Investigation of the Cycloaddition Reactions of Some New Azophosphonates and Azobis(phosphonates): A New Manifestation of the Staudinger Synthesis
Newly synthesized azo-compounds, with one or two pendant phosphonate groups, have recently been shown to react easily with conjugated dienes, such as 2,3-dimethylbutadiene or cyclopentadiene. In both cases, the ensuing [4+2] cycloaddition reactions have led to the preparation, isolation, and full characterization of a series of products. However, there is no clear evidence in chemical literature on [2+2] cycloaddition reactions with an azo-component. These [2+2] reactions are rare in principle, and have been typically conducted with an alkene and a ketene component. This study investigated the question as to whether azo-compounds can participate in such reactions, in place of the alkene component. Investigation focused on diphenylketene, which was reacted with several azobis(phosphonates) or azophosphonates, at ambient temperature. The 1H-, 13C- and 31P-NMR spectroscopic results confirmed that a ring structure was formed, but the data suggested that instead of a [2+2] cycloaddition, resulting in a four-membered ring, a six-membered ring formed, the product of a formal [2+2+2] cycloaddition. The Staudinger synthesis, used for the preparation of β-lactam rings, provides a possible explanation for the mechanism of formation of the six-membered ring.
Vladimir A Benin
Primary Advisor's Department
Stander Symposium poster
"Investigation of the Cycloaddition Reactions of Some New Azophosphonates and Azobis(phosphonates): A New Manifestation of the Staudinger Synthesis" (2019). Stander Symposium Posters. 1541.