Transition-metal-free chemo-, regio-, and stereoselective synthesis of (Z) and (E) styryl pyrazoles and benzpyrazoles by the addition of N-heterocycles onto functionalized terminal and internal alkynes using a super basic solution of KOH/DMSO has been described. The stereochemical outcome of the reaction was governed by time and quantity of the base. The reaction of pyrazoles and benzpyrazoles onto alkynes takes place chemoselectively without affecting the free −NH₂ group of pyrazoles and −OH group of alkynes. The designed protocol was well implemented on alkynes bearing long alkyl chain, an alicyclic ring, hydroxy, ether, and ester functionality, which offer the N-alkenylated products in good yields. This developed methodology also provides easy access for the synthesis of bis-vinylated heterocycles. The presence of free −NH₂, −OH, −COOR, and halo group in styryl pyrazoles, could be further utilized for synthetic elaboration, which is advantageous for biological evaluation. For the first time, we have disclosed the base-mediated conversion of (Z)-styryl pyrazoles to (E)-styryl pyrazoles in KOH/DMSO system. The cis–trans isomerization was supported by the control experiments and deuterium labeling studies.

中文翻译：

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使用活化和未活化的炔烃进行吡唑/苯并吡唑的化学，区域和立体选择性N-烯化反应

使用KOH / DMSO的超碱性溶液将N杂环加到官能化的末端炔烃和内部炔烃上，可以实现（Z）和（E）苯乙烯基吡唑和苯并吡唑的无过渡金属化学，区域和立体选择性合成。描述。反应的立体化学结果取决于碱的时间和量。吡唑和苯并吡唑在炔烃上的反应是化学选择性发生的，而不会影响吡唑的游离-NH ₂基团和炔烃的-OH基团。所设计的方案在带有长烷基链，脂环族，羟基，醚和酯官能团的炔烃上得到了很好的实现，这些炔烃具有N链烯基化产物，收率高。这种发达的方法学还为合成双乙烯基化杂环提供了便捷途径。苯乙烯基吡唑中存在的游离-NH ₂，-OH，-COOR和卤素基团可进一步用于合成精制，这对生物学评估是有利的。首次，我们公开了在KOH / DMSO系统中由碱介导的（Z）-苯乙烯基吡唑向（E）-苯乙烯基吡唑的转化。顺式-反式异构化得到了对照实验和氘标记研究的支持。