An atom economic and external oxidant free methodology has been developed for the synthesis of isoquinolines by Cp*Co(iii) catalyzed annulation of azines via C–H/N–N activation.

Molecular iodine catalysed benzylic sp3 C–H bond amination has been developed for the synthesis of quinazolines from 2-aminobenzaldehydes and 2-aminobenzophenones with benzylamines. The use of oxygen as a green oxidant combined with the transition-metal-, additive- and solvent-free conditions makes the methodology economical and greener. The lack of aqueous work up also enhances the efficiency of this protocol. A series of 2-arylquinazolines was synthesised in good to excellent yields by using the developed protocol. 2-Amino­benzyl alcohols could also be employed to prepare the corresponding quinazoline derivatives.

A green and sustainable methodology for the synthesis of isoquinolines using Ru(ii)/PEG-400 as a homogeneous recyclable catalytic system has been demonstrated. N-Tosylhydrazone, a rarely explored directing group, has been successfully employed for an annulation type of reaction with alkynes via C-H/N-N activation. A short reaction time with a simple extraction procedure, a wide substrate scope with high yields of products, easily prepared substrates, biodegradable solvent, and scalability up to the gram level enhance the efficiency and sustainability of the proposed protocol. Further, the expensive ruthenium-based homogeneous catalytic system could be reused up to a fourth consecutive cycle without any loss in its activity.

Herein, we report an atom‐efficient, rapid, green, and sustainable approach to synthesize isoquinolines and isoquinolinones using a homogeneous recyclable ruthenium catalyst in PEG Media assisted by microwave energy. Dibenzoylhydrazine was used for C–H/N–N activation reactions for the first time in combination with ketazine as oxidizing directing groups for annulation reactions with internal alkynes. The developed protocol is environmentally benign due to significantly shortened times with an easy extraction method, higher atom economy, external oxidant and silver or antimony salt free conditions, applicability to a gram scale synthesis, use of biodegradable solvent and wide substrate scope with higher product yields. Moreover, it is worth noting that the established methodology allowed reuse of the catalytic system for up to five successive runs with minimal loss in activity.

In this work, N-Cbz hydrazone has been employed as a rarely explored directing group for the synthesis of isoquinolines by annulation with internal alkynes via C–H/N–N activation using Ru catalyst. Additive as well as external oxidant-free rapid protocol has been established for the synthesis of isoquinolines using microwave strategy. Use of non-volatile and biodegradable PEG as a green solvent with lower catalyst loading makes the proposed protocol environmentally benign. Further, higher functional group tolerance and wide substrate scope has been observed under the stated methodology with higher yields.