کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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5213534 | 1383160 | 2016 | 9 صفحه PDF | دانلود رایگان |
The reactivity of 1-(2-bromobenzyl)-4-halopyrazoles in inter- and intra-molecular Pd-catalysed direct arylation was investigated. Conditions allowing the intermolecular C5-arylations of both 1-(2-bromobenzyl)-4-chloropyrazoles and 1-(2-bromobenzyl)-4-bromopyrazoles, without cleavage of the pyrazolyl and benzyl C-halo bonds, are reported. Using KOAc as the base, DMA as the solvent and 2 mol % of an air stable palladium catalyst, the target C5-arylated pyrazoles were obtained in moderate to good yields with a wide variety of aryl bromides. The synthesis of 3-halopyrazolo[5,1-a]isoindoles via intramolecular Pd-catalysed direct arylation, without cleavage of the pyrazolyl C-halo bonds is also described. Moreover, sequential Pd-catalysed C5-arylations followed by intramolecular direct arylation allowed the access to dibenzo[c,e]pyrazolo[1,5-a]azepine derivatives. The reactivity of the 2-bromobenzyl moiety of C5-arylated 1-(2-bromobenzyl)-4-halopyrazoles in intermolecular direct arylation or in Suzuki coupling is also described.
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Journal: Tetrahedron - Volume 72, Issue 29, 21 July 2016, Pages 4312-4320