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α,β-Unsaturated acetylenic γ-hydroxyketones have been shown to react with ethyl acetoacetate in a Michael-addition fashion and subsequently undergo cyclization followed by dehydration to give substituted furans with a predictable regiospecificity. The yields were good to excellent. A mechanism for the transformation is proposed, and this mechanism explains why furan formation does not take place when the same unsaturated ketones are treated with α-methylated acetoacetate and diethyl malonate. [Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource: Full experimental and spectral details.] 相似文献
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Catalyzed by samarium triiodide (SmI3), substitution of acyl with N‐acylbenzotriazoles for acetyl in acetoacetic esters and acetylacetone proceeds smoothly under neutral conditions in open air, affording the corresponding β‐keto esters and β‐diketones in good yields. 相似文献
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α,β-Alkynyl ketoesters were introduced to the enantioselective Henry reaction (nitroaldol condensation) with nitromethane catalyzed by tartaric acid derived chiral iminophosphoranes. As such, a variety of optically active β-nitro-substituted tertiary alcohols bearing alkyne moieties were obtained in good to excellent yields (42%-99%) and moderate to good level of enantiomeric excess (up to 87% ee). 相似文献
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Insertion of Isolated Alkynes into Carbon–Carbon σ‐Bonds of Unstrained Cyclic β‐Ketoesters via Transition‐Metal‐Free Tandem Reactions: Synthesis of Medium‐Sized Ring Compounds 下载免费PDF全文
Yuanyuan Zhou Xianghua Tao Qiyi Yao Yulei Zhao Prof. Dr. Yanzhong Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(50):17936-17939
The transition‐metal‐free insertion of isolated alkynes into carbon–carbon σ‐bonds of unstrained cyclic β‐dicarbonyl compounds has been reported. These tandem reactions offer an efficient synthesis of medium‐sized ring or fused‐ring compounds through ring expansion. The methodology has the potential to be widely used throughout organic synthesis due to the easily accessible starting materials and mild reaction conditions. 相似文献
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Synthesis of β‐enaminones from β‐dicarbonyl compounds has been achieved in high yields within a minute using primary and aromatic amines and catalytic amounts of iodine under solvent‐free conditions at room temperature. 相似文献
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Ionic Liquids as Precatalysts in the Highly Stereoselective Conjugate Addition of α,β‐Unsaturated Aldehydes to Chalcones 下载免费PDF全文
Joachim Bijl Prof. Matti Haukka Dr. Henrik Sundén 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(43):13889-13893
Imidazolium‐based ionic liquids (ILs) serve both as recyclable reaction media and as precatalysts for the N‐heterocyclic carbene‐catalyzed conjugate addition of α,β‐unsaturated aldehydes to chalcones. The reaction produces a broad scope of 1,6‐ketoesters incorporating an anti‐diphenyl moiety in high yields and with high stereoselectivity. In recycling experiments, the IL can be reused up to five times with retained reactivity and selectivity. Moreover, the 1,6‐ketoesters form self‐assembled organogels in aliphatic hydrocarbons. The reaction protocol is robust, easily operated, scalable and highly functionalized compounds can be obtained from inexpensive and readily accessible starting materials. 相似文献