Mercaptals startg

An ethereal soln. of LiAlH4 added dropwise with stirring to a soln. of 5-tosyl-D>arabinose diethyl mercaptal in ether-benzene, refluxed 8 hrs. with stirring, and allowed to stand overnight 5-deoxy-D-arabinose diethyl mercaptal (startg. m. f. 237). Y 56%. F. e. s. H. Zinner, K. Wessely, and H. Kristen, B. 92, 1618 (1959). 

A stirred soln. of startg. mercaptal in 9 1 methanol/water treated with (CF3C02)2lPh, and stirred at room temp, for 2 min 6-acetoxyhexanal. Y 85%. The method is mild, rapid, and leaves a variety of functional groups unaffected esters, nitriles, secondary amides, alcohols, halides, alkenes, alkynes, amines, and thioesters. F.e., also acetals in pure alcoholic media, s. G. Stork, K. Zhao, Tetrahedron Letters 30, 287-90 (1989). 

Carbohydrate derivatives. A soln. of D-mannose diethyl mercaptal in aq. 70%-ethanol treated portionwise with a slurry of Raney-Ni W 2 in ethanol, the composition of the mixture checked 15 min. after each addition, and the products isolated when the startg. m. has disappeared 4.31 g. crude 1-deoxy-1-ethylmercapto-D-mannitol and 0.98 g. 1-deoxy-D-mannitol. F. e. s. B. Lindberg and L. Norden, Acta Ghem. Scand. 15, 958 (1961). 

Equimolar amounts of the startg. cyclopropanone mercaptal and water dissolved at room temp, in trifluoroacetic acid, and allowed to react 5-10 hrs. cyclo-heptanone. Y 90%. F. e. s. D. Seebach, M. Braun, and N. DuPreez, Tetrah. Let. 1973, 3509. 

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