Multicomponent reaction heterocyclic systems

Nair V, Vinod AU, Abhilash N et al (2003) Multicomponent reactions involving zwitterionic intermediates for the construction of heterocyclic systems one pot synthesis of aminofurans and iminolactones. Tetrahedron 59(51) 10279-10286... 

A promising combination of sequential multicomponent Ugi reaction and INOC has been carried out for the preparation of fused isoxazoles and isoxazolines (413). The coupling of these two reactions (Scheme 1.38) provide access to the heterocyclic ring systems in two steps, from easily available starting materials (e.g., R = Ph, R/=PhCH2), in moderate to good overall yields (the yields of Ugi reaction products 354 were 50%-70%, those of the INOC products 355 were 27%-64%). 

Another type of multicomponent [2 + 2+1] cycloaddition is achieved with diazo carbonyl compounds in the presence of rhodium or copper catalysts. Reaction with additional carbonyl groups within the substrate gives carbonyl ylides. These, as formal 1,3-dipoles, can undergo [3 + 2] cycloaddition with alkenes or alkynes to form heterocyclic ring systems,7 83... 

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