Synthesis of Diverse Fused Pyrazoles through Palladium‐Mediated Heteroarylation of Heteroarene C–H Bonds

Abstract

A facile and efficient synthesis of new fused pyrazoles through the Pd(OAc)2‐mediated heteroarylation of heteroarene C–H bonds in Morita–Baylis–Hillman derivatives of 4‐iodopyrazolecarbaldehydes is described.

Exploration of pyrazole based aldo‐x bifunctional building blocks for the synthesis of pyrazole annulated molecular architectures

“…The Morita‐Baylis‐Hillman acetates 87 afforded from these pyrazole based aldo‐x precursors were utilized for the stereoselective synthesis of pyrazolo[4,3‐ c ]pyrrolo[1,2‐ a ]azepines 112 and pyrazole‐azepino[1,2‐ a ]indoles 114 as displayed in Scheme 27. [ 42 ] Under this study, the MBH acetates 87 were treated with NH 3 ‐MeOH to afford the allyl amines 110 , which were further reacted with 2,5‐dimethoxytetrahydrofuran in the presence of AcOH to install the pyrrole functionality. The ( E ) stereochemistry of substrate 110 was required to facilitate the intramolecular heteroarylation reaction.…”

Palladium(II) Acetate

“…, CuI DMF, 140 °C, 48 h PhMe, 110 °C, 16 hSeven-membered fused pyrazole moieties can be accessed through a standard palladium-catalyzed intramolecular direct arylation of pyrroles or indoles with iodopyrazoles (eq 168) 302. …”