C–H Activation-Engaged Synthesis of Diverse Fused-Heterocycles from the Reactions of 3-Phenyl-1,2,4-oxadiazol-5(2H)-ones with Vinylene Carbonate

Abstract

We report the condition-controlled C–H activation-engaged reactions of 3-phenyl-1,2,4-oxadiazol-5­(2H)-ones with vinylene carbonate, straightforwardly constructing four divergent fused-heterocycles by tuning the reaction conditions in a one-pot manner.

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

“…In 2022, Wu and coworkers developed a divergent C–H [4 + 2] conversion of 3-phenyl-1,2,4-oxadiazol-5(2 H )-one with VC under a rhodium catalyst, which resulted in an array of hydroxyisoquinolin-oxadiazones 49 , isoquinolin-oxadiazones 50 , and 1-isoquinolinamines 51 according to the different additives and even reaction atmospheres (Scheme 15). 61 Most impressively, this protocol led to a series of isoquinolin-1-amine alkaloids widely found in natural products and pharmaceuticals. The divergent synthesis with broad substrate scope and high efficiency made it more beneficial for chemical derivatization.…”

“…As shown in Scheme 37, Wu also found that substrates 3-phenyl-1,2,4-oxadiazol-5(2 H )-ones 115 were capable of reacting with two VC units in a rhodium catalytic system, yielding structurally more attractive imidazo[2,1- a ]isoquinoline 116 . 61 A series of control experiments demonstrated that intermediate 115-I and 1-isoquinolinamines 115-II were probably the key intermediates. The authors also speculated that higher temperature might lead to the instability of 115-I , thus enabling subsequent decarboxylation toward the primary aniline species 115-III , which finally resulted in the formal [3 + 2] annulated product 116 .…”

Synthesis of 1H-Isochromenes via Iridium-Catalyzed Cascade C–H Activation/Annulation of Pyridotriazoles at Room Temperature

“…Recently, we have disclosed a C–H activation/annulation cascade reaction with iodonium ylides . Given that our group are committed to develop efficient synthetic routes of C–H activation and carbenoid insertion reactions, − we anticipated that 3-phenyl-pyridotriazole could react with diazodicarbonyl compounds via transition metal-catalyzed C–H activation followed by sequent denitrogenation and insertion into the O–H bond to construct fused isochromene scaffolds. If successful, this cascade intramolecular annulation combining C–H activation and carbene insertion would provide oxygen-containing heterocycles in an efficient one-pot manner and expand the utility and transformations of pyridotriazoles.…”

Rh(iii)-catalyzed C(sp2)–H functionalization/[4+2] annulation of oxadiazolones with iodonium ylides to access diverse fused-isoquinolines and fused-pyridines

“…Interestingly, the reaction of 4a at the catalyst of [Cp*RhCl 2 ] 2 /AgOAc could deliver the aminophenanthridin compound 6 in 84% yield. 11 And treatment of 4a with 2 equivalents of KOH in ethanol could afford a new isoquinoline compound 7 in 77% yield at 80 1C. Next, preliminary mechanistic studies were conducted to gain insight into the possible reaction mechanism (Scheme 4-4).…”

“…Since Zhu et al reported a cyclization of 3-aryl-1,2,4-oxadiazolones with internal alkynes as coupling partners, allowing the synthesis of aminoisoquinolines in 2016, 9 these substrates have become important building blocks to construct substituted polyheterocycles. For instance, Rh( iii )-catalyzed oxadiazolone-directed alkenyl C–H activation/annulation with multiple types of alkynes, 10 vinylene carbonate, 11 and α-diazo carbonyl, 12 have been reported. Despite these achievements, the applications in constructing structurally diverse polyheterocycles are still in their infancy.…”