Control of Synthetic Reactions by the Use of Organo Boron Compounds

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6,8-Diphenyl-1-hydroxy-1,2,3,4-tetrahydro-2-oxa-1-boranaphthalene, which is expected to form boronate esters with hydroxyl compounds and to cover one face of the substrates to control the selectivities of the reaction, . was designed and synthesized For example, thi boron compound forms the boronate ester preferentially with the beta-anomer of 2-deoxyribose derivative. When this compound was added to tert-butyl 5-benzyl-2-deoxyribose, preferential esterification with the beta-anomer was observed. This boron compound is successfully employed for the stereoselective reduction of acyclic and cyclic beta-hydroxy detones. The boron compound and acyclic ketones were converted to the corresponding boronates by azeotropic removal of water, and the resulting boronates were treated in situ with reducing reagent to give syn 1,3-diol almost exclusively. Anti alpha-substituted beta-hydroxy ketones were also reduced to give anti, anti 1,3-diol stereoselectively. Furthermore, the reducton of 3-hydroxy-1-cyclopentanone gave a cis diol in high yield.Dicyanophenylmenthol derivative was synthesized from R-(+)-Pulegone in eight steps as a chiral sensitizer, . As a controlled experiment, phenylmenthyl crotonate was irradiated using high-pressure mercury lamp in the presence of diethy (trimethylsilylmethyl) amine in methanol-acetonitrile and in this case, photochemical aminomethylation did not proceed. However, under the same conditions, the chiral crotonate having a sensitizer part gave the corresponding gamma-aminomethyl ester diastereoselectively (conversion yield 58%, 40%d.e.). Based on this result, a novel substituent effect of the sensitizer was discovered.