10.1002/(SICI)1099-0690(199912)1999:12<3343::AID-EJOC3343>3.0.CO;2-S
The research explores the synthesis and reactivity of tetraacylethenes, specifically tetraacetylethylene (7a) and diacetyldibenzoylethylene (7b), in Diels–Alder reactions. The study aims to provide a novel access to functionalized [4.3.3]propellanes and clarify conflicting reports on the oxidative coupling of benzoylacetone (15b). The researchers found that tetraacetylethylene (7a) behaves as a mechanistic chameleon, yielding two different Diels–Alder products with 1,2-dimethylenecyclohexane, and can react as both an electron-deficient dienophile and a 1-oxa-1,3-diene. Key chemicals used in the process include barium manganate, iodosobenzene, 1,2-dimethylenecyclohexane, and various derivatives of benzoylacetone. The conclusions drawn from the study are that tetraacetylethylene (7a) is a versatile reactant in Diels–Alder reactions, capable of forming different products depending on the reaction conditions, and that the reactions likely proceed via a zwitterionic intermediate, offering insights into the ambiguity observed in the Diels–Alder chemistry of such compounds.
10.1002/ejoc.200701140
The study presents the first synthesis and characterization of open-chain cyclopropylpolyketides through a combination of experimental and computational methods. Researchers synthesized cyclopropylpolyketides by a sequence of chain elongation via acylation and subsequent cyclopropanation. Key chemicals involved include 1(cyclopropyl)butane-1,3-dione and benzoylacetone, which were used as starting materials for cyclopropanation with 1,2-dibromoethane to form cyclopropanes 2a and 2b. These cyclopropanes were then reacted with cyclopropanecarboxylic chloride and benzoyl chloride to produce compounds 3a–c, which were further cyclopropanated to yield the desired cyclopropyltriketides 4a–c. The structure of 4c was confirmed by X-ray crystal structure analysis. Additionally, dimethyl cyclopropane-1,1-dicarboxylate (5) was reacted with 1-cyclopropylethan-1-one to form 7, which was transformed into triketide 8. The study also involved density functional theory computations to analyze the structural and energetic properties of the cyclopropylpolyketides, providing insights into their conformations and stabilities.
10.1080/00397910802439209
Peiju Yang et al. reports the isolation and characterization of three half-condensed pyrazoline intermediates (2b–2d) during the synthesis of N-(1,10-phenanthroline)-pyrazole derivatives via the Knorr reaction. The study details the synthesis of these intermediates from benzoylacetone and 2-hydrazine-1,10-phenanthroline derivatives, highlighting the importance of controlling reaction time to prevent their conversion to pyrazoles. The intermediates were characterized using NMR spectroscopy and X-ray diffraction, revealing intramolecular hydrogen bonds and the influence of steric hindrance on their stability and dehydration to form pyrazoles. The findings provide insights into the mechanism of the Knorr reaction and the role of substituents in determining the stability and reactivity of pyrazoline intermediates.
