Process for the preparation of 2-substituted cyclopentanones

A process for the preparation of a 2-substituted cyclopentanone of the formula ##STR5## in which R.sup.1 represents straight-chain or branched C.sub.1 -C.sub.6 -alkyl, C.sub.3 -C.sub.7 -cycloalkyl or unsubstituted or halogen-substituted C.sub.7 -C.sub.12 -aralkyl,

• in which an adipic ester of the formula ##STR6## in which the two R.sup.2 are identical or different and each represent straight-chain or branched C.sub.1 -C.sub.10 -alkyl, C.sub.7 -C.sub.2 -aralkyl which are unsubstituted or substituted by up to 3 identical or different substituents selected from the group consisting of the halogens and the C.sub.1 -C.sub.6 -alkyl, C.sub.1 -C.sub.6 -alkoxy and nitro groups, or C.sub.6 -C.sub.10 -aryl which is unsubstituted or substituted by up to 3 identical or different substituents selected from the group consisting of the halogens and the C.sub.1 -C.sub.6 -alkyl, C.sub.1 -C.sub.6 -alkoxy and nitro groups,
• is reacted in the presence of an inert solvent with an alkoxide of the formula (III)
• M(OR.sup.3).sub.n (III),
• in which
• M represents an alkali metal or an alkaline earth metal,
• R.sup.3 represents C.sub.1 -C.sub.10 -alkyl, C.sub.3 -C.sub.10 -cycloalkyl or C.sub.7 -C.sub.2 -aralkyl and
• n, depending on the valency of M, represents 1 or 2,
• a salt of the cyclopentanone-2-carboxylic ester of the formula (IV) is thus obtained ##STR7## in which R.sup.2 has the meaning given under formula (II), and
• M represents one equivalent of an alkali metal or alkaline earth metal,
• this, without isolation, is alkylated with an alkylating agent of the formula (V),
• R.sup.1 --X (V),
• in which
• R.sup.1 has the meaning given under formula (I) and
• X represents halogen, C.sub.1 -C.sub.6 -alkylsulphonate, or C.sub.6 -C.sub.10 -arylsulphonate which are unsubstituted or substituted by up to two C.sub.1 -C.sub.4 -alkyl groups,
• a 2-R.sup.1 -cyclopentanone-2-carboxylic ester of the formula (VI) is thus obtained ##STR8## in which R.sup.2 has the meaning given under formula (II) and
• R.sup.1 has the meaning given under formula (I),
• and this, without isolation, is hydrolysed and decarboxylated by treating it with an acid and heating to give I in an overall yield of 80% or higher.