Organocatalytic regiospecific synthesis of 1H-indene-2-carbaldehyde derivatives: suppression of cycloolefin isomerisation by employing sterically demanding catalysts.

The regiospecific synthesis of 1H-indene-2-carbaldehyde derivatives was achieved through transition-metal-free, reductive cyclisation of ortho-formyl trans-cinnamaldehydes with Hantzsch ester in the presence of an aminocatalyst. In particular, cycloolefin isomerisation of the resulting products could be inhibited efficiently by the introduction of a sterically demanding stereo-defined aminocatalyst.