Process for producing 3-formylcyclopentanone derivatives

A process for producing a 3-formylcyclopentanone derivative having the formula ##STR12## which comprises:

• reacting a .beta.-dicarbonyl compound having the formula ##STR13## with an azide under basic conditions to produce an .alpha.-diazo-.beta.-dicarbonyl compound having the formula ##STR14## treating said product under conditions suitable for producing a carbene or carbenoid to produce a bicyclo hexane-2-one derivative having the formula:
• ##STR15## reacting said product with a mercaptan having the formula, R.sub.5 SH, in the presence of a base to produce a cyclopentanone derivative having the formula ##STR16## reacting said product with an alkylating agent having the formula RZ in the presence of a base to produce a cyclopentanone derivative having the formula ##STR17## decarboxylating said product to produce a cyclopentane sulfide derivative having the formula ##STR18## oxidizing said product to produce a cyclopentanone sulfoxide derivative having the formula ##STR19## reacting said product with an acid anhydride;
• and treating the obtained product with an acid or a base;
• wherein R.sub.4 is an alkyl or an alkoxy group;
• R.sub.5 is a hydrocarbon group having less than 10 carbon atoms;
• R is a C.sub.1-10 alkyl or C.sub.2-10 alkenyl group substituted by a lower alkoxycarbonyl group, X is a hydrogen atom, an alkoxy group, a tetrahydropyranyloxy group or a silyloxy group;
• and Z is a leaving anion.