A Catalyst‐Free Cycloaddition Reaction: Access to Spiro[chroman‐3,2’‐indene‐1’,3’‐dione] Scaffolds

Abstract

We have reported herein a catalyst‐free cycloaddition of ortho‐hydroxyphenyl‐substituted para‐quinone methides and 2‐arylideneindane‐1,3‐diones by which a series of chromans featuring a spiro indane‐1,3‐dione scaffolds were obtained in high yields without any additives. Importantly, both anti‐ and syn‐ diastereomers could be obtained as single diastereomers respectively. Moverover, the current methold provides a novel and convenient approach for the efficient incorporation of the two biologically important scaffolds (chroman and spiro indane‐1,3‐dione).

Synthesis of spiroindolenine-bearing chroman scaffolds based on a cyclization reaction of para-Quinone methides

“…11 The Li group reported a catalyst-free cycloaddition of p -QMs to 2-arylideneindane-1,3-diones to establish a series of chromans featuring a spiro indane-1,3-dione containing two biologically important scaffolds. 12 Recently, the Shi group developed metal-catalyzed oxa-[4+2] cyclizations of p -QMs with alkynyl benzyl alcohols to construct spiroacetal skeletons in high yields and good diastereoselectivities. 13 Despite these achievements, incorporating two pharmacophores containing spiroindoline and chroman scaffolds in these [4+ m ]-cycloaddition reactions by p -QMs has for all intents and purposes not been investigated so far to the best of our knowledge (Scheme 1).…”