✦ LIBER ✦

Synthesis and chemistry of N-arylated pyrano[2,3-c]pyrazoles

✍ Scribed by J. Geno Samaritoni; Scott Thornburgh; Paul R. Graupner; David H. Cooper

Publisher: Journal of Heterocyclic Chemistry
Year: 2007
Tongue: English
Weight: 340 KB
Volume: 44
Category: Article
ISSN: 0022-152X
DOI: 10.1002/jhet.5570440623

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✦ Synopsis

Abstract

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Novel __N__2‐arylated pyrano[2,3‐c]pyrazol‐6‐ones 2 can be prepared in a selective manner by generating the anion of 1 (RH) with lithium hexamethyldisilazide in DMF and quenching with activated aryl halides. Sterically demanding groups such as phenyl as in 5 reduce reactivity significantly while electronwithdrawing substituents such as trifluoromethyl and phenyl at C4 of the pyranone ring as in 10 and 15 render the pyranone carbonyl particularly susceptible to attack by nucleophiles resulting in ring‐opening to give novel crotonyl derivatives. Proof of structure required a variety of nmr methods involving proton, carbon, and nitrogen nuclei.

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