Synthesis of Electron-Deficient 1,3,5-Triazines as Potential Azadienes for Inverse-Electron-Demand Diels–Alder Reactions

Abstract

Various 1,3,5-triazines with electron-withdrawing groups such as esters, thioesters, and amides were prepared. These triazines were synthesized using acyl chloride coupling methods from triazine 1a and various alcohols, ethanethiol, and amines. Lowest unoccupied molecular orbital (LUMO) energy and solubility for these 1,3,5-triazines were determined to assess their potential as azadienes in inverse-electron-demand Diels–Alder reactions (IDA). The thioester 8 showed less LUMO energy and more solubility than triazine 1, suggesting that it may be a better azadiene to study triazine IDA reactions.

Keywords:

• Inverse-electron-demand Diels–Alder reaction
• LUMO energies
• solubility
• 1,3,5-triazines

ACKNOWLEDGMENTS

This work was supported by grants (90713008 and 20802024) from the National Natural Science Foundation of China and Changchun Discovery Sciences, Ltd.

Notes

^a Reactions were conducted with 0.1 equiv of p-TsOH.

^b Yields are based on pure products isolated by chromatography.

^c NA denotes no reaction or that no desired product was isolated.

^a Reactions were conducted at room temperature.

^b Product isolated via crystallization.

^c NA denotes no reaction or that no desired product was isolated.

^a Yields were calculated for the three-step sequence and are based on pure products isolated via chromatography.

^a Solubility reported as mmol/ml; see the Experimental section for details.

^a LUMO energy was calculated using Spartan (B3LYP at 6-31G∗ level) and reported as eV.