Table 1.

Conditions for catalytically generation of enolate equivalents from cinnamaldehyde for hetero-Diels–Alder reactions^*

Entry	Conditions	Base	Ratio 3∶4†
1	0.1 M THF, RT	25% DBU	1∶1
2	0.1 M EtOH, RT	25% DBU	No annulation products
3	0.1 M DCE, RT	25% DBU	1∶1
	0.1 M Tol, RT	25% DBU	1∶5
8		25% DIPEA	1∶0 (side products observed)‡
9		25% DMAP	1∶0
10		1 equivalent DBU	0∶1
		1.5 equivalent NEt3	1∶5
11	0.1 M Tol, 40 °C	25% DBU	1∶10
12	0.1 M CH2Cl2, 40 °C	15% DMAP	1∶0 (10∶1 d.r., 99% ee)
13		15% NMM	1∶0 (> 20∶1 d.r., 99% ee)

^*Reaction time: 18–24 h. DBU, 1,8-diazabicyclo[5.4.0]undec-7-ene; DMAP, N,N-4-dimethylaminopyridine; NMM, N-methylmorpholine; DIPEA. diisopropylethylamine RT, room temperature; d.r., diastereomeric ratio; ee, enantiomeric excess.

^†Product ratios determined by ¹H NMR of unpurified reaction mixtures. Minor cyclopentane-derived isomers also observed, see refs. 14 and 15 for details.

^‡Side products include substrate decomposition or unidentified materials.