Highly syn-diastereoselective Michael addition of enolizable ketones to 3-(diethoxyphosphoryl)coumarin

A new approach to 3-(diethoxyphosphoryl)-4-(2-oxoalkyl)-3,4-dihydrocoumarins by base promoted conjugate addition of enolizable ketones to 3-(diethoxyphosphoryl)coumarin is described. The resulting products were transformed into the corresponding α-methylene-δ-lactones. A transition state model rationalizing stereochemical outcome of the reaction is proposed.

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