A Tandem Reaction Initiated by 1,4-Addition of Bis(iodozincio)methane for 1,3-Diketone Formation

Electrochemical Radical Reaction Construction of C-C Bonds: Access to 1,4-Dicarbonyl Compounds from Enol Acetates and 1,3-Diketones

As important substrates for the construction of heterocycles, a simple and efficient approach for synthesis of 1,4-diones is highly desirable. In this work, novel and efficient electrochemical radical reactions of enol acetates and 1,3-diketones have been developed to successfully achieve 1,4-diketones under catalyst-free and oxidant-free conditions. The wide range of substrates, good group tolerance, and simple operation process make the approach have important practical value. Moreover, the obtained 1,4-diketones can be easily further transformed to pyrrole and furan derivatives.

Recent Developments in the Synthesis of β-Diketones

Apart from being one of the most important intermediates in chemical synthesis, broadly used in the formation of C-C bonds among other processes, the β-dicarbonyl structure is present in a huge number of biologically and pharmaceutically active compounds. In fact, mainly derived from the well-known antioxidant capability associated with the corresponding enol tautomer, β-diketones are valuable compounds in the treatment of many pathological disorders, such as cardiovascular and liver diseases, hypertension, obesity, diabetes, neurological disorders, inflammation, skin diseases, fibrosis, or arthritis; therefore, the synthesis of these structures is an area of overwhelming interest for organic chemists. This paper is devoted to the advances achieved in the last ten years for the preparation of 1,3-diketones, using different chemical (Claisen, hydration of alkynones, decarboxylative coupling) or catalytic (biocatalysis, organocatalytic, metal-based catalysis) methodologies: Additionally, the preparation of branched β-dicarbonyl compounds by means of α-functionalization of non-substituted 1,3-diketones are also discussed.

Synthesis of Highly Substituted Biaryls by the Construction of a Benzene Ring via In Situ Formed Acetals

Herein, we present an interesting method for the construction of a benzene ring using propargylic alcohols and 1,3-dicarbonyls, which involves three new C-C bond formations via cascade alkylation, formylation, annulation, and aromatization to make substituted biaryls. This one-pot Brønsted acid-promoted protocol utilizes the unique reactivity of the acetal formed under the reaction conditions. Alkynyl methyl ketones could be employed instead of 1,3-dicarbonyls as they are converted to 1,3-dicarbonyls by hydration under the reaction conditions.

Chromophores inspired by the colors of fruit, flowers and wine

Anthocyanins, which are responsible for most of the red, blue and purple colors of fruits and flowers, are very efficient at absorbing and dissipating light energy via excited state proton transfer or charge-transfer mediated internal conversion without appreciable excited triplet state formation. During the maturation of red wines, grape anthocyanins are slowly transformed into pyranoanthocyanins, which have a much more chemically stable pyranoflavylium cation chromophore. Development of straightforward synthetic routes to mono- and disubstituted derivatives of the pyranoflavylium cation chromophore has stimulated theoretical and experimental studies that highlight the interesting absorption and emission properties and redox properties of pyranoflavylium cations. Thus, p-methoxyphenyl substitution enhances the fluorescence quantum yield, while a p-dimethylaminophenyl substituent results in fast decay via a twisted intramolecular charge-transfer (TICT) state. Unlike anthocyanins and their synthetic analogs (flavylium cations), a variety of pyranoflavylium cations form readily detectable excited triplet states that sensitize singlet oxygen formation in solution and exhibit appreciable two-photon absorption cross sections for near-infrared light, suggesting a potential for applications in photodynamic therapy. These excited triplet states have microsecond lifetimes in solution and excited state reduction potentials of at least 1.3 V vs. SCE, features that are clearly desirable in a triplet photoredox catalyst.

An effective preparation of both 1,3-diketones and nitriles from alkynones with oximes as hydroxide sources

An effective phosphine-catalyzed protocol has been established for the syntheses of 1,3-diketones and nitriles from alkynones with oximes as hydroxide surrogates. This method features the use of a phosphine catalyst, compatibility with various functional groups and ambient temperature, which makes this approach very practical. A plausible mechanism was proposed.

Facile access to 1,3-diketones by gold(i)-catalyzed regioselective hydration of ynones

A regioselective hydration of ynones was developed via gold catalysis, providing a simple, mild, and efficient method for the synthesis of a variety of 1,3-diketone derivatives.

Enantioselective synthesis of chiral acylsilanes by copper/HZNU-Phos-catalyzed asymmetric conjugate addition of diethyzinc to α,β-unsaturated acylsilanes

The catalytic asymmetric copper-catalyzed conjugate addition of diethylzinc reagent to α,β-unsaturated acylsilanes was found to proceed smoothly in moderate to good yields and enantioselectivities (up to 85% ee) in the presence of the multifunctional HZNU-Phos.

Advances in tandem reactions with organozinc reagents

A review of recent advances in tandem reactions with organozinc reagents that highlight their utility in organic synthesis.

Preparation of cycloheptane ring by nucleophilic cyclopropanation of 1,2-diketones with bis(iodozincio)methane

The nucleophlic cyclopropanation of hexa-1,5-diene-3,4-diones with bis(iodozincio)methane afforded the Zn alkoxides of cyclohepta-2,7-diene-1,2-diols stereospecifically via Zn alkoxides of cis-dialkenylcyclopropane-1,2-diols.

Diasteroselective preparation of cyclopropanols using methylene bis(iodozinc)

A diastereoselective synthesis of trans-2-substituted cyclopropanols is outlined. Bimetallic CH(2)(ZnI)(2) was found to react with α-chloroaldehydes to give cyclopropanols in yields of 64-89% and dr's ≥ 10:1. The high trans-selectivity resulted from equilibration of the cyclopropoxide intermediates.