ASYMMETRIC REDUCTIONS VIA TRIALKYLBORANES

手性在有机化学和生物有机化学中起着核心作用。 因此 光学活性化合物的合成是一项重要的奋进。 我们 已经发现某些B-烷基-9-硼双环[3.3.1]壬烷（9-BBN） 醛和炔基酮。 的 衍生自α-蒎烯和9-BBN的试剂诱导高度的 光学活性转化为醇产物。 例如 将苯偶姻-α-d和4-甲基-1-戊炔-3-酮还原为 相应的醇具有基本上完全的不对称诱导。 机理研究表明，这些反应是通过 六中心循环过程，而不是脱硼还原 过程 对于其他酮，如苯乙酮， 脱硼还原工艺变得重要。 通过运行 在高压下反应，可以完全抑制脱硼 并且可以有效地减少多种酮。 已经发现 手性酮可以在反Cram意义上被还原， 二烷基硼烷。 将探讨这些削减的范围。 一 硼氢化物试剂，其提供高达80% e.e.的不对称诱导。 开发了 将测试该试剂的新类似物， 机械研究开始。 光学活性胺的合成， 氨基醇和氨基酸通过亚胺的不对称还原，或 二烯与亚胺和取代酮的环化缩合，或 将探索醛。 [2，3]Wittig的立体化学 重排已被阐明。 反应机理研究 将开始解释观察到的立体选择性的差异 从E和Z起始材料。 此次重组的范围将是 探讨了 光学活性叔醇的合成 烷氧基醛的环缩合和通过不对称加成到 将研究炔丙基酮。

Chirality plays a central role in organic and bioorganic chemistry. Hence the synthesis of optically-active compounds is an important endeavor. We have found certain B-alkyl-9-borabiocyclo [3.3.1]nonanes(9-BBN) reduce aldehydes and alkynyl ketones under remarkably mild conditions. The reagent derived from Alpha-pinene and 9-BBN induces a high degree of optical activity into the alcohol product. For example benzaldehyde-Alpha-d and 4-methyl-1-pentyne-3-one are reduced to the corresponding alcohols with essentially complete asymmetric induction. Mechanistic investigations have shown that these reactions proceed via a six-centered cyclic process rather than a dehydroboration-reduction process. For other ketones, such as acetophenone, the dehydroboration-reduction process becomes important. By running the reaction at high pressure, the dehydroboration may be completely suppressed and a variety of ketones may be effectively reduced. It has been found that chiral ketones may be reduced in ananti-Cram sense with dialkylboranes. The scope of these reductions will be explored. A borohydride reagent which provides asymmetric inductions of up to 80% e.e. has been developed. New analogs of this reagent will be tested and mechanistic studies initiated. The synthesis of optically-active amines, amino alcohols and amino acids via the asymmetric reduction of imines or the cyclocondensation of dienes with imines and substituted ketones or aldehydes will be explored. The stereochemistry of [2,3]Wittig rearrangements has been elucidated. Mechanistic studies on this reaction will be initiated to explain differences in stereoselectivities observed from E and Z starting materials. The scope of this rearrangement will be explored. The synthesis of optically-active tertiary alcohols by cyclocondensations of alkoyx aldehydes and by asymmetric additions to propargyl ketones will be investigates.