Organocatalytic synthesis of substituted spirocyclohexane carbaldehydes via [4 + 2] annulation strategy between 2-arylideneindane-1,3-diones and glutaraldehyde

An organocatalytic domino reaction between 2-
arylideneindane-1,3-diones and glutaraldehyde has been
devised that gives functionalized spirocyclohexane carbaldehydes with an all-carbon quaternary center. The reaction
proceeds through a Michael/Aldol sequence in good-to-high
chemical yields and with high levels of stereoselectivity (up to
>95:5 dr and 99% ee) in the presence of the α,α-Ldiphenylprolinol trimethylsilyl ether 3 (20 mol %) and
DIPEA (20 mol %) in ether at 0 °C.