Stereoselective synthesis of highly functionalized tetrahydrocarbazoles through a domino Michael–Henry reaction: an easy access to four contiguous chiral centers

For the first time, a very simple, efficient, mild, catalytic and one-step procedure for the synthesis of a series of densely functionalized 1-methoxycarbonyl-2-aryl-3-nitro-4-hydroxy-1,2,3,4-tetrahydro-9H-carbazole derivatives has been achieved via a domino Michael-Henry reaction of methyl 3-formyl-1H-indole-2-acetates with beta-nitrostyrenes using DABCO as an organocatalyst. Furthermore, the high enantio-(<= 92% ee) and diastereoselective (<= 12 : 1 dr) synthesis of the title compounds has been achieved with excellent yields using 9-O-benzylcupreidine (10 mol%) as a catalyst.