Nucleophilic addition with Grignard reagents on cyclic N,O-acetals^a.

Entry	N,O-Acetals	R1	R2	R3	Time	2	Yield (%)	syn/antib
1	1a	Me	H	Allyl	10 min	2a	96	69/31
2	1a	Et	H	Allyl	10 min	2b	97	91/9
3	1a	i-Pr	H	Allyl	7 h	2c	88	100/0
4	1a	Cy	H	Allyl	18 h	2d	83	100/0
5	1a	Allyl	H	Allyl	10 min	2e	98	0/100
6	1a	Ph	H	Allyl	10 min	2f	98	100/0
7	1b	Me	Me	Allyl	10 min	2g	91	88/12
8	1b	Allyl	Me	Allyl	10 min	2h	90	0/100
9	1c	Me	Cl	Allyl	10 min	2i	92	67/33
10	1c	Allyl	Cl	Allyl	10 min	2j	91	0/100
11	1d	Me	H	Me	10 min	2k	92	68/32
12	1d	i-Pr	H	Me	5 min	2l	91	100/0
13	1e	Me	H	H	1 h	2m	80	91/9
14	1e	Allyl	H	H	10 min	2n	81	75/25

^aUnless indicated otherwise, the reaction was carried out on 1.0 mmol scale in DCM (10 mL).

^bDiastereoisomeric ratios were determined by ¹H NMR analysis of the mixture, see the ESI for details.