W-Bromoacetophenone

Aralkyl or Alkylarylthiazoles and 2,4,5-Trisubstituted Thiazoles (Tables II-5 and II-6). Alkylthioamides and their substituted derivatives have been condensed with w-bromoacetophenones (28) to... 

Ary] 2-amino-5-(p-aminophenyl)thia2oles of the general formula 116 were prepared by condensing phenylthiosemicarbazides (115) with either w-bromoacetophenone by refluxing in alcohol for 2 hr (Method A) or with acetophenones and iodine on a steam bath for 8 hr (Method B) Scheme 53 (517), with R = para Me, MeO, Cl, Br, I, NOj, NHj, Ph ortho Me, NOjl or meta Br, I, NO. Yields ranged from 55 to 90% from Method A and 40 to 70% from Method B. 

The addition of cyanogen to 3 4-diaminophenylarsinic acid leads to the production of a di-imino-dikydroquinoxcdine (I), and the addition of w-bromoacetophenone leads to a phenyl-dihydroquinoxaline (II). No method has been found which will decide the position of the phenyl group in the quinoxaline ring. ... 

A direct and simpler conversion of w-bromoacetophenone into phenylglyoxal is achieved by treatment with dimethyl sulfoxide at room temperature [1003], The reaction of a-bromo ketones with dimethyl sulfoxide can be carried out in anhydrous medium [1003], as well as in the presence of water [1001], The mechanism of the reaction in aqueous medium is more... 

Fry and coworkers [191] observed that electrolysis of w-bromoacetophenone at mercury in DMF containing TEABr affords acetophenone, whereas reduction of p-bromo-K-chlorobutyrophenone gives /-chlorobutyrophenone. 

Sato and Ohta (307) who reinvestigated the reaction of dithiocarbazic acids with chloroacetone and w-bromoacetophenone also described the 3.4-dihydro-2H-1,2,4-thiadiazine-2-thione structure to the products. These authors also describe the condensation of N-benzoyl dithiocarbazic acids (CCXV, Rj—CgHjCO with a-halo ketones which yields 4-benzoyl-3,4-dihydro-2H-t, 3,4-thiadiazine-2-thiones (CCXVIII, These products hydrolj ze in acid medium (with formation of benzoic acid) and simultaneously undergo a transformation to 3-amino-zl4-thiazoline-2-thiones. These facts support the remarks made earlier. 

The reaction between w-bromoacetophenone or its p-substituted derivatives and cyanourea is dependent on pH and gives either an imidazole or an oxazole derivative, depending on the conditions.113 Thus, equimolar amounts of w-bromoacetophenones and cyanourea in the presence of 2.5-3 M sodium acetate in ethanolic medium give 30-50% yield of the corresponding 2-amino-5-aryloxazole (47). The mechanism of the reaction is uncertain, but it is believed to proceed through the anion of cyanourea... 

This reaction is different from that of Gompper and Christmann104 inasmuch as the latter gives 2-amino-4-aryloxazole from the reaction of w-bromoacetophenones and urea. 

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