Formation of halohydrins by halo amides

Br14CH2-14CH2OH is obtained in 90% yield from [14C]ethylene by use of A-bromo-acetamide.294 

Addition of HOX by means of A-halo amides is important for, inter alia, steroid syntheses. A 9(ll)-double bond adds OH at position 11 (11/S-OH) and Br at position 9 (9oc-Br). Solvents used are mixtures of water with acetone, dioxane, pyridine, or tert-butyl alcohol. 0.46N-perchloric acid has proved particularly suitable as acid since it reduces any tendency to formation of halohydrin esters.295 

80% of 9oc-bromohydrocortisone acetate (2) is obtained from 21 -acetoxy-17ot-hy droxy-4,9(1 l)-pregnadiene-3,20-dione (1) and A-bromoacetamide. The 9/3,11/3-oxide (3) obtainable therefrom is converted by HI at —20° or by HC1 or HF at 0° into the corresponding 9a-halo-hydrocortisone acetate (4) in good yield 295 For further details of addition of HOBr to steroids by A-bromoacetamide or A-bromosuccinimide see, inter alia, references.296-299 

Chlorourea can also be used to add HOC1 to C=C bonds.300 Chlorourea301 [m.p. 71° (dec.)] dissolves in ca. 5 parts of water it is best handled in solution explosions can occur during chlorination of urea (formation of nitrogen trichloride). 

Alkoxy bromides are obtained by treating a compound containing aC=C bond with A-bromoacetamide297 or another bromo amides (e.g., N,N-di-bromobenzenesulfonamide302,303), not in an aqueous medium but in anhydrous methanol or ethanol at 0-20° acyloxy bromides are obtained in glacial acetic acid.297,304 

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