Synthesis of 3-(Phosphorylmethyl)cycloalkenones by Forced Conjugate Addition of α-Phosphonate Carbanions to Cyclic Enones

Abstract

Cycloalkenones were found to react with α-lithiated diethyl (phenylselanyl)methylphosphonate preferentially or exclusively at the carbonyl group giving 1,2-adducts. When complexes of cycloalkenones with aluminum tris(2,6-diphenylphenoxide) were used for this reaction, regioselective 1,4-addition was observed. Upon oxidation the thus-formed 1,4-adducts gave the corresponding 3-(phosphorylmethyl)cycloalk-2-enones. An alternative approach to the latter compounds involved 1,4-addition of diethyl lithiomethylphosphonate to 2-sulfinylcycloalk-2-enones followed by sulfoxide elimination.

Key words

conjugate addition - cycloalkenones - α-phosphonate carbanions - 3-phosphorylcycloalk-2-enones

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17

The starting cyclohexenyl sulfoxide was prepared by oxidation of the corresponding sulfide according to ref. 16. However, our product was crystalline and not an oil as reported. For full spectroscopic and analytical data, see the experimental part.