Universität zu Köln

Schade, Alexander ORCID: 0000-0002-6826-0656, Tchemook, Ivan, Bauer, Mirko, Oehlke, Alexander, Breugst, Martin ORCID: 0000-0003-0950-8858, Friedrich, Joachim and Spange, Stefan (2017). Kinetics of Electrophilic Alkylations of Barbiturate and Thiobarbiturate Anions. J. Org. Chem., 82 (16). S. 8476 - 8489. WASHINGTON: AMER CHEMICAL SOC. ISSN 1520-6904

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Abstract

Second-order rate constants (k(2)) of the reactions of various barbiturate anions such as the parent barbiturate, 1,3-dimethylbarbiturate, 2-thiobarbiturate, and 1,3-diethyl-2-thiobarbiturate with diarylcarbenium ions and Michael acceptors have been determined in dirnethyl sulfoxide solution at 20 degrees C. The reactivity parameters N and s(N) of the barbiturate anions were derived from the linear plots of log k(2) versus the electrophilicity parameters E of these reference electrophiles, according to the linear-free-energy relationship log k(2) (20 degrees C) = s(N) (E + N). Several reactions of these nucleophiles with benzylidenemalononitriles and quinone methides proceeded with reversible formation of the new C-C-bond followed by rate-determining proton shift. No evidence for initial attack of the electrophiles at the enolate oxygens of these nucleophiles was found by the kinetic measurements, in line with quantum chemical DFT calculations, which showed that in all cases C-attack is kinetically and thermodynamically preferred over O-attack. The nucleophilic reactivities of barbiturate anions were compared with those of structurally related carbanions, e.g., Meldrum's acid and dimedone anions.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Schade, Alexander UNSPECIFIED orcid.org/0000-0002-6826-0656 UNSPECIFIED Tchemook, Ivan UNSPECIFIED UNSPECIFIED UNSPECIFIED Bauer, Mirko UNSPECIFIED UNSPECIFIED UNSPECIFIED Oehlke, Alexander UNSPECIFIED UNSPECIFIED UNSPECIFIED Breugst, Martin UNSPECIFIED orcid.org/0000-0003-0950-8858 UNSPECIFIED Friedrich, Joachim UNSPECIFIED UNSPECIFIED UNSPECIFIED Spange, Stefan UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-221662
DOI:	10.1021/acs.joc.7b01223
Journal or Publication Title:	J. Org. Chem.
Volume:	82
Number:	16
Page Range:	S. 8476 - 8489
Date:	2017
Publisher:	AMER CHEMICAL SOC
Place of Publication:	WASHINGTON
ISSN:	1520-6904
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Chemistry > Institute of Organic Chemistry
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language ZETA-VALENCE QUALITY; GAUSSIAN-BASIS SETS; NUCLEOPHILIC REACTIVITIES; ENOLIZABLE BARBITURATE; AMBIDENT REACTIVITIES; UNIQUE BEHAVIOR; MELDRUMS ACID; PARAMETERS; ACCURATE; QUANTIFICATION Multiple languages Chemistry, Organic Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/22166