Methyl-5-hexen-2-one

Department of Organic Chemistry, University of Madras, Madras-25, India. 

Submitted by Sandba Boatman and Charles R. Hauser 1 Checked by E. J. Corev and William E. Russey 

In a 1-1. round-bottomed flask equipped with a condenser are placed 78.0 g. (0.56 mole) of commercial anhydrous potassium arbonate, 45.0 g. (0.50 mole) of methallyl chloride (Note 1), 55.0 g. (0.55 mole) of 2,4-pentanedione (Note 1), and 300 ml. of anhydrous ethanol (Note 2). The mixture is refluxed on a steam bath for 16 hours. The condenser is replaced by a distilling head and condenser, and about 200 ml. of ethanol is distilled from the mixture (Note 3). Ice water (600 ml.) is added to dissolve the salts, and the mixture is extracted three times with ether. The 

Eastman Organic Chemicals practical grade methallyl chloride was distilled (b.p. 70-71°) Union Carbide Chemicals Co. 2,4-pentanedione was distilled (b.p. 134.5-135.5°). 

Commercial grade absolute ethanol was dried over Linde 3A molecular sieves. 

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Methyl-5-hexen-2-one has been prepared by alkylation of acetoacetic ester with methallyl chloride, followed by cleavage the overall yield in the two steps was 51%.2... 

Methylene 2 hexanone, 47, 87 5 Methyl 5 hexen 2-one, 47, 87 Methyl hvdrazine, 46, 85 Methyl isocyanide, 46, 7S Methy lmagnesium bromide, reaction with bis(10,9 borazarophenan-thryl) ether, 46, 67 reaction w ith thiophosphoryl chloride, 45,102... 

A. Methyl 3.6-dimethyl-3-hydroxy-6-heptenoate (Note 1). An oven-dried, threenecked, 500-mL, round-bottomed flask, is fitted with an efficient mechanical stirrer, a Claisen adapter bearing a reflux condenser with a nitrogen, inlet and rubber septum, and a thermometer. The flask is maintained under a static nitrogen pressure and charged with 5-methyl-5-hexen-2-one (24.20 g, 0.216 mol) (Note 2), trimethyl borate... 

The submitters used freshly distilled ketone prepared according to the Organic Syntheses procedure.4 5-Methyl-5-hexen-2-one is also available from Aldrich Chemical Company, Inc., and can be used as purchased. 

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