Selective Construction of Spiro or Fused Heterocyclic Scaffolds via One-pot Cascade Reactions of 1-Arylpyrazolidinones with Maleimides

Abstract

Presented herein is a controllable selective construction of spiro or fused heterocyclic scaffolds through the onepot cascade reactions of 1-phenylpyrazolidinones with maleimides. To be specific, succinimide spiro pyrazolo[1,2-a]pyrazolones were effectively formed via [4 + 1] spiroannulation of 1-phenylpyrazolidinones with maleimides through simultaneous C(sp 2 )-H bond activation/functionalization and intramolecular cyclization along with the traceless fusion of the pyrazolidinonyl unit into the final product. In this reaction, air acts as a cost-effective and environmentally sustainable oxidant to assist the regeneration of the Rh(III) catalyst. Alternatively, succinimide-fused pyrazolidinonylcinnolines were formed from the same starting materials through an initial [4 + 1] spiroannulation followed by basepromoted skeleton rearrangement of the in situ formed spiro product without isolation. Notable features of these protocols include easily tunable selectivity, broad substrate scope, cost-effective and sustainable oxidant, excellent atom economy, and facile scalability.

C–H activation-initiated spiroannulation reactions and their applications in the synthesis of spirocyclic compounds

“…29 The spiroannulation reactions of 1-phenylpyrazolidinones with maleimides have also been realized to give spiro pyrazolo [1,2-a]pyrazolones in good efficiency (Scheme 36). 30 Moreover, the NH unit in N-( phenylsulfonyl)acetamides was viable in assisting the CHA reaction with maleimides to give succinimide spiropyrazolo[1,2-a]pyrazolones (Scheme 37). 31 The formation of the product involves the generation of a five-membered rhodacycle via C-H activation, coordination with maleimide, migratory insertion, isomerization, β-hydride elimination, reductive elimination and aza-Michael addition (Scheme 37).…”

“…The spiroannulation reactions of 1-phenylpyrazolidinones with maleimides have also been realized to give spiro pyrazolo[1,2- a ]pyrazolones in good efficiency (Scheme 36). 30…”

Recent advances in spirocyclization of maleimides via transition-metal catalyzed C–H activation

“…As ] 2 catalyzed spirocyclization method, utilizing 1-arylpyrazolidinones 179 as directing groups with maleimides 16 in DCE medium in the presence of Zn(OAc) 2 as displayed in Scheme 45. 39 In the optimization study several additives such as AgOAc, Na 2 CO 3 , K 3 PO 4 , NaOAc, KOAc, LiOAc, CsOAc, AcOH, PivOH and Zn(OAc) 2 were screened where Zn(OAc) 2 was found to be the best additive in terms of product yield.…”

“…Recently, Li et al developed a [RhCp*Cl 2 ] 2 catalyzed spirocyclization method, utilizing 1-arylpyrazolidinones 179 as directing groups with maleimides 16 in DCE medium in the presence of Zn(OAc) 2 as displayed in Scheme 45. 39 In the optimization study several additives such as AgOAc, Na 2 CO 3 , K 3 PO 4 , NaOAc, KOAc, LiOAc, CsOAc, AcOH, PivOH and Zn(OAc) 2 were screened where Zn(OAc) 2 was found to be the best additive in terms of product yield. Apart from [RhCp*Cl 2 ] 2 , several metal catalysts such as [Ru( p -cymene)Cl 2 ] 2 , CoCp*(CO)I 2 , [IrCp*Cl 2 ] 2 and [Rh(COD)Cl] 2 have been screened but all these catalysts failed to give the product.…”

Synthesis of structurally diverse pyrazolo[1,2-a]pyrazolones based on the selective C–H bond alkenylation–annulation of 1-arylpyrazolidinones with allenyl acetates

“…Inspired by the above-described pioneering studies and as a continuation of our research interest in CHA-initiated cascade reactions, 9,10 especially by using allene derivatives as effective CPs, 8 i we conceived a reaction between 1-arylpyrazolidinones and allenyl acetates with the aim of developing alternative approaches towards fused N -heterocyclic compounds. Herein, we would like to report the results obtained in this regard.…”