Decane-1,2-diol (as received),
benzoyl chloride (as received),
triethylamine (distilled from CaH₂),
toluene,
petroleum ether (40-60), (distilled)
ethyl acetate (as received)

To a mixture of decane-1,2-diol (0.174 g; 1 mmol) and triethylamine (0.505 g; 5 mmol) in toluene (30 cm³) was added benzoyl chloride (0.705 g; 5 mmol). The mixture was heated for 7 minutes in a domestic microwave oven (Sharp, 800 W, 2450 MHz) that had been adapted to fit a reflux condenser, (which was on). Alternatively, the mixture was lowered into an oilbath preheated to 140 ^oC. (Seven minutes was timed from when the internal temperature reached 109 ^oC.) The mixture was allowed to cool, during which time a solid precipitated (triethylamine hydrochloride). The mixture was filtered, then the solvent removed at reduced pressure with minimal heating (no more than 40 ^oC; a reasonable vacuum is required for this, i.e. water pump or house vacuum is not sufficient. We used a 'Divac' 2.2L capacity.) The concentrated product was washed through a silica plug using petrol ether, until all excess benzoyl chloride was removed. The product, 1-benzoyloxy-2-hydroxydecane, could be obtained using ethyl acetate. Further purification, if required, necessitated a larger column (isolated yield after second column chromatography 0.250 g; 90%).

The microwave method of heating gave complete selectivity. No other product could be observed in the crude nmr. When the oilbath method was employed a small amount of 1,2-bis(benzoyloxy)decane (5-9%) was formed due to the longer actual heating time. The purification technique is essential. The product must be washed through the silica as quickly as possible with petrol, otherwise benzoic acid is formed, and this contaminates the products. If any ethyl acetate is used while benzoyl chloride is still present, then the product is contaminated with ethyl benzoate, which proved very difficult to remove. The procedure was equally successful for all diols tried which contained both a primary and secondary hydroxyl groups: 1,2- and 1,3- butanediol, and 1,4-pentanediol. The same reaction was equally selective in acetonitrile after just 30 seconds, but the triethylamine hydrochloride co-product was soluble in this solvent, so could not be filtered. Unfortunately, the reaction could not be applied to sugars due to solubility problems.

m.p. 39-40 ^oC. ¹H nmr, CDCl₃: 0.88 (3H, m), 1.0-1.5 (12H, m), 2.15 (1H, s), 3.86-4.04 (1H, m), 4.23 (1H, dd, J₁ = 7.2 Hz, J₂ = 11.5 Hz), 4.40 (1H, dd, J₁ = 7.2 Hz, J₂ = 11.5 Hz), 7.40-7.60 (3H, m), 8.02-8.10 (2H, m)

S. Caddick, A. J. McCarroll, D. A. Sandham, Tetrahedron, 2001, 57, 6305.

P. J. Kocienski, Protecting Groups; Springer: New York, 1994.