Diastereoselective pot-and atom-economical synthesis of densely-substituted polycyclic 1,2- and 1,2,3-fused indole scaffolds

•One-pot approach to 8,9-dihydropyrido[1,2–a]indol-6(7H)-ones in acceptable yields.•Organobase-catalyzed diastereoselective access to 1,2,3-fused carbocyclic indoles has been realized.•The polycyclic-fused-indoles possessed five contiguous chiral centers.•Pyrrolidine-BzOH/PTSA-catalyzed one-pot synthesis of tetrahydropyrido[1,2–a]indoles was established.