5- chloro-2-pentanone

Chloro-2-nitropropane, 37, 25 5-Chloro-2-pentanone, 31, 74 a-CHLOROPHENYLACETIC ACID, 36, 3... 

Cyclization, 2-mercaptobenzoxazole from o-aminophenol, 30, 57 methyl cyclopropyl ketone from 5-chloro-2-pentanone, 31, 74... 

The higher rate of HC1 elimination of 4-chloro-l-phenyl-1-butanone with respect to 5-chloro-2-pentanone by a factor of 9.9 confirmed the participation of the C=0 group. The 7r-electron delocalization of the benzene ring increases the basicity and nucleophilicity of the carbonylic oxygen and led to greater stabilization of the transition state through assistance to the C—Cl bond cleavage in the transition state (equation 80). 

A. 5-Chloro-2-pentanone. A mixture of 450 ml. of concentrated hydrochloric acid, 525 ml. of water, and 384 g. (3 moles) of a-acetyl-7-butyrolactone (Note 1) and a boiling chip are placed in a 2-1. distilling flask fitted with a 90-cm. bulb-type condenser and a receiver immersed in an ice water bath (Note 2). Carbon dioxide is evolved immediately. Heating of the reaction mixture is begun at once, and the temperature is raised at such a rate that the reaction mixture does not foam into the condenser. In about 10 minutes the color changes from yellow to orange to black, the effervescence begins to subside, and distillation commences. The distillation is continued as rapidly as possible... 

B. Methyl cyclopropyl ketone. A 2-1. three-necked flask is fitted with a sweep-type stirrer made from K-in. iron rod (Note 6), a reflux condenser, and a 500-ml. dropping funnel. In the flask there is placed a solution consisting of 180 g. (4.5 moles) of sodium hydroxide pellets and 180 ml. of water. To this solution there is added over a period of 15-20 minutes 361.5 g. (342 ml., approximately 3 moles) of the crude 5-chloro-2-pentanone (Note 7). If the reaction mixture does not begin to boil during the addition, boiling is initiated by slight heating of the flask and is continued for 1 hour. Three hundred and seventy milliliters of water is then added slowly to the reaction mixture over a 20-minute period, and the mixture is heated under reflux for an additional hour. 

Corresponding runs beginning with 128 g. (1 mole) of a-acetyl-7-butyrolactone gave 107-112 g. (89-93%) of crude 5-chloro-2-pentanone. The checkers consistently obtained yields of 79-81% using U. S. Industrial Chemicals, Inc., lactone. 

Methyl cyclopropyl ketone has been prepared from ethyl aceto-acetate and ethylene bromide,6 and by the action of methyl-magnesium bromide on cyclopropyl cyanide.6-7 The procedure described for its preparation from 5-chloro-2-pentanone is similar to that of Zelinsky and Dengin.8 5-Chloro-2-pentanone has been prepared by a number of methods.9 The procedure given is essentially that of Boon 10 and of Forman.11 A similar procedure has been used for the preparation of the corresponding bromo-and iodoketones.10... 

C5H9Br 4-bromo-2-methyl-1-butene 20038-12-4 376.52 33 111 2 5068 C5H9CIO 5-chloro-2-pentanone 5891-21-4 396.53 34.038 2... 

The hexahydropyrroio[l,2-a]quinazolines 121 were prepared by Gatta and Landi Vittory by treating 2-aminobenzylamines (120) with 5-chloro-2-pentanone. 

Reaction of cis- and tra i-l,3-diphenyl-2,3-epoxy-4-bromo-l-butanones with triethyl phosphite at 120°C goes to completion to give diethyl cis- or tra i-l,3-diphenyl-4-oxo-2,3-epoxybutylphospho-nates as the only isolated products in high yields." Several preparations of 4-oxoaIkylphosphonates are based on the use of masked ketones. For example, the Michaelis-Arbuzov reaction of 5-chloro-2-pentanone ethylene ketal with triethyl phosphite followed by unmasking of the latent carbonyl group gives diethyl 4-oxopentylphosphonate in modest yield (38%)." ° ... 

Another example of the reduction of chloroketone is the reduction of 5-chloro-2-pentanone by TBADH as shown in Fig. 15-38 19. Using this biotransformation in the synthetic pathway, a naturally occurring heterocycle isolated from the glandular secretion of the dvet cat (Viverra civetta), was prepared. 

Figure 15-38. Reduction of 5-chloro-2-pentanone by TBADH for natural product synthesis1191.

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