Process for the preparation of cyclic diketones

A process for the preparation of a compound of formula I

• 25
• wherein Q is an organic substituent so selected that the compound of formula I has a
• pK value of from 1 to 5;
• D is hydrogen or R3;
• E is hydrogen or R4;
• or
• D and E together are C2-C3alkylene, which may be mono- or poly-substituted by R6;
• A is C1-C2alkylene, which may be mono- or poly-substituted by R5;
• or, when D and E are other than C2-C3alkylene, A may additionally be carbonyl, oxygen or —NR7—;
• R1, R2, R3, R4, R5 and R6 are each independently of the others hydrogen, C1-C4alkyl, phenyl, C1-C4alkoxy, halogen, hydroxy, cyano, hydroxycarbonyl or C1-C4alkoxycarbonyl;
• and
• R7 is C1-C4alkyl, alkoxycarbonyl or C1-C4alkylcarbonyl, which comprises
• a) converting a compound of formula II
• 26
• wherein R1, R2, A, D and E are as defined for formula I, either in the presence of an amine base and a catalytic amount of a cyanide or in the presence of an alkali metal alcoholate or alkaline earth metal alcoholate, to a salt of formula III
• 27
• wherein R1, R2, A, D and E are as defined for formula I and M+ is an alkali metal ion, alkaline earth metal ion or ammonium ion,
• b) reacting that compound with a compound of formula IV
• X—C(O)—Q (IV)
• wherein X is a leaving group and Q is as defined for formula I, to yield a compound of formula V
• 28
• wherein R1, R2, A, D, E and Q are as defined for formula I, and
• c) converting that compound in the presence of catalytic amounts of cyanide ions and in the presence of a base to a compound of formula I.