Bogert-Cook synthesis

What is Bogert-Cook synthesis?

The Bogert-Cook synthesis, independently reported by Cook in 1932 and Bogert in 1933, is a two-step chemical process that condenses cyclohexanones with β-phenylethylmagnesium bromide through a Grignard Reaction. The resulting tertiary alcohol is then subjected to cyclodehydration with concentrated sulfuric acid H2SO4, which yields octahydrophenanthrene derivatives as well as a small amount of spiran.

Bogert-Cook synthesis
Bogert-Cook synthesis
Bogert-Cook synthesis
Bogert-Cook synthesis

It was initially believed that the mechanism of this reaction involved the initial dehydration of the intermediate carbinol, followed by cyclization of the olefin produced, but this has been found to be erroneous. Instead, it is now thought that the reaction may proceed through one of three possible intermediates, depending on the reaction conditions. When an alkyl or alkoxyl group is present at the meta position to the side chain in the phenyl ring, cyclization can lead to the formation of 5- or 7-substituted phenanthrene derivatives. The yield of spirane produced depends on the reactivity of the aromatic nucleus at the cyclization position, and the stereoisomer formed by cyclization with an unreactive aromatic nucleus is different from that obtained with a more reactive nucleus (such as phenyl).

The utilization of this reaction is not limited and can be applied broadly in the synthesis of hydrocarbons with multiple nuclei, which include a phenanthrene core.

References

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