Catalytic Asymmetric Synthesis of Dihydropyrido[1,2‐a]indoles from Nitrones and Allenoates.

An asymmetric method for the synthesis of dihydropyrido[1,2-a]indoles from mixtures of nitrones and allenoates has been developed. This transformation showcases the use of squaramide catalysis in a complicated cascade system that has been shown to be highly sensitive to reaction conditions and substituent effects. The new method provides access to enantiomerically enriched dihydropyridoindoles from modular, non-indole reagents. The optimization and scope of the new transformation is discussed in addition to initial mechanistic experiments that indicate the role of the catalyst.