Novel aryl pyrazole

Recently, the pyrazole group containing bisphenols have been synthesized from activated aromatic dihalides and 3,5-bis (4-hydroxy phenyl)-4-phenyl pyrazole or 3,5-bis(4-hydroxy phenyl)-1,4-diphenyl pyrazole. A novel synthesis of imido aryl containing bisphenols has been reported [32]. N-substituted l,4-bis(4-hydroxy phenyl)-2,3-naphthalimides were prepared from phenolphthalein and copolymerized with aromatic sulfone or ketone difluorides to obtain the poly(imidoaryl ether) sulfones/ ketones. 

Palladium-catalyzed cyclization reactions with aryl halides have been used to synthesize pyrazole derivatives. V-Aryl-lV-(c>-bromobenzyl)hydrazines 26 participated in a palladium-catalyzed intramolecular amination reaction to give 2-aryl-2W-indazoles 27 . Palladium-catalyzed cascade intermolecular queuing-cyclocondensation reaction of o-iodophenol (28) with dimethylallene and aryl hydrazines provided pyrazolyl chromanones 29 <00TL7129>. A novel one-pot synthesis of 3,5-disubstituted-2-pyrazolines 32 has been achieved with an unexpected coupling-isomerization sequence of haloarene 30, propargyl alcohol 31, and methylhydrazine <00ACIE1253>. 

Insuasty B, Tigreros A et al (2010) Synthesis of novel pyrazolic analogues of chalcones and their 3-aiyl-4-(3-aryl-4, 5-dihydro-lH-pyrazol-5-yl)-l-phenyl-lH-pyrazole derivatives as potential antitumor agents. Bioorg Med Chem 18 4965 974... 

Base-promoted reaction of nitrobenzenes 680 with aryl imines 681 afforded arylindazoles 682 (Equation 144) <20000L413>. /3-Tosylhydrazono phosphonates 683, novel and bifunctional reagents, were employed in a concise approach to give polysubstituted pyrazoles 684 in the presence of aromatic and aliphatic aldehydes under basic conditions (Equation 145) <1999SL299>. 

Concurrent with this research was the development of novel pyrazole chemistry which provided a new perspective toward the synthesis of herbicidally active compounds. As depicted in Figure 2, a number of herbicidal l-aryl-5-halo-lIi-pyrazole-4-carbonitriles 7 were prepared (X). A... 

A novel Pd(OAc)2-NFSI-TFA system was developed recently by Xu and cowoilc-ers demonstrating highly selective, ortto-monofluorination. In this case Pd coordination was directed by a diverse range of aryl-Af-heterocyclic directing groups (Scheme 9.15), such as quinoxaline, pyrazole, benzo[rf]oxazole, and pyrazine derivatives. A Pd(ll/IV) catalytic cycle was proposed. 

Some years ago we developed novel families of polydentate hgands of Schiff base and oxime type (L1-L4). Combining at least one imine with oxygen or nitrogen coordination sites (Scheme 1), they facilitate coupling of numerous azole and cyclic amide derivatives (Table 1, entry 1) with aryl bromides under nuld temperature conditions [36-39], [41-43]. With aryl iodides, some reactions were even performed at 25°C and a turnover of about 1,500 was achieved with pyrazole at higher temperature (80°C). This catalytic system is one of the rare examples amongst modem copper chemistry that has already been industrially applied. 

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