PREPARATION OF 2,2-DIMETHYL- OR 2,2,3-TRIMETHYL-6-METHYLENE- CYCLOHEXYLACETALDEHYDE

PURPOSE:To prepare the titled compound useful as a synthetic intermediate of gamma-irone, etc., in one stp and high yield by reacting 3,3-dimethyl-1-cyclohexenylmethanol, etc. with an alkyl vinyl ether using pivalic acid as a catalyst. CONSTITUTION:The objective compound of formula I can be prepared easily, in a yield of as high as >=90%, by contacting and reacting (A) 3,3-dimethyl- or 3,3,4- trimethyl-1-cyclohexeneylmethanol of formula 3 (R is H or CH3) with (B) an alkyl vinyl ether of formula 2 (R is H or lower alkyl) in an organic solvent such as toluene or in the absence of solvent, preferably in an inert gas atmosphere preferably N2 gas, etc., in the presence of pivalic acid catalyst at 50- 300 deg.C for 0.5-10hr. USE:Synthetic intermediate of gamma-irone, gamma-dihydroirone, gamma-dihydroionone, etc. useful as perfumery.