Recyclable Polymeric π-Acid Catalyst Effective in Aqueous and Solvent-Free Inverse-Electron-Demand Aza-Diels-Alder Reactions

Abstract

A polymer-supported π-acid (poly-DCKA-1) was found to be a highly efficient and recyclable catalyst in two- and three-component inverse-electron-demand aza-Diels-Alder reactions at room temperature not only in water but also under solvent-free conditions.

polymer - π-acid catalyst - aza-Diels-Alder reaction - aqueous reaction - solvent-free reaction

References and Notes

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12

Masaki, Y.; Yamazaki, K.; Kawai, H.; Yamada, T.; Itoh, A.; Arai, Y.; Furukawa; H. Chem. Lett. submitted.

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17

Typical Procedure To a mixture of benzylideneaniline (453 mg, 2.5 mmol) and poly-DCKA-1 (189 mg, 0.5 mmol equiv) in H₂O (5.0 mL), was added 3,4-dihydro-4H-pyran (1.26 g, 15 mmol) at r.t., and the mixture was stirred for 24 h. EtOAc was added, the poly-DCKA-1 was removed by filtration, and the filtrate was extracted with EtOAc. The organic layer was washed with H₂O, dried over anhyd MgSO₄, and concen-trated in vacuo to give the crude product, which was purified by column chromatography on silica gel (hexane-EtOAc) to give pure diastereoisomers 9a (404 mg, 60%) and 9b (64 mg, 11%).

18

The catalyst poly-DCKA-1 was recovered by filtration from the reaction mixture followed by washing successively with H₂O and EtOAc, and drying in vacuo at r.t. for 4 h.