Electrophilicity of 5-Benzylidene-1,3-dimethylbarbituric and -thiobarbituric Acids
摘要:
[Graphics]The kinetics of reactions of acceptor-stabilized carbanions 2a-m with benzylidenebarbituric and -thiobarbituric acids 1a-e has been determined in a dimethyl sulfoxide solution at 20 degrees C. Second-order rate constants were employed to determine the electrophilicity parameters E of the benzylidenebarbituric and -thiobarbituric acids la-a according to the correlation equation log k(20 degrees C) = s(N + E). With E parameters in the range of -10.4 to -13.9, the electrophilicities of la-a are comparable to those of analogously substituted benzylidenemalononitriles.
Synthesis of novel 5-monoalkylbarbiturate derivatives: new access to 1,2-oxazepines
作者:Assem Barakat、Mohammad Shahidul Islam、Abdullah M. Al-Majid、Saied M. Soliman、Yahia N. Mabkhot、Zeid Abdullah Al-Othman、Hazem A. Ghabbour、Hoong-Kun Fun
DOI:10.1016/j.tetlet.2015.10.108
日期:2015.12
A simple and straightforward route to 5-monoalkylbarbiturates by the NHEt2 catalyzed Michael reaction of 1,3-dimethylbarbituric acid and alpha,beta-unsaturated ketones is described. Significantly, the reaction exclusively furnished 5-monoalkylbarbiturates. Under neat conditions, the mixing and grinding of a representative 1,5-diketone and hydroxylamine hydrochloride gave the corresponding 1,2-oxazepine in very good yield. (C) 2015 Elsevier Ltd. All rights reserved.