[3 + 2] Cycloaddition of para-Quinone Methides with Nitrile Imines: Approach to Spiro-pyrazoline-cyclohexadienones

J Org Chem. 2019 Jun 7;84(11):6719-6728. doi: 10.1021/acs.joc.9b00434. Epub 2019 May 9.

Abstract

[3 + 2] cycloaddition of para-quinone methides with nitrile imines under mild conditions has been achieved. The corresponding spiro-pyrazoline-cyclohexadienone products were constructed in good to excellent yields (up to 97% yield) with high regioselectivity. This straightforward protocol exhibits good functional group tolerance and scalability and provides the spiro-pyrazoline-cyclohexadienones.