Copper(II)/Copper(I)-Catalyzed Aza-Michael Addition/Click Reaction of in Situ Generated α-Azidohydrazones: Synthesis of Novel Pyrazolone−Triazole Framework

Abstract

A one-pot Cu(II)-catalyzed aza-Michael addition of trimethylsilyl azide to 1,2-diaza-1,3-dienes and Cu(I)-catalyzed 1,3-dipolar cycloaddition of in situ generated alpha-azidohydrazones with alkynes is reported. This process combining two consecutive steps with recycling of the catalyst (Cu(OAc)(2).H(2)O) represents a useful protocol for the smooth synthesis of novel pyrazolone-triazole derivatives.

Multicomponent Syntheses based upon Copper‐Catalyzed Alkyne‐Azide Cycloaddition

“…[109] This methodology also established the dual role of the copper catalyst in catalyzing both steps. [109] This methodology also established the dual role of the copper catalyst in catalyzing both steps.…”

“…Recently an interesting three‐component methodology transforming 1,2‐diaza‐1,3‐dienes 53 into α‐triazole hydrazones 54 (R 4 =H)/ 54′ (R 4 =TMS) has been established as an aza‐Michael‐CuAAC sequence via α‐azidohydrazone formation (Scheme ) 109. This methodology also established the dual role of the copper catalyst in catalyzing both steps.…”

Synthesis of Highly Functionalized 1,3-Oxathioles via an Unusual [4+1] Annulation of α,α'-Dioxothione with 1,2-Diaza-1,3-dienes

“…Incorporation of all five atoms of the DD skeleton into pyrazolone structures has been successfully applied in our previous work. 12 As four-atom diene synthons, DDs have found application in both [4+1] and [4+2] strategies for the synthesis of dihydropyrazoles 13 and pyridazines, 14 respectively. In addition, they can participate in formal [3+2]-, [4+2]-, and [5+2]-annulation reactions in which two or three ring atoms (C-C or C-C-N) of the azoene component are incorporated in the final cycloaddition products.…”

“…During ongoing studies, we came to appreciate the advantages of diverse 1,2-diaza-1,3-dienes (DDs, 3; Figure 1). [11][12][13][14][15] In particular, we found that conjugated azoenes with electron-withdrawing substituents (e.g., esters or amides) on the terminal carbon and/or nitrogen (Figure 1), were particularly suitable as versatile synthetic building blocks because of their five-atom (3C + 2N) C4-electrophilic nature, dense substitution patterns, and flexible functionality that was capable of undertaking multiple roles. Generally, DDs can afford one to five atoms to construct cyclic molecules.…”

Copper‐catalyzed Synthesis of N‐alkylated 2‐(4‐substituted‐1H‐1,2,3‐triazol‐1‐yl)‐1H‐indole‐3‐carbaldehyde by Step‐wise and One‐pot Three‐component Huisgen's 1,3‐dipolar Cycloaddition Reaction

“…Favi et al reported one‐pot copper (II)‐catalyzed Aza–Michael addition of trimethylsilyl azide to 1,2‐diaza‐1,3‐dienes and copper(I)‐catalyzed 1,3‐dipolar cycloaddition of the in situ generated α ‐azido hydrazones with alkynes . However, alkynes are the most commonly used starting materials that can provide a carbon framework.…”