Table 2.

Synthesis of the cycloadducts 7a–7c by Knoevenagel condensation and HDA reaction in the reaction conditions A–D

Entry	Method	1	2	3	4	R1	R2	6	7	8	Reaction time/h	Yield/% of 7 a	Ratio of cis-7/ trans-7 b
1	A	1a	2d	3d	4a	C2H5	H	–	7a	8a	18	82	>100:1
2	B	1a	2d	3d	4a	C2H5	H	–	7a	8a	16	81	>100:1
3	C	1a	2d	–	4a	C2H5	H	–	7a	8a	15	80	>100:1
4	D	1a	2d	–	4a	C2H5	H	6a	7a	8a	8	82	>100:1
5	A	1a	2d	3d	4b	i-Bu	H	–	7b	8b	18	81	6.3:1
6	B	1a	2d	3d	4b	i-Bu	H	–	7b	8b	17	78	5.9:1
7	C	1a	2d	–	4b	i-Bu	H	–	7b	8b	15	77	6.5:1
8	D	1a	2d	–	4b	i-Bu	H	6b	7b	8b	8	76	8.1:1
9	A	1a	2d	3d	4c	CH3	CH3	–	7c	8c	24	78	5.3:1
10	B	1a	2d	3d	4c	CH3	CH3	–	7c	8c	20	75	5.5:1
11	C	1a	2d	–	4c	CH3	CH3	–	7c	8c	18	82	5.2:1
12	D	1a	2d	–	4c	CH3	CH3	6c	7c	8c	10	80	7.5:1

^aIsolated yields after column chromatography

^bRatio based on ¹H NMR (300 MHz) spectra of crude products