Divergent Reactivity of Nitrocyclopropanes with Huisgen Zwitterions and Facile Syntheses of 3‑Alkoxy Pyrazolines and Pyrazoles

A novel
annulation reaction of trans-2-substituted-3-nitrocyclopropane-1,1-carboxylates
with in situ generated Huisgen zwitterions is reported, providing
facile synthesis of 3-alkoxy pyrazolines in good yields and high diastereoselectivities.
This reaction unveils the divergent reactivity of the nitrocyclopropanes
as a kind of versatile donor–acceptor cyclopropanes. It is
also demonstrated that the prepared 3-alkoxy pyrazolines from di-tert-butyl azodicarboxylate can be readily transformed into
the corresponding 3-alkoxy 1H-pyrazoles in moderate
yields.

本文报道了一种新型环化反应：反式-2-取代-3-硝基环丙烷-1,1-二羧酸酯与原位生成的休根两性离子(Huisgen zwitterions)发生反应，可便捷合成3-烷氧基吡唑啉，产物收率良好且非对映选择性优异。该反应揭示了硝基环丙烷作为一类多功能给体-受体环丙烷的多样反应活性。研究同时证实，由偶氮二甲酸二叔丁酯制备得到的3-烷氧基吡唑啉，可在中等收率下方便地转化为相应的3-烷氧基-1H-吡唑。