Intramolecular Oxa-Michael Reactions of Aldols Generated from Enones and Isatins to Afford Spirooxindole Tetrahydropyrans

Abstract

Spirooxindole derivatives are found in bioactive natural products and are used in drug discovery and related research. Here, acid-catalyzed diastereoselective intramolecular oxa-Michael cyclization reactions of -hydroxyenones generated from enones and isatin derivatives that afford spirooxindole tetrahydropyrans are reported. The major diastereomers of the

Control of Chemical Reactions by Using Molecules that Buffer Non‐aqueous Solutions

“…[12,13,19,20] Under acidic conditions with TfOH, compound 18 was transformed to oxa-cyclization product 19. [18] The same reactionb ut with the addition of 1b led to the dimerizationo f18,r esulting in the formation of spirooxindole octahydropentalene derivative 28 (Scheme 4a). Ther elative stereochemistry of 28 was determined by X-ray crystal structural analysis.…”

“…Under acidic conditions, compound 18 wasr eadily converted to oxa- Michael cyclization product 19. [18] Neat conditions fort he reaction of 18 with furan using TfOH as catalystr esulted in the formation of ac omplex mixture containing more than six new spots on TLC analysis; none of them were 20 or 21.Incontrast, the reaction under the same neat conditions but in the presence of 1b afforded furan-added products 20 (keto form) and 21 (enol form;S cheme 3a). Similarly,T fOH-catalyzed reactions of b-hydroxyenone derivative 22 with furan in the presence of 1b afforded corresponding additionp roducts 23 and 24 (Scheme 3b), and the reactiono f14 under these conditions yielded 25 (Scheme 3c).…”

Synthesis of Functionalized Spirooxindole Polycycles: Use of Cyclic 1,3-Diones as Reactants or as Condition-Tuning Molecules

“…the intramolecular oxa-Michael reaction product 12 was formed (Scheme 4b). 5,6 Treatment of 12 with dione 2b in the presence of triflic acid did not alter 12, and no formation of 11 was detected (Scheme 4b). 5 As described in Section 2, when compounds 1 were treated with triflic acid in the presence of 1,3-cyclohexanedione (2a), products 3 were formed (Scheme 1a).…”