Aza Diels–Alder reactions of sulfinimines with the Rawal diene

The aza Diels–Alder reaction of optically active sulfinimines with the Rawal diene leads to enantiomerically enriched dihydropyridones with ees up to 90%. The reaction was catalyzed by TMSOTf. The best results were obtained using 10-isobornylsulfinimines. Removal of the sulfinyl auxiliary occurred during workup of the reaction mixture. The reaction most likely proceeds via a stepwise mechanism. The addition of lithium 4-N,N′-dimethylamino-1,3-buten-2-olate to sulfinimines, followed by hydrolysis, gave dihydropyridones in lower yields and with opposite stereochemistry.

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(2S)-2,3-Dihydro-2-phenyl-4-(1H)-pyridinoneC11H11NOEe = 60%[α]D = +195.3 (c 2.51, EtOH)

(2S)-2-(3-Chlorophenyl)-2,3-dihydro-4-(1H)-pyridinoneC11H10ClNOEe = 68%[α]D = +104.9 (c 2.14, CHCl3)

(2S)-2,3-Dihydro-2-(2-furyl)-4-(1H)-pyridinoneC9H9NOEe = 69%[α]D = +430.1 (c 0.565, CHCl3)