Cobalt(III)‐Catalyzed Synthesis of Fused Quinazolinones by C–H/N–H Annulation of 2‐Arylquinazolinones with Alkynes

Abstract

A convenient and efficient CoIII‐catalyzed cyclization of 2‐arylquinazolinones with alkynes is described. The electron donating as well as withdrawing groups and also halide substituted quinazolinones are compatible with this reaction. This catalytic reaction is highly regioselective with unsymmetrical alkynes. A possible mechanism, involves a formation of five‐membered metallacycle I by metal‐catalyzed aromatic C–H bond activation, alkyne insertion, seven‐membered metallacycle intermediates followed by reductive elimination to give a final product.

Ruthenium‐Catalyzed Synthesis of Macrocyclic Isoquinolines and Isoquinolones via a C−H/N−H Annulations Reaction

“…This result strongly suggests that the CÀ H activation step is reversible. Based on the observed results and reported metal-catalyzed synthesis of isoquinolines and isoquinolones, [5][6][7] and exposure in CÀ N bond formation reactions, [10,13] a suitable mechanism is proposed for the present reaction (Scheme 5). First, the catalytic cycle start with the generation of active ruthenium species Ru II (L)*S n (L = OAc) with CsOAc, which undergo co-ordination with oxime nitrogen of 1 a, followed by the formation of five membered cyclometallated intermediate I with release of HOAc.…”

Recent advances in the synthesis of 2,3-fused quinazolinones

“…In 2019, a highly regioselective Co III -catalyzed C-H/N-H annulation of 2-arylquinazolinones 89 with alkynes 90 to prepare 2,3-fused-quinazolinone derivatives 91 in good yields was developed by Zhang's group (Scheme 49). 50 The reaction was carried out in the presence of 5 mol% [Cp*CoI 2 CO], 10 mol% AgSbF 6 and 1 equiv. of oxidants [Cu(OAc) 2 , and CuO] in DCE at 100 °C.…”

Cp*Co(III)-Catalyzed C–H Hydroarylation of Alkynes and Alkenes and Beyond: A Versatile Synthetic Tool

“…The reaction proceeds efficiently with symmetrical alkynes 28 (Scheme a) and when unsymmetrical coupling partners 34 were employed, the insertion took place regioselectively (Scheme b). When a 3,4-dimethoxyphenyl ring was used as the substituent attached to the quinazoline scaffold ( 39b ), the functionalization took place at the less hindered position, due to the steric hindrance between the substituent and the Cp* ligand of the cobalt (Scheme c) . In this case, to recover the Co­(III) catalyst from the Co­(I) species released after reductive elimination, CuO/Cu­(OAc) 2 had to be added as external oxidants.…”