Catalytically generated noncovalent ammonium dienolate:a versatile platform for the development of organocatalytic asymmetric cascade reactions

Organocatalytic cascade reactions represent a powerful strategy for the rapid construction of complex chiral molecules with multiple stereocenters from simple substrates under mild conditions. The intriguing structural feature and diverse reactivity of catalytically generated dienolate species render them competent and versatile intermediates for the development of practical and valuable cascade reactions. Over the past years, a plethora of innovative and pioneering noncovalent ammonium dienolatemediated cascade reactions have been designed and implemented under the catalysis of chiral organocatalysts, making dienolate activation a general, robust, and complementary method for the functionalization of unsaturated carbonyl compounds and related substances. This review illustrates the recent advances in organocatalytic noncovalent ammonium dienolate-mediated cascade reactions(mainly from 2010 to 2023), including the cascade transformations of ammonium dienolates directly generated from unsaturated ketone/aldehyde, ester/lactone/azlactone, amide/lactam/pyrazolone/oxindole, and alkylidene nitrile compounds. The contents are arranged based on the reaction types of the ammonium dienolates, with an emphasis on cascade 2,5-, 3,5-, and 4,5-difunctionalizations of these intermediates. Furthermore, other cascade reactions involving the 1,3-, 2,3-, and even more complex 3,4,5-reactivities of ammonium dienolates were also discussed. The reaction pathway, reaction stereoinduction, and synthetic applications of the ammonium dienolate-mediated cascade reactions were highlighted throughout the article. As a stimulating and ever-growing research area, the organocatalytic noncovalent ammonium dienolate-mediated cascade reactions are expected to continue demonstrating their magic power for constructing chiral targets in the future and further expanding the boundaries of asymmetric catalysis.

Catalytic Asymmetric Mannich-Type Reaction Enabled by Efficient Dienolization of α,β-Unsaturated Pyrazoleamides

(E)-α,β-Unsaturated pyrazoleamides undergo facile dienolization to furnish copper(I)-(1Z,3Z)-dienolates as the major in the presence of a copper(I)-(R)-DTBM-SEGPHOS catalyst and EtgN,which react with aldimines to afford syn-vinylogous products as the major dia-stereoisomers in high regio-and enantioselectivities.In some cases,the diastereoselectivity is low,possibly due to the low ratio of copper(I)-(1Z,3Z)-dienolates to copper(I)-(1Z,3E)-dienolates.

Nickel-and Brønsted Acid-Catalyzed Redox-Neutral Coupling of 1,3-Dienes and Aldehydes for Synthesis of Dienols

Dienols are important structural motifs in organic molecules,but most of the traditional synthetic methods required multistep prefunctionalization of substrates,leading to stoichiometric waste and low atom economy.Herein,we report a redox-neutral coupling of simple 1,3-dienes and aldehydes via nickel and Brønsted acid dual catalysis,providing a highly atom-economical and by-product-free route to various dienols with up to 94%yield and up to 50∶1 EE/EZ ratio.The use of 2-isopropoxyphenol as a Brønsted acid co-catalyst was critical to the reactivity and selectivity.

9,10-蒽-3,3′-双(1,3-戊二烯-2,4-二醇)的合成与荧光性质

合成了一种含蒽环的荧光性烯醇化合物——9,10-蒽-3,3′-双(1,3-戊二烯-2,4-二醇),采用核磁共振谱、电喷雾质谱、红外光谱、紫外可见光谱和荧光光谱对该化合物进行结构表征。

基于主要毒效成分的十八反药对甘草与甘遂及其在甘遂半夏汤的配伍研究

目的考察甘草、甘遂在配伍前后及甘遂半夏汤中主要药效成分提取量的变化,从化学成分的角度探索"十八反药对"的配伍规律。方法采用HPLC法测定甘草、甘遂配伍前后及在甘遂半夏汤中甘草酸单铵盐、大戟二烯醇的提取量变化情况。结果甘草酸、大戟二烯醇的提取量随单药→对药→全方的配伍变化,提取量先升高,后降低;但甘草酸升高幅度低于降低幅度,大戟二烯醇升高幅度高于降低幅度。结论甘草与甘遂合煎,其相应毒效成分均明显增加,说明十八反药对甘草与甘遂确实属于配伍禁忌,但二者在甘遂半夏汤复方中相应毒效成分有提取量又均明显降低,说明中医药复方配伍用药确实起到降低毒性的作用,也从化学成分的角度佐证十八反药对只要配伍使用得当也能在临床上起到应有的作用。研究结论为十八反药对自古至今的广泛应用提供了一定的实验依据。