Doctor of Philosophy
A novel enantiomerically pure, internally coordinated alkylchloroborane monomer was synthesized using commercially available materials. The applications of this unique chiral borane (11A) were explored. It was known that H. C. Brown had developed a chloro?derivative of his monoalkyl borane (IpcBCl(OR)) and was able to convert symmetrical epoxides into chlorohydrins with reasonable ee’s. For example, Brown obtained the chlorohydrin from cyclohexene oxide with a 35% ee. It was unlcear if this novel chiral chloroborane would generate chlorohydrins or simply alcohols since there is still a hydrogen present unlike Brown’s chloroborane. The application of the chiral chloroborane for reduction of ketones was also explored because boranes are known to readily reduce aldehydes and ketones to their corresponding alcohols. Dipinylchoroborane is well-known for an asymmetric reaction reducing ketones or aldehydes with good ee’s (84-98%). Lastly, The hydroboration of 1,4-dienes using a chloride/hydride exchange wherein only the intramolecular step creates a new chiral center was explored. Early results indicate this approach has three benefits: for R = methyl, (a) the process is regioselective, forming 1,4- diols in a 17:1 ratio; (b) the intramolecular process gives better asymmetric induction (84% ee). This approach should significantly augment the few existing routes to non-racemic 1,4- dioxygenated intermediates. Many pharmaceuticals require precise placement of functional groups, with most common of these groups being oxygen, therefore, having a method for effectively forming chiral 1,4-diols would be beneficial.
Dissertation or thesis originally submitted to ProQuest.
von Dollen, Breanna N., "ASYMMETRIC INTRAMOLECULAR HYDROBORATION VIA A UNIQUE CHIRAL CHLOROBORANE" (2023). Electronic Theses and Dissertations. 3302.