Cycloaddition Reaction of Ethyl Thioxoacetate and the Dienamine Derived from Pummerer's Ketone

Table 1

200 MHz ¹H N.M.R spectrum of the cycloadduct (21).

Protons	δ P.P.m.	Coupling constants (Hz)
7	6.93	ddq, j 8.2, 1.9 and 0.6
9	6.86	dP, j1,9 and 0.6
6	6.61	dm, j 8.2 and <0.4
4a	4.86	dd, j 4.0 and 0,7
OCH2CH3	4.21	q, j 7.2
de 11	4.11	dd, j 2.9 and1.3
4	3.35	d, j 4.0
1	2.92	qd, j 3.1 and 0.8
2β	2.57	dd, j 19.8 and 3.1
8-Me	2.26	S, with fine splitting
2α	1.97	ddd, j 19.8, 3.3 and 1.3
9b-CH3	1.63	S
OCH2CH3	1.28	t, j 7.2