Table 3.

Cyclization of other adducts 4.

Entry	R1	R2		Yield [%]			Recovery of 4/%
				1	8	11
1	Me	OEt	c	8	39	0	0
2	Et	OMe	d	12	44	trace	0
3	iPr	OMe	e	24	36	9	0
4	Ph	OEt	f	56	9	17	0
5	Me	Me	b	0	21	0	17
6	Me	Ph	g	5	30a	0	7

^aTotal yield of two isomers 8g (14%) and 8g’ (R¹ = Ph, R² = Me, 16%).