Entwicklung neuer Dominoreaktionen durch Michael-Addition an Nitroalkene als Schlüsselschritt

In this dissertation organocatalytic cascades consisting of a Michael-addition and hemiacetalization or hemiaminalization between aldehydes and nitrovinyl phenoles or nitrovinyl indoles have been developed for the synthesis of various heterocycles. These domino reactions start with an enamine-or a dienamine-mediated Michael-addition, which is followed by an intramolecular hemiacetalization or hemiaminalization. The hemiacetals or hemiaminals obtained were successfully converted to the corresponding cis-3,4-disubstituted chromanes, coumarins or 1H-pyrrolo [1,2-a]indol-3(2H)-ones in good to very good yields and high stereoselectivities through BF3•Et2O-mediated dehydroxylation or PCC-mediated oxidation. Furthermore, a domino oxa-Michael/Michael reaction between nitrovinyl phenoles und acrolein has been developed, which proceeds according to the iminium/enamine-activation sequence. Based on this protocol trans-3,4-disubstituted chromanes were obtained in good to very good yields and excellent stereoselectivities. The domino product could be readily converted to Nalkylated benzopyrano[3,4-c]pyrrolidin through reductive amination and N-alkylation, which is contained as a characteristic structure in numerous biologically active compounds