Ethenylmagnesium bromide (1.5 equiv) forms a chelate with (−)-1-{(1S,2R,4R)-1-ethenyl-2-hydroxy-7,7-dimethylbicyclo[2.2.1]hept-2-yl} ethanone in THF and promotes its fast primary α-ketol rearrangement into 1-ethenyl-2-hydroxy-2,8,8-trimethylbicyclo[3.2.1]octan-3-one. The latter reacts with excess magnesium reagent (0.5 equiv) according to common 1,2-addition pattern at the carbonyl group and is simultaneously involved in the second α-ketol rearrangement which leads to 1-ethenyl-3-hydroxy-3,8,8-trimethylbicyclo[3.2.1]octan-2-one as thermodynamically more stable regioisomer.

Ethenylmagnesium bromide promotes the fast primary -ketol rearrangement of ()-1-(1S,2R,4R)-1-ethenyl-2-hydroxy-7,7-dimethylbicyclo[2.2.1]hept-2-y

Paper

Specificity of the reaction of (−)-1-{(1S,2R,4R)-1-ethenyl-2-hydroxy-7,7-dimethylbicyclo[2.2.1]hept-2-yl}xethanone with ethenylmagnesium bromide

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