Multicomponent reaction (MCR) for constructing bis -spirocyclohexane skeletons using β-nitrostyrene derived MBH acetates, 1,3-indanedione and aldehydes via [1 + 1 + 1 + 3] annulation

AB 2 C type four component quadruple cascade reaction between MBH acetate, 1,3-indanedione and aldehydes via [1 + 1 + 1 + 3] annulation progressed through Knoevenagel/Michael/Michael/Michael sequence for the synthesis of b is-spirocyclohexane.