Haloacetyl bromide

Reaction of ot-haloacetyl bromides with amides in the presence of strong acids... 

Bis (meta or para haloacetyl) benzenes (C1CH2C0)2C6H4 condensed with thiourea yield the corresponding meta or para bis(4-thiazolyl-2-amino)phenylene (573, 574), analogous to 36 with R=NH2-By refluxing in alcohol solution m- or p-2-thiazolylphenacyl bromide (37) with thiourea, compound 111, in which R = H, Ph, P-CIC6H4, and p-OjNC H, was obtained (569). 

Common hypervalent iodine(III) reagents, such as PhI(OAc)2 and PhI(OH)OTs, in the presence of bromide anions can be used for oxidative bromination of organic substrates. The oxidative halogenation of 1,4-dimethoxynaphthalene derivatives with (diacetoxyiodo)benzene and trimethylsilyl bromide or chio-ride affords the corresponding halogenated or haloacetylated products [91, 92]. For example, the treatment of 1,4-dimethoxynaphthalene (87) with PhI(OAc)2 and trimethylsilyl bromide affords 3-bromo-l,4-dimethoxynaphthalene (88) in quantitative yield (Scheme 3.33) [92]. 

As another example for one-step functionalization on polystyrene, the Friedel-Crafts acylation with haloacetyl and -propionyl bromide should be mentioned [68,69] (Fig. 19). The haloacylation is performed in nitrobenzene — which has the swelling power of toluene (see Table 3) — catalyzed by aluminum chloride at room temperature for 20 hours, yielding a capacity of 2.2 mequiv. of reactive sites/g of 2% cross-linked polystyrene [69]. The loading with bromoacetyl moieties of 0.05 mequiv./g found in another experiment [68] should be regarded as the lower limit of functionalization for practical use in the Merrifield synthesis. 

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