An easy direct arylation of 5-pyrazolones

Abstract

SummaryA mild, efficient and catalytic ligand-free method for the direct arylation of 5-pyrazolones by Pd-catalyzed C–H bond activation is reported. The process smoothly proceeds and yields are moderate to excellent.

Polyfluoroalkylated antipyrines in Pd-catalyzed transformations

“…The literature data analysis has shown that antipyrine and its non-uorinated analogs readily undergo the Pd-catalyzed direct arylation with the different arylhalogenides. 46,47 However, our numerous efforts to involve 5-triuoromethyl-antipyrine 1a into the direct arylation with arylhalogenides were ineffective, despite the use of various palladium catalysts {Pd(OAc) 2 , Pd 2 (dba) 3 }, bases (AcOK, K 2 CO 3 , Cs 2 CO 3 , K 3 PO 4 ), ligands (ligand-free, XPhos), solvents (CO(OEt) 2 , EtOH-H 2 O, DMA, toluene, 1,4-dioxane), temperature modes (100-160 C) and ratios of reagents in these reactions. The extended experiments are presented in Table S1 (please see, ESI †).…”

“…56 It explains the weak reactivity of compound 1a in the reactions of electrophile arylation comparing to the non-uorinated antipyrine in analogous transformations. 46,47 Then, we investigated the possibility of modifying polyuoroalkyl-antipyrines 1 at the center C4 in the Pdcatalyzed Suzuki and Sonogashira cross-coupling reactions. At rst, 4-bromo-5-polyuoroalkyl-antipyrines 4a-d and 4-iodo-5-polyuoroalkyl-antipyrines 5a, b were synthesized by the treatment of the initial heterocycles 1a-d with N-bromo-or N-iodosuccinimide (NXS) (Scheme 2).…”

Metal‐Free Direct C–H Thiolation and Thiocyanation of Pyrazolones

“…Other solvents and oxidants including Na 2 S 2 O 8 , (NH 4 ) 2 S 2 O 8 or peroxide (i.e. H 2 O 2 , TBHP, DTBP) were less effective for this transformation (entries [7][8][9][10][11][12]. [15] Carrying out the reaction at room temperature resulted in much lower conversion (entry 13).…”

“…Throughout the past decade, good progress has been made toward the direct C–C bond coupling of bioactive pyrazolone cores (such as phenazone) via C–H functionalization. These examples include Pd‐catalyzed direct arylation and alkenylation, Au‐catalyzed alkynylation of pyrazolones with hypervalent iodide, Cu‐promoted direct acylation reactions as well as Ru‐catalyzed oxidative double C–H activation and annulation reaction . On the other hand, the direct carbon–heteroatom bond coupling of N ‐substituted pyrazolone compounds has not been found in literature until recently.…”

A palladium-catalyzed cascade approach for the synthesis of 3,3a,4,6,7,8,9,9a-octahydro-1H-benzo[f]isoindole-1,5(2H)-diones

“…[6][7][8][9][10] Recently, the α-arylation of enones and their derivatives has been developed. [11][12][13][14] For example, Liu reported an efficient synthesis of N-fused polycyclic indoles via a palladium-catalyzed annulation/ acyl migration cascade reaction (Scheme 1a). 11 McGlacken reported that 1,3-diketone-derived enol ethers could undergo Heck cyclization, offering tricyclic oxoisochromene derivatives in good yields (Scheme 1b).…”