Synthesis of 3-Carboxylate Indazoles via Ru(II)-Catalyzed Annulation of Azobenzenes with Ethyl Glyoxalate

Organozincs for versatile synthesis of non-symmetric azoarenes

“…26 During the last few decades, chelation-assisted transition metal-catalyzed C–H activation has emerged as a powerful tool for the synthesis of complex molecules, and we herein also showed the easy transformation of azoarene into heterocyclic compound 50 via ruthenium-catalyzed [4 + 1] cyclization with ethyl 2-oxoacetate. 27 Finally, treatment of azoarene 32 with n -butyllithium delivered trisubstituted hydrazine 51 in 66% yield (Scheme 5c). 28 Overall, these results showed the applicability of our technology to medicinal chemistry and organic synthesis.…”