The Cyclohexa‐2,5‐dienyl Group as a Placeholder for Hydrogen: Organocatalytic Michael Addition of an Acetaldehyde Surrogate.

An aldehyde with a cyclohexa‐2,5‐dienyl group in the α‐position is introduced as a storable surrogate of highly reactive acetaldehyde. The cyclohexa‐2,5‐dienyl unit is compatible with an enantioselective Michael addition to nitroalkenes promoted by a Hayashi–Jørgensen catalyst and can be removed by a boron Lewis acid mediated C−C bond cleavage. The robust two‐step sequence does not require a large excess of the aldehyde component that is typically needed when directly using acetaldehyde. [ABSTRACT FROM AUTHOR]