Synthesis of Heteroaryl Triazenes via Rh(III)‐catalyzed Annulation Reactions with Alkynyl Triazenes

Abstract

A synthetic route towards polycyclic heteroaryl triazenes has been developed. Alkynyl triazenes were coupled to phenyl-substituted indoles, imidazoles and sydnones via rhodium-catalyzed double CÀH or CÀH/NÀH activation reactions. The oxidative annulations gave triazenes connected to imidazo[1,2-a] quinoline, indolo[2,1-a]isoquinoline and sydnone-quinoline scaffolds in moderate to excellent yields. The triazene-bearing fused sydnone-quinolines were used for subsequent orthogonal transformations. The sydnone moiety allowed for post-functionalization via 1,3-dipolar cycloadditions in excellent yields, and the triazene group can be substituted by a range of functional groups.

Vinyl and Alkynyl Triazenes: Synthesis, Reactivity, and Applications

“…[27] In order to access polycyclich eteroaryl triazenes,a lkynyl triazenes were coupled to phenyl-substituted imidazoles, indoles,a nd sydnones by Cp*Rh-catalyzed double CÀHo r C À H/N À Ha ctivation reactions (Scheme 10 A). [28] Forr eactions with phenyl-substituted imidazoles and indoles,t he yields (49-82 %) were affected to some extend by degradation of the acid-sensitive alkynyl triazenes.B etter yields were obtained for reactions with phenylsydnone,which could be performed under milder conditions (RT). The resulting coupling products were used for subsequent orthogonal transformations (Scheme 10 B).…”

“…The resulting coupling products were used for subsequent orthogonal transformations (Scheme 10 B). [28] Thes ydnone moiety allowed for post-functionalization via 1,3-dipolar cycloadditions,w hereas the triazene group could be substituted by ar ange of functional groups (e.g. azide,b romide,o ri odide).…”

Vinyl and Alkynyl Triazenes: Synthesis, Reactivity, and Applications

“…In order to access polycyclic heteroaryl triazenes, alkynyl triazenes were coupled to phenyl‐substituted imidazoles, indoles, and sydnones by Cp*Rh‐catalyzed double C−H or C−H/N−H activation reactions (Scheme 10 A). [28] …”

“…The resulting coupling products were used for subsequent orthogonal transformations (Scheme 10 B). [28] The sydnone moiety allowed for post‐functionalization via 1,3‐dipolar cycloadditions, whereas the triazene group could be substituted by a range of functional groups (e.g. azide, bromide, or iodide).…”

Rhodium(III)‐Catalyzed Dehydrogenative Annulation of 2‐Arylindazoles with Cyclic Enones

“…Recently, the transition metal‐catalyzed ortho ‐C–H bond functionalization of aryl ring has evolved as a powerful tool in organic synthesis [7] . In particular, 2‐arylindazoles have successfully been functionalized with α‐diazocarbonyl compounds, [8] 2‐alkynylanilines, [9] alkynyl triazenes, [10] 1,2‐disubstituted alkynes [11] dioxazolone [12] and maleimides etc [13] . However, this is the first report using 2‐arylindazoles with cyclic enones.…”