Ring transposition procedure

Application of the MVK annulation procedure to enamines of acyclic ketones and aldehydes gives cyclohexenones. If the aldehyde carbonyl group is attached to a ring, the procedure provides a valuable stereoselective method for the spiroannulation of cyclic ketones (Scheme 138). The use of l-methoxybut-3-en-2-one in place of MVK provides a means for subsequent 1,2-transposition of a ketone carbonyl function (Scheme 139). Condensation of 2,2,2-trifluoroethyi vinyl ketone with enamines gives 2-trifluoromethylcyclohexenones °. 

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