| 摘要 |
The prepn. of 3-oxopentanoic acid alkyl esters of formula (I) comprises (a) reacting an a,b-unsatd. aldehyde of formula (II) with ketene CH2=C=O (III) to give a 4-alkenyl-2-oxetanone of formula (IV); (b) converting (IV) by treatment with an alkali alcoholate of formula nOR (V) followed by neutralisation via the corresp. alkali salt to give the 3-hydroxy-4-pentenoic acid alkyl ester of formula (VII); and (c) isomerising (VI) by treatment with a Rh, Pd or Pt catalyst in an inert solvent to give (I). R = opt. branched 1-4C alkyl; R1 = H or Me M = Li, Na or K. USE/ADVANTAGE - (I) are starting materials for the synthesis of a large number of acyclic, isocyclic and heterocyclic cpds. which are pharmaceuticals, plant protecting agents and dyestuffs. The process can give longer chain 3-oxocarboxylic acid esters, and ones which are f-branched, e.g, 4-methyl-3-oxopentanoic acid esters, using cheap starting materials and conditions which pose no problems (e.g, the need to use liq. ammonia is avoided).
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