivative obtained in one step from acetophenone, leads to a constant ratio of methyl α ‐oxobenzeneacetate ( 2 ) and methyl α ‐(hydroxyimino)benzeneacetate ( 3 ). 13 C( α ) Labelled [ 13 C]‐ 1 affords 13 C( α ) labelled [ 13 C]‐ 3 , thus discarding the hypothesis of its formation via 1,2‐arene migration. The reported sequence opens a novel approach to phenylglyoxylic and mandelic acid esters (= α ‐oxobenzeneacetic and α ‐hydroxybenzeneacetic acid esters), from acetophenone. The molecular structures of 1 and 3 were determined by X‐ray structure analysis and compared with previously reported crystallographic data of α ‐oxo‐oximes (= α ‐(hydroxyimino) ketones) 4 and 6 – 8 . The unique stereoelectronic characteristics of the α ‐oxo‐oxime moiety are discussed. All α ‐oxo‐oximes share the following structural characteristics: ( E )‐configuration of the oxime C=N−OH bond ( i.e. OH and C=O trans ), the s‐ trans conformation of the oxo and imino moieties about the C( α )‐C(=NOH) single bond, and inter molecular H‐bonding. They differ from the isostructural β ‐diketone enols by the absence of resonance‐assisted intra molecular H‐bonding.