Rhodium‐Catalyzed Synthesis of Isoquinolino[1,2‐b]Quinazolines via C−H Annulation in Biomass‐Derived γ‐Valerolactone

Abstract

A rhodium-catalyzed synthesis of isoquinolino [1,2-b]quinazolines via CÀ H annulation using vinylene carbonate as an oxidizing acetylene surrogate in biomassderived γ-valerolactone (GVL) has been developed. The reactions proceeded smoothly to give the corresponding products in moderate to good yields without any external oxidant and base. This protocol can also be applied for the synthesis of 5,6-dihydro-8H-isoquinolino[1,2-b]quinazolin-8ones.

Derivation of Benzothiadiazine‐1,1‐dioxide Scaffolds via Transition Metal‐Catalyzed C—H Activation/Annulation

“…Based on the above mechanism experiments and previous literatures, [ 31,34‐35 ] possible mechanism of two reactions is proposed in Scheme 4. As for the reaction with vinylene carbonate (Scheme 4a), firstly an active catalyst Ru is formed in the presence of AgNTf 2 , then cyclometalation between catalyst and tautomerized 1a affords a five‐membered ruthenacycle intermediate A .…”

“…[ 31‐33 ] On the other hand, vinylene carbonate has been reported as a practical acetylene surrogate to form annulate products in many reactions. [ 34‐35 ] Given that using the 1,2,4‐benzothiadiazine‐1,1‐dioxide as a directing group has been rarely explored, we envisage that the annulation of benzothiadiazine‐1,1‐dioxides with vinylene carbonate or diazopyrazolone via C—H activation could provide a series of novel structures, which can enrich the library of benzothiadiazine‐1,1‐dioxides.…”

Advancement of vinylene carbonate as a coupling partner in metal-catalyzed C–H functionalization

“…59 Besides the common cyclization products, the Zhang group, in 2021, used GVL and alcohol as green solvents to obtain esterification products in the reaction system of rhodium-catalyzed [4 + 2] cyclization between 2-arylquinazolinones and VC. 60…”

Divergent Protocol for the Synthesis of Isoquinolino[1,2-b]quinazolinone and Isoquinolino[2,1-a]quinazolinone Derivatives

“…Therefore, the development of efficient, step-economic, and modular methods to access this system is particularly needed. To this end, many synthetic methods for their access have been reported including the annulation reactions of 2-arylquinazolinones, a Pd-/Cu-catalyzed aerobic oxidation to deliver dihydrofuran fused to isoquinolino­[1,2- b ]­quinazolinones, a Pd-catalyzed annulation of 2-phenylquinazolin-4­(3 H )-ones with diaryliodonium salts to furnish aryl-fused isoquinolino­[1,2- b ]­quinazolinones, and a Rh-catalyzed synthesis of isoquinolino­[1,2- b ]­quinazolines via C–H annulation with vinylene carbonate on 2-arylquinazolinones . Additionally, Wang and coworkers have reported the synthesis of isoquinolino­[1,2- b ]­quinazolin-8-ones using a CuI-catalyzed reaction (Scheme a) .…”