O-Vinyl Oximes for Formation of Carbon–Carbon and Carbon–Nitrogen Bonds, Pyridines from N-Vinyl Nitrones

The formation of new carbon–carbon and carbon–nitrogen bonds is extremely important in the synthesis of valuable organic compounds. Development of new methods to construct these bonds is necessary to access challenging structures and retain sensitive functional groups. The rearrangement of O-vinyl oximes ethers to form new carbon–carbon and carbon–nitrogen bonds has been exploited to access these structures. By a [3,3]-rearrangement with acetophenone-derived O-vinyl oxime ethers, 2,3,4-trisubstituted pyrroles are quickly accessible from simple starting materials. Alternatively a [1,3]-rearrangement of acetophenone-derived O-vinyl oximes can produce the 2,3,5-trisubstituted pyrroles. The [1,3]-rearrangement can be exploited further to give α-imino aldehydes from benzophenone-derived O-vinyl oxime ethers. Mechanistic experiments have been performed to understand the [1,3]-rearrangement of O-vinyl oxime ethers. Lastly, the formation of N-vinyl nitrones from vinyl boronic acids and α,β-unsaturated oximes and use in the synthesis of tri- and tetrasubstituted pyridines will be discussed.