Haloacetaldehyde alkyl 2-cyclopentenyl acetal compound and a process for preparing the same, a process for preparing a (2-cyclopentenyl)acetate ester compound therefrom, and a process for preparing a (2-cyclopentenyl)acetic acid compound therefrom

A process for preparing a (2-cyclopentenyl)acetate ester compound of the following general formula (2):

• wherein R represents a linear or branched alkyl group having 1 to 4 carbon atoms, X1 to X7 are as selected in the general formula (1), respectively, the process comprising:
• halogenating an alkyl vinyl ether compound of the following general formula (4):
• wherein R represents a linear or branched alkyl group having 1 to 4 carbon atoms, with a halogenating agent to form a halide;
• and
• subjecting the halide to a substitution reaction with a 2-cyclopenten-1-ol compound of the following general formula (5):
• wherein X1 to X7 represent, independently of each other, a hydrogen atom or a methyl group, with the proviso that one to three among X1 to X7 represent a methyl group and the remaining represent a hydrogen atom,
• to form a haloacetaldehyde alkyl 2-cyclopentenyl acetal compound of the following general formula (1):
• wherein R represents a linear or branched alkyl group having 1 to 4 carbon atoms, X1 to X7 are as selected in the general formula (5), respectively, and Y represents a halogen atom;
• and
• subjecting the haloacetaldehyde alkyl 2-cyclopentenyl acetal compound (1) to a dehydrohalogenation reaction in the presence of a base, followed by a rearrangement reaction to form the (2-cyclopentenyl)acetate ester compound (2).

A haloacetaldehyde alkyl 2-cyclopentenyl acetal compound of the following general formula (1):

• wherein:
• R represents a linear or branched alkyl group having 1 to 4 carbon atoms;
• X1 to X7 represent, independently of each other, a hydrogen atom or a methyl group, with the proviso that one to three among X1 to X7 represent a methyl group and the remaining represent a hydrogen atom, with the proviso that when X1 represents a methyl group, one or two of X2 to X7 represent a methyl group, and with the proviso that when X1 and X2 are methyl and X3 to X7 are hydrogen, R is not ethyl;
• and
• Y represents a halogen atom.