Au/Pd Relay Catalytic Tandem Cyclization Reaction for the Diastereoselective Construction of Spirocyclic Furan-α-Imine Derivatives

We report a diastereoselective Au/Pd relay catalytic tandem cyclization reaction to access polysubstituted dearomatized 2-oxaspiro[4.4]nonane derivatives under mild conditions. The process generates a furan-derived azadiene from a readily available enynamide, followed by a [2 + 3] cycloaddition with the Pd-π-allyl dipole formed by ring opening of a vinylcyclopropane. The method constructs spiro[4.4]nonane skeletons with considerable flexibility, affording yields of 57–98% and diastereoselectivities of >20:1 dr across 24 examples. This approach extends the use of azadiene intermediates as 1,2-dipoles and provides an effective route to dearomatized spirocyclic furan-α-imine frameworks.