Organocatalytic formal [5+1] annulation: diastereoselective cascade synthesis of functionalized six-membered spirocyclic indane-1,3-diones/oxindoles via Michael-aldol reaction

An efficient cascade protocol has been developed for the diastereoselective synthesis of functionalized six-membered spirocyclic compounds. The reaction proceeded smoothly between indane 1,3-diones/oxindoles/coumaranone as the dinucleophilic components and (E)-5-nitro-6-aryl-hex-5-en-2-one as the dielectrophile to give the desired products with reasonable to high chemical yields (30-84%) and high levels of diastereoselectivities (upto >95:5 dr). The reaction proceeded smoothly via cascade Michael aldol reaction. (C) 2013 Elsevier Ltd. All rights reserved.