Organocascade Synthesis of Spiro[chroman‐3,2′‐indanedione] Scaffolds via [4+2] or [1+1+4] Cyclisation

Abstract

A simple and convenient protocol has been demonstrated for the construction of spiro[chroman‐3,2′‐indanedione] via Oxa‐Michael/Michael cascade reaction sequence using 2‐arylidene‐1,3‐indanedione and (E)‐2‐(2‐nitrovinyl)phenol. This [4+2] cyclisation protocol results in the generation of two stereocentres along with an all carbon quaternary centre in good to high chemical yields of upto 93 %. A triple cascade reaction approach was carried out for the construction of spiro[chroman‐3,2′‐indanedione] using [1+1+4] cyclisation protocol.

Synthesis of fully functionalised spiropyran pyrazolone skeletons via a formal [4 + 2] cascade process using β-nitro-styrene-derived MBH-alcohols

“…On the other hand, the utility of nitro-styrene-derived MBH alcohols as 1,4- bis -ambiphiles (α-C, δ-O) has been less extensively investigated. 20 In continuation of our efforts towards the synthesis of various spirocyclic systems, 21 herein we report the synthesis of spiropyrazolone tetrahydropyran scaffolds using β-nitro-styrene-derived MBH alcohols, resulting in the formation of the desired products with 4 to 5 contiguous chiral centers through [4 + 2] annulation (eqn (d), Scheme 1 ).…”

Diastereoselective synthesis of chroman bearing spirobenzofuranone scaffolds via oxa-Michael/1,6-conjugated addition of para-quinone methides with benzofuranone-type olefins

“…3,4 In particular, incorporating chroman into spiro-bridged and spiro-fused heterocyclic systems is appealing due to its fascinating molecular architecture and proven biological activity. 5 Among the existing methods, the [4 + m] cycloaddition of para -quinone methides ( p -QMs) is found to be an efficient pathway to access these valuable spirocyclic skeletons. 6 For instance, the Enders group synthesized functionalized chromans with an oxindole motif by the asymmetric organocatalytic domino oxa-Michael/1,6-addition reaction.…”