Enantioselective Functionalizations of alpha-, beta-Unsaturated Carboxylic Acids using Chiral Boronic Acids
Final Report Abstract
First, the functionalization of α,β-unsaturated carboxylic acids was investigated. Initial experiments showed that the direct functionalization under various reaction conditions were not as facile as expected. In a typical reaction setup, comprising a transition-metal catalyst such as Mn(dpm)3, only stating material could be recovered. After extensive experimentation and variation of reaction conditions, it was found that a selective β C-H activation could be performed, allowing the formation of alkynylated unsaturated carboxylic acids. However, yields were low and only improvable upon increase of catalyst amount. Thus, the focus was turned towards the functionalization of other unsaturated systems. Unsaturated hydrazones proved to be interesting starting materials, which, after treatment with a cobalt or manganese catalyst under oxygen or air, could be transformed to various functionalized pyrazolines. Following up on these results, it was also possible to establish a protocol for the functionalization of unsaturated amides.
