Direct Synthesis of Pyrazolo[5,1-alpha]isoindoles via Intramolecular Palladium-Catalyzed C-H Bond Activation

Abstract

An efficient. direct synthesis of pyrazolo-[5.1-alpha]isoindoles employing a palladium-catalyzed intramolecular C-H bond activation of 1-(2-halobenzyl)pyrazoles has been developed The use of lithium chloride (LICI) was found to be essential in these reactions, to suppress further C H bond activation at the C-3 position of pyrazolo[5,1-alpha]isoindole, when C-3 is unsubstituted This protocol can be applied to the synthesis of a pyrazolo(5,1-alpha]isoqumnoline possessing a six-membered central ring system and a fully substituted pyrazolo[5,1-alpha]isoindole using seciuential intra- and intermolecular C-H bond activation