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-l-diphenylprolinol trimethylsilyl ether 3 (20 mol %) and DIPEA (20 mol %) in ether at 0 °C.