[20757-87-3]  · C5H7ClO  · 5-Chloro-1-penten-3-one  · (MW 118.56)

(reagent for the construction of fused ring systems and polyketones with 1,4- and 1,5-carbonyl relationships)

Physical Data: bp 25 °C/0.08 mmHg.

Solubility: sol most organic solvents.

Analysis of Reagent Purity: 1H NMR data are available.1

Preparative Method: not commercially available; prepared in a two-step sequence from b-chloropropionyl chloride and ethylene to give 1,5-dichloro-3-pentanone in 95% yield,2 which is then monodehydrochlorinated in 83% yield;3 earlier preparations4,5,6 of 1,5-dichloro-3-pentanone gave much lower yields.

Handling, Storage, and Precautions: use in a fume hood.


The reagent is used to generate a 2,6,10-triketone, which can be condensed to a tricyclic system1 by multiple intramolecular aldol condensations (eq 1). It is the synthetic equivalent of Divinyl Ketone; however, it allows sequential Michael addition of two different carbonyl compounds to produce an unsymmetrical 2,6,10-triketone, a procedure which is unsuccessful if used with divinyl ketone.

Diels-Alder Reaction.

The reagent undergoes a Diels-Alder reaction to yield b-chloro ketones, which can be dehydrohalogenated to the vinyl ketones. Thiazolium salt catalyzed additions of aldehydes to the vinyl ketones lead to 1,4-diketones, which can be further elaborated by repeated sequences of the same type to 1,4,7-triketones and 1,4,7,10-tetraketones (eq 2).3

1. Danishefsky, S.; Migdalof, B. H. JACS 1969, 91, 2806.
2. Owen, G. R.; Reese, C. B. JCS(C) 1970, 2401.
3. Stetter, H.; Jansen, B. CB 1985, 118, 4877.
4. Jones, N.; Taylor, H. T. JCS 1961, 1345.
5. Catch, J. R.; Elliott, D. F.; Hey, D. H.; Jones, E. R. H. JCS 1948, 278.
6. Baddeley, G.; Taylor, H. T.; Pickles, W. JCS 1953, 124.

Girts Kaugars

The Upjohn Company, Kalamazoo, MI, USA

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