Regioselective [3+2]‐Spiroannulation and [4+n]‐Annulation Approaches through Activation of C−H Bond Facilitated by Ru(II) as Catalyst: Role of Solvent Selectivity

Abstract

Ru(II)‐catalyzed and solvent‐switched [3+2]‐spiroannulation and [4+n] (n=1, 2, 3) annulations of 2‐aryl quinazolinone or 2‐aryl‐2,3‐dihydrophthalazine‐1,4‐diones with ynones or alkynyl alcohol or 1,3‐diynes under mild reaction conditions have been analyzed. These reactions take the course in presence of proper solvent candidate and features redox‐neutral pathway. Ynone, serves as an ‘atypical one‐carbon unit’ in [4+1] annulation and generates quaternary carbon center bearing diverse heterocycles through [3+2] and [4+1] annulation strategies. Post transformations of the synthesized spiro‐products augments the potential of the developed methodology.

Harnessing the benzyne insertion consequence to enable π-extended pyrido-acridine and quinazolino-phenanthridine

“…In the case of the deaminative coupling process, the quinazolimine 4a is converted to 4a′ (characterized by 1 H-NMR, ESI‡) in the presence of p -toluenesulfonic acid and t BuONO. 11 Then, the diazonium ion 4a′ interacts with the Pd( ii ) species through an oxidative addition pathway and generates the intermediate M . Then, the Pd centre interacts with the adjacent phenyl ring to generate the intermediate N .…”