Control of Synthetic Reactions by the Use of Organo Boron Compounds

6，8-二苯基-1-羟基-1，2，3，4-四氢-2-氧杂-1-硼萘，预期其与羟基化合物形成硼酸酯并覆盖基底的一面以控制反应的选择性。例如，该硼化合物优先与2-脱氧核糖衍生物的β-端基异构体形成硼酸酯。当将该化合物加入到叔丁基5-苄基-2-脱氧核糖中时，观察到与β-端基异构体的优先酯化。这种硼化合物被成功地用于无环和环状β-羟基去酮的立体选择性还原。硼化合物和无环酮通过共沸脱水转化为相应的硼酸酯，所得硼酸酯用还原剂原位处理，几乎完全得到顺式1，3-二醇。反式α-取代的β-羟基酮也被还原，立体选择性地得到反式，反式1，3-二醇。以R-（+）-胡薄荷酮为原料，经八步反应合成了手性增感剂二氰基苯基薄荷醇衍生物。作为对照实验，在甲醇-乙腈中存在二乙基（三甲基甲硅烷基甲基）胺的情况下，使用高压汞灯照射巴豆酸苯薄荷酯，并且在这种情况下，不进行光化学氨甲基化。然而，在相同条件下，具有增敏剂部分的手性巴豆酸酯非对映选择性地产生相应的γ-氨基甲酯（转化率58%，d.e. 40%）。在此基础上，发现了敏化剂的一种新的取代基效应。

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.