Synthesis of Multi‐substituted Dihydropyrazoles by Copper‐Mediated [4+1] Cycloaddition Reaction of N‐Sulfonylhydrazones and Sulfoxonium Ylides

Abstract

A general and expeditious approach for the copper mediated synthesis of multi‐functionalized dihydropyrazoles from N‐sulfonylhydrazones and sulfoxonium ylides has been achieved under aerobic oxidative conditions. The formal [4+1] cycloaddition reaction exhibits many notable features and can be easily scaled up to gram scale.

Synthesis of Polycyclic Fused Indoline Scaffolds through a Substrate-Guided Reactivity Switch

“…By taking advantage of the unique reactivity of DDs 10 and intrigued by these and our recent findings in the manipulation of indolyl cores, 11 we reasoned that the proper combination of indole and 1,2-diaza-1,3-diene elements might allow us to design a substrate-controlled divergent approach. In this design, DDs would be used as C2N1 or C2N2 units (1,3 or 1,4 dipole synthons) to realize [3 + 2] and [4 + 2] annulation reactions of indoles, respectively ( Scheme 1 ).…”

Metal‐Free Synthesis of 5‐Trifluoromethyl‐1,2,4‐Triazoles from Iodine‐Mediated Annulation of Trifluoroacetimidoyl Chlorides and Hydrazones

“…Further optimization towards the reaction temperature was implemented and the reaction was carried out at room temperature, 60°C and 100°C, respectively. The inferior results were obtained compared with that of 80°C (Table 1, entries [12][13][14]. Decreasing the amount of I 2 to 0.5 equivalent resulted in the decrease of reaction yield and a slight increase of the reaction efficiency could be achieved when 1.5 equivalents of I 2 was used in the second step (Table 1, entries [15][16].…”

“…(Scheme 1c). [12] Encouraged by the above fruitful works and our continuous endeavors on the synthesis of structurally diverse nitrogen-containing heterocycles, [13] we present herein an efficient metalfree multistep coupling reaction of trifluoroacetimidoyl chlorides and hydrazones for the rapid preparation of 5-trifluoromethyl-1,2,4-triazoles (Scheme 1h). [9] Additionally, transition-metalcatalyzed transformations of trifluoroacetimidoyl halides with alkynes for the construction of 2trifluoromethyl quinolones have also been extensively investigated (Scheme 1e).…”

“…Noteworthy was that the reports about the synthesis of perfluoroalkyl-1,2,4-triazoles were quite rare, which involved the hydrazinolysis reaction of 5-perfluoroalkyl-1,2,4-oxadiazoles or the conversion of the 2-chloro-1,1,1-trifluoro-2-propyl azo compound. The inferior results were obtained compared with that of 80°C (Table 1, entries [12][13][14]. [15] Initially, we chose 2,2,2-trifluoro-N-(p-tolyl)acetimidoyl chloride 1 b and hydrazone 2 a as the model substrates for our investigation.…”

“…(Scheme 1g). [12] Encouraged by the above fruitful works and our continuous endeavors on the synthesis of structurally diverse nitrogen-containing heterocycles, [13] we present herein an efficient metalfree multistep coupling reaction of trifluoroacetimidoyl chlorides and hydrazones for the rapid preparation of 5-trifluoromethyl-1,2,4-triazoles (Scheme 1h). Noteworthy was that the reports about the synthesis of perfluoroalkyl-1,2,4-triazoles were quite rare, which involved the hydrazinolysis reaction of 5-perfluoroalkyl-1,2,4-oxadiazoles or the conversion of the 2-chloro-1,1,1-trifluoro-2-propyl azo compound.…”