Table 3.

Acetylenylation of N,O-acetal TMS ethers.

Entry a	n	R	Yield b
1	1	H	30
2	1	SiMe3	29
3	1	Me	35
4	1	Ph	31
5	2	H	28
6	2	SiMe3	38
7	2	Me	89
8	2	Ph	88
9	3	H	84
10	3	SiMe3	36
11	3	Me	82
12	3	Ph	68
13	4	H	58
14	4	SiMe3	64
15	4	Me	80
16	4	Ph	81

^a All reactions were performed using 0.2 mmol of 2a–d in dry solvent (2 mL) by first adding the nucleophile at −78 °C followed by adding BF₃·OEt₂ and stirring for 1 h. The mixture was then slowly warmed to r.t. over 1 h before quenching with Et₃N. ^b Isolated yields.