Enantioselective Synthesis of Cyclopentene Carbaldehydes by a Direct Multicatalytic Cascade Sequence: Carbocyclization of Aldehydes with Alkynes

The reaction of α, βunsaturated aldehydes 1 with alkyne-tethered nucleophiles, such as malononitriles and cyanoacetates, in a highly enantio- and diastereoselective iminium-enamine-Lewis acid catalyzed cascade sequence to produce cyclopentene carbaldehydes of broadhas been reported. A major driving force for the many new developments in cascade, domino, and tandem reactions is the proficiency with which biological systems transform simple compounds into complex molecular frameworks. An ordinary vial under an inert atmosphere, aldehyde has been added to a stirred mixture of nucleophile. The products are obtained in good yields and excellent enantio- and dia-stereoselectivities. A sigmatropic rearrangement was performed, leading to a highly versatile building block for the total synthesis of a fusicoccane diterpenoid analogue.