Dimethyl Sulfoxide (Alfa Aesar)
Oxalyl Chloride (Aldrich, freshly distilled)
Dichloromethane (Dried over Calcium Hydride)
Triethylamine (Distilled and stored over KOH)

Dimethyl sulfoxide (510 µL, 7.21 mmol, 4 equiv.) was added dropwise to a stirred solution of oxalyl chloride (310 µL, 3.60 mmol, 2 equiv) in dichloromethane (6.7 mL) at -78 °C. After stirring for 30 min, a solution of (R)-3-(benzyloxy)-2-methylpropan-1-ol (325 mg, 1.80 mmol, 1 equiv.) in dichloromethane (1.8 mL) was added via cannula. Stirring was continued for a further 1 h at -78 °C, then triethylamine (1.26 mL, 9.01 mmol, 5 equiv.) was added dropwise and the reaction mixture was allowed to warm to rt (ca. 1 h). 1.0 M aq. ammonium chloride (14 mL) was then added and the phases were separated. The organic phase was washed with 1.0 M aq. ammonium chloride (5 × 10 mL) and sat. brine (15 mL), then dried over sodium sulfate, filtered and concentrated in vacuo to afford (S)-3-(benzyloxy)-2-methylpropanal (314 mg, 98%) as a yellow oil.

The product can be used for further reactions without any purification. It is recommended to use freshly distilled oxalyl chloride for good yields.

1H (400 MHz, Chloroform) 1.15 (3H, d, J 7.0, CH3), 2.63 - 2.72 (1H, m), 3.66 (1H, dd, J 9.5, 5.5), 3.70 (1H, dd, J 9.5, 6.5), 4.54 (2H, s), 7.28-7.39 (5H, m), 9.74 (1H, d, J 1.5) 13C (101 MHz, Chloroform) 10.7, 46.8, 70.0, 73.3, 127.6, 127.7, 128.4, 137.8, 203.9.

Zampella, A.; Sorgente, M.; D'Auria, M. V., Tetrahedron: Asymmetry, 2002, 13, 681 - 685 doi:10.1016/S0957-4166(02)00178-7

Harried, S. S.; Lee, C. P.; Yang, G.;Lee, T. I. H.; Myles, D. C., J. Org. Chem., 2003, 68, 6646 - 6660 doi:10.1021/jo034521r
Omura, K. ; Sharma, A. K.; Swern, D., J. Org. Chem., 1976, 41, 975 - 962 doi:10.1021/jo00868a012