Povarov MCRs

A solid-phase Ugi-Reissert reaction on chloroformate resin, has been reported. The product, the ot-carbamoylated isoquinoline 230, is released by oxidative cleavage (Scheme 33a). Interestingly, the enamide moiety in the adduct can be exploited to perform this process in tandem with a Povarov MCR [189, 190]. In this way, by interaction of dihydroisoquinoline 231 with aldehydes, anilines and a suitable Lewis acid catalyst, the polyheterocyclic system 232 was prepared (Scheme 33b). The Zhu group devised an innovative approach for the synthesis of this class of compounds. They employed the heterocyclic amine 233, which was oxidized in situ to the dihydroisoquinoline 234 with IBX, to undergo the classic Ugi reaction. Remarkably, all the components are chemically compatible, allowing the sequence to proceed as a true MCR (Scheme 33c) [191]. 

ESSENTIAL MULTICOMPONENT REACTIONS n 13.4 POVAROV MCRs 13.4.1 Introduction... 

The next important class comprises non-isocyanide-based MCRs. In contrast to IMCRs, non-isocyanide-based MCRs do not rely on the unique properties of isocyanides, but rather rely in most cases on the reactivity of imines generated in situ from amines and aldehydes. This class includes the Gewald reaction [4], the Hantzsch reaction [6], the Biginelli reaction [3], the Petasis reaction [47 9], the Kabachnik-Fields reaction [8, 9], the Povarov reaction [50], and the Doebner reaction [51]. 

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