Direct Alkene and Alkyne Borylation with Borenium Cations

含硼取代基的有机分子在药物发现、农用化学品和有机电子学的新分子合成中是广泛的中间体。这种普遍性源于它们在一系列官能团转化中的高效性，特别是涉及形成新C-X键（X =碳，氮，氧）的那些。这种功效与普通含硼化合物的稳定性和易于处理的结合解释了它们在合成化学家中的非凡流行。然而，将硼基团安装到有机分子上（称为硼基化）在历史上是通过低效的方法进行的，通常需要许多步骤、不期望的中间体、高反应性试剂和低温条件。新一代的硼基化方法在一定程度上改善了这种情况，但是这些方法需要卤化中间体、昂贵的过渡金属催化剂或者不能应用于某些重要的化合物家族。因此，开发用于不饱和有机分子的全新硼基化方法，在一个步骤中进行而不需要有毒的贵金属催化剂和低温条件的烯烃和炔将是非常有价值的。我们最近已经表明，环状有机分子（芳烃）可以使用三配位阳离子硼化合物（称为borenium阳离子）进行硼基化。该过程在环境温度下使用廉价且易于合成的硼鎓阳离子快速且高选择性地发生。重要的是，这个过程在没有贵金属的情况下一步完成，并且适用于其他现代方法难以解决的化合物类别。这一提议将通过使用硼阳离子来硼化广泛的炔和烯来扩展这一突破。这些无环化合物将以与芳烃类似的方式反应，从而允许C-H键直接转化为C-B键，容易地产生有价值的硼基化有机产物。通过对硼阳离子的细微修饰，我们还将依次向烯烃或炔烃添加硼和氢取代基（称为硼氢化）。经典的硼氢化途径涉及同时添加B和H，这导致某种产物几何形状。基于硼鎓阳离子的过程将是B和H取代基的逐步加成，使得能够获得互补加成几何结构。这将使重要的有机结构单元的廉价合成成为可能，而这些有机结构单元迄今为止是无法获得的或需要复杂的多步合成，通过持续使用廉价的试剂和硼化与制药和有机电子工业有关的烯烃和炔，将确保这项研究的商业可行性。Borenium阳离子与烯烃和炔烃的组合将提供一系列重要化合物的使用，这些化合物目前使用已建立的方法无法获得或在商业上不可行。

Organic molecules containing boron substituents are widespread intermediates in the synthesis of new molecules for drug discovery, agrochemicals and organic electronics. This ubiquity arises from their high efficacy in a range of functional group transformations, particularly those involving the formation of new C-X bonds (X = carbon, nitrogen, oxygen). The combination of this efficacy with the stability and ease of handling of common boron containing compounds explains their extraordinary popularity amongst synthetic chemists. However, the installation of a boron group onto an organic molecule (termed borylation) has historically proceeded by inefficient processes, often requiring numerous steps, undesirable intermediates, highly reactive reagents and cryogenic conditions. A new generation of borylation methodologies has improved this situation somewhat, but these approaches require either halogenated intermediates, expensive transition metal catalysts or cannot be applied to certain important families of compounds. Thus the development of fundamentally new borylation methodologies for unsaturated organic molecules, e.g., alkenes and alkynes that proceeds in one step without requiring toxic precious metal catalysts and cryogenic conditions would be extremely valuable.We have recently shown that cyclic organic molecules (arenes) can be borylated using three coordinate cationic boron compounds, termed borenium cations. This process takes place rapidly and with high selectivity at ambient temperature using inexpensive and readily synthesised borenium cations. Importantly this process occurs in one-step without precious metals and is applicable to classes of compounds other modern methodologies struggle with. This proposal will extend this breakthrough by using borenium cations to borylate a wide range of alkynes and alkenes. These acyclic compounds will react in an analogous manner to arenes allowing for the direct conversion of a C-H bond into a C-B bond facilely generating the valuable borylated organic product. By subtle modification of the borenium cation we will also sequentially add a boron and a hydrogen substituent to an alkene or alkyne (termed hydroboration). Classic hydroboration routes involved the simultaneous addition of B and H which results in a certain product geometry. The borenium cation based process will be a stepwise addition of B and H substituents, enabling a complementary addition geometry to be accessed. This will allow for the inexpensive synthesis of important organic building blocks that have hitherto been inaccessible or required complex multi-step syntheses.Throughout the commercial viability of this research will be ensured by the continual use of inexpensive reagents and by borylating alkenes and alkynes of relevance to the pharmaceutical and organoelectronic industries. The combination of borenium cation with alkenes and alkynes will provide access to a range of important compounds currently either inaccessible or not commercially viable using established methodologies.