J. Org. C h e m . 1985,50, 1751-1752 Selective Benzoylation of Diols with 1-(Benzoyloxy )benzotriazole
Table I. Selective Benzoylation of Diols with 1-(Benzoy1oxy)benzotriazolein CHaCla at Room Temperature product (isolated yield, %) secondprimary ary diol time, h benzoate benzoate dibenzoate
Sunggak Kim,* Heung Chang, and Wan Joo Kim Department of Chemistry, Division of Chemistry, Korea Advanced Institute of Science and Technology, Seoul 131, Korea Received October 17, 1984
Selective benzoylation of diols is one of the most useful reactions in the selective protection of hydroxy groups in organic synthesis. A number of methods have been developed for the selective benzoylation of diols involving various reagents such as benzoyl cyanide,' benzoylimidazole,2 and benzoyltetra~ole.~?~ In general, regioselectivity in benzoylation of diols with reported methods is not always great. We have found that the use of 1-(benzoy1oxy)benzotriazoles is very effective in the selective benzoylation of diols under mild conditions. 1-(Benzoy1oxy)benzotriazole was conveniently prepared in 85% yield by the reaction of benzoyl chloride with equimolar amounts of 1hydroxybenzotriazole and triethylamine in methylene chloride a t room temperature for 20 min. First, we have studied selective benzoylation of simple diols having primary and secondary hydroxy groups such as 1,2-propanediol, phenylethanediol, and 1,3-butanediol. Reaction of 1,2-propanediol with equimolar amounts of 1-(benzoy1oxy)benzotriazoleand triethylamine in methylene chloride at room temperature in 24 h gave 89% of the monobenzoate along with 4% of the dibenzoate. The monobenzoate turned out to be a 92:8 mixture of the primary benzoate and the secondary benzoate, which was determined by NMR analysis. Similar results were obtained with phenylethanediol as shown in Table I. Better selectivity was observed in the benzoylation of 1,3-diols. Reaction of 1,3-butanediol with equimolar amounts of the reagent and triethylamine at room temperature in 24 h gave 93% of the primary monobenzoate along with a small amount of the dibenzoate, whereas benzoylation of 2ethyl- 1,3-hexanediol gave almost exclusively the primary monobenzoate under the same conditions. In view of the great importance of the selective protection of hydroxy groups in carbohydrate chemistry:?' we have studied selective benzoylation with several carbohydrate derivatives. Reaction of methyl 4,6-0-benzylidenea-D-glucopyranoside with equimolar amounts of 1-(benzoy1oxy)benzotriazole and triethylamine in methylene chloride at room temperature for 5 h afforded a 90:4 mixture of the 2-0-benzoate and the 3-0-benzoate along (1) (a) Holy, A,; Soucek, M. Tetrahedron Lett. 1971,185. (b) Abbas, S. A.; Haines, A. H. Carbohydr. Res. 1975,39,358. (2)(a) Staab, H.A.; Mannschreck, A. Chem. Ber. 1962,95,1284.(b) Cramer, R.; Saenger, W.; Scheit, K. H.; Tennigkeit, J. Liebigs Ann. Chem. 1964,670,156. (c) Carey, F. A.; Hodgson, K. 0. Carbohydr. Res. 1970, 12,463. (d) Holder, N. L.; Fraser-Reid,B. Synthesis 1972,83. (3)Stawinski, J.; Hozumi, T.; Narang, S. A. J. Chem. SOC.,Chem. Commun. 1976,243. Kimura, J.; Iiizumi, K.; Yanagida, N. Bull. Chem. (4)(a) Mitsunob, 0.; Soc. Jpn. 1976,49,510.(b) Sekine, M.; Kume, A.; Hata, T. Tetrahedron Lett. i981,22,3617. (5)(a) Itoh, M.; Hagiwara, D.; Notani, J. Synthesis 1975,456. (b) Ueda. M.: Oikawa. H.: Teshroai, T. Ibid. 1983.908. ( 6 ) For an exceuent'review,&: Haines, A. H.Adu. Carbohydr. Chem. Biochem. 1976,33,11. (7)(a) Jeanloz, R. W.; Jeanloz,D. A. J.Am. Chem. SOC.1957,79,2579. (b) Jeanloz, R. W.; Jeanloz, D. A. Zbid. 1958,80,5692. (c) Williams, J. M.; Richardson, A. C. Tetrahedron 1967,23,1369. (d) Collins, P.M.; Gardiner, D.; Kumar, S.; Overend, W. G. J. Chem. Soc., Perkin Trans. 1 1972,2596.(e) Hanig, H.; Weidmann, H. Carbohydr. Res. 1975,39,374. (0Kondo, Y. Agric. B i d . Chem. 1977,41,2089. (g) Szeja, W.Synthesis 1979.821.
0022-3263/85/1950-1751$01.50/0
1751
CH3CHCHZ
/ I
24
92"
24
(83)
(9)
(5)
24
(93)
0
(3)
24
(95)
0
(
