Table 2.

Scope of aldehyde 2 ^a.

Entry	2,R2	4	Yield b (%)	dr c
1	2a,Ph	4a	85	88:12
2	2b,4-F-Ph	4b	80	81:19
3	2c,3-F-Ph	4c	70	62:38
4	2d,2-F-Ph	4d	90	92:8
5	2e,4-Cl-Ph	4e	79	81:19
6	2f,3-Cl-Ph	4f	71	76:24
7	2g,2-Cl-Ph	4g	83	81:19
8	2h,3,4-diCl-Ph	4h	85	86:14
9	2i,4-Br-Ph	4i	81	>95:5
10	2j,3-Br-Ph	4j	65	67:33
11	2k,2-Br-Ph	4k	90	93:7
12	2l,4-NO2-Ph	4l	85	>95:5
13	2m,3-NO2-Ph	4m	83	>95:5
14	2n,2-NO2-Ph	4n	86	94:6
15	2o,4-Me-Ph	4o	78	82:18
16	2p,3-Me-Ph	4p	71	75:25
17	2q,2-Me-Ph	4q	80	77:23
18	2r,4-OMe-Ph	4r	84	83:17
19	2s,3-OMe-Ph	4s	76	80:20
20	2t,2-naphthyl	4t	93	94:6
21	2u,2-furyl	4u	70	94:6
22	2v,2-thienyl	4v	79	93:7
23	2w,Benzyl	4w	76	77:23
24	2x,tBu	4x	72	72:28

^a All reactions were carried out with 1a (0.2mmol), 2 (0.2 mmol), 3a (0.22 mmol), TEA (0.2 mmol) in CH₂Cl₂ (2.0 mL) at reflux for 24 h. ^b Isolated yield. ^c Determined by ¹H-NMR analysis of the crude reaction mixture.