Pd/C-mediated synthesis of α-pyrone fused with a five-membered nitrogen heteroaryl ring: A new route to pyrano[4,3-c]pyrazol-4(1H)-ones

Abstract

Pd/C-mediated alkynylation of 5-iodo-pyrazole-4-carboxylic acid, involving the first regioselective construction of α-pyrone ring on a pyrazol moiety via tandem coupling-cyclization process, has been developed to afford pyrano[4,3-c]pyrazol-4(1H)-one in a single pot. © 2009.