Lewis Base‐Catalyzed Cycloaddition of Heterocyclic Alkenes with 2,2,2‐Trifluorodiazoethane (CF₃CHN₂): Access to Trifluoromethylated Pyrazolines and Pyrazoles

Abstract

An efficient Lewis base catalytic protocol to biologically important trifluoromethylated pyrazolines and pyrazoles is developed through triazene-heterocyclic alkene cycloaddition reactions of an array of oxa-/aza-benzonorbornadienes and coumarins with CF 3 CHN 2 . This triazene-heterobicyclic alkene cycloaddition procedure features good functional group tolerance, scaffold diversity, and feasible late-stage functionalization of some representative natural products.

Strategies and Methods for the Synthesis of 2‐Pyrazolines: Recent Developments (2012–2022)

“…by the cycloaddition reactions of heterobicyclic alkenes 117 and CF 3 CHN 2 (Scheme 24a). While all of the Lewis bases used for the preparation provided satisfactory yields, it was found that DBU could more efficiently promote the reaction [49a] . Very recently, Cao et al.…”

Trifluorodiazoethane: A versatile building block to access trifluoromethylated heterocycles

“…In 2021, Wang's group documented a DBU‐catalyzed [3 + 2]‐cycloaddition of CF 3 CHN 2 with strained bicyclic alkenes 45 to access fused pyrazolines 46 (Scheme 24) [46]. This base‐catalyzed protocol was compatible with a number of oxa−/aza ‐benzonorbornadienes 45 to efficiently deliver the targeted products 46 in good to excellent yields.…”

Chemoselective and diastereodivergent synthesis of new spirooxindolo-pyrrolizidines and pyrrolidines stemming from unsymmetrical 1,3-bis(arylidene)tetral-2-ones: a combined experimental and theoretical study

“…In this context, the cycloaddition reaction is conceptually the most adopted synthesis approach to reach heterocyclic compounds. [1][2][3] This basic reaction despite being known for quite a while still solicits the attention of many researchers, 4,5 since it occurs most often with sufficiently high yields 6,7 and proceeds with an interesting diastereo-and enantio-selectivity 8,9 to provide access to a wide range of hybrid products that are hard to reach by other synthetic routes. Several variants of this reaction have emerged, and in the few last years, a new concept has been developed: the one-pot cycloaddition reaction 10 which turns it into a real synthetic masterpiece compared to domino reactions because it allows a significant reduction of the required time as well as skips all intermediate steps of purification.…”