3-Homoacyl coumarin: an all carbon 1,3-dipole for enantioselective concerted (3+2) cycloaddition

Abstract

A stereoselective concerted (3+2) cycloaddition is demonstrated from 3-homoacyl coumarins and alkylidene indandiones, resulting in fused spirocyclopentanes bearing four contiguous stereocenters.

[3+2] regioselective annulation reaction of 2-arylidene-1,3-indandiones towards synthesis of spirocyclopentenes: understanding the mechanism of γ-attackvs.α-attack using DFT studies

“…In recent years, a readily accessible material i.e. 2-arylidene-1,3-indandiones 24 has started gaining importance in the field of phosphine catalysed annulations. 25 A regioselective [4+2] 26 cyclisation between 2-arylidene-1,3-indandiones and γ-substituted allenoates was carried out explicitly by Huang and co-workers towards synthesis of spiro[4.5]dec-6-ene skeletons as δ-adduct (eqn (a), Scheme 1 ).…”

Enantioselective Construction of Spirooxindole‐Fused Cyclopenta[c]chromen‐4‐ones Bearing Five Contiguous Stereocenters via a Stepwise (3+2) Cycloaddition

“…We have found that 3-homoacylcoumarin as 1,3-dipole precursor proceeds the stepwise (3 + 2) cycloaddition reaction with unsymmetrical alkylidene oxindole electrophiles whereas a concerted (3 + 2) cycloaddition has been reported with symmetric indandione alkylidenes. [8] Further studies regarding the application of 3-homoacylcoumarin in other organocatalytic reactions are underway in our laboratory.…”

“…[7] In 2018, we reported a quinine-derived bifunctional thioureacatalyzed concerted (3 + 2) cycloaddition reaction for the highly stereoselective synthesis of five membered coumarin/indanedione-fused spirocyclopentanes bearing four contiguous stereocenters. [8] Inspired from our previous work, we were keen on developing a (3 + 2) cycloaddition reaction for spirooxindole scaffolds, utilizing 3-homoacylcoumarin and alkylidene oxindole electrophiles. The supposed cycloaddition reaction would lead to less explored hybrid scaffolds that comprise both the privileged moieties and also bear five contiguous stereocenters, including a quaternary spiro-stereocenter.…”

Asymmetric organocatalyzed synthesis of coumarin derivatives

“…A stereoselective [3 + 2] cycloaddition with indandione alkylidenes 103 and 3-homoacylcoumarin 70 as the 1,3-dipole precursor, to generate a series of coumarin/indandione-fused spirocyclopentanes 104 bearing four contiguous stereogenic centers, was described by Chen et al [ 68 ]. This transformation was catalyzed by a cinchona-thiourea derivative 105 furnishing the spiro compounds with good to high yield and enantioselectivity ( Scheme 33 ).…”