Table 3.

Tandem Isomerization–[4 + 2] Cycloadditions.

entry	propargyl amidesa	time [h]	cycloadducts	yield [%]b
1	30	24	14a	84
2		24		79c
3		24		42c,e
4		16		25d,e
5	32	14	19	63

^aUnless otherwise noted, all reactions were carried out in THF at concn = 0.10 M with 20 mol % of t-BuOK. For entries 1 and 5: Reaction temp = 65 °C; for entries 3 and 4: temp = 85 °C; and for entry 2: temp = 25 °C.

^bIsolated yields.

^cdr = ~3:1.

^ddr = ~2:1.

^eThe reaction was slower, and also observed was hydrolysis of the starting allenamide.