Table 1.

Equilibration of acetal 23 to aldehyde 24

entrya	additiveb	23/32: 24c
1	—	66 : 34
2	—d	39 : 61
3	CuCl2	75 : 25
4	ZnCl2	41 : 59
5	Cu(OTf)2	36 : 64
6	Zn(OTf)2	30 : 70
7	3 Å MS	32 : 68
8	4 Å MS	29 : 71
9	4 Å MS/Zn(OTf)2	27 : 73
10	4 Å MS/Cu(OTf)2	28 : 72

^aEach entry started from pure acetal 23.

^bLewis acids were used in 20 mol %; molecular sieves were used in 0.5 g/mmol.

^cRatio determined by ¹H NMR analysis of crude reaction filtrate after 20–24 h.

^dAt 50 °C.