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.

SummaryA Chan–Lam reaction has been used to prepare N-alkenyl-α,β-unsaturated nitrones, which undergo a subsequent thermal rearrangement to the corresponding tri- and tetrasubstituted pyridines. The optimization and scope of these transformations is discussed. Initial mechanistic experiments suggest a reaction pathway involving oxygen transfer followed by cyclization.

A new cascade reaction provides convergent access to novel bridged bicyclic medium-sized N-heterocycles.

Trans‐isomer‐enriched mixtures can be epimerized to the thermodynamically favoured cis‐isomer‐enriched mixtures (up to 19:1 cis/trans, slight increase in ee) by stirring in methanolic NaOH (25°C, 1 h).