Acetyl hypobromite

Bromination can also be carried out using solutions of acetyl hypobromite or trifluoroacetyl hypobromite. Acetyl hypobromite is considered to be the active halogen-ating species in solutions of hypobromous acid in acetic acid ... 

Acetyl hypobromite, 0729 Acetyl hypofluorite, 0751 Caesium fluoroxysulfate, 4256 Chlorodifluoroacetyl hypochlorite, 0603 Difluoroacetyl hypochlorite, 0653 Fluorine fluorosulfate, 4324 Heptafluorobutyryl hypochlorite, 1352 Heptafluorobutyryl hypofluorite, 1369 Hexafluoroglutaryl dihypochlorite, 1806 Pentafluoropropionyl hypochlorite, 1034 Pentafluoropropionyl hypofluorite, 1056 Propionyl hypobromite, 1154 Rubidium fluoroxysulfate, 4309 Trifluoroacetyl hypochlorite, 0594 Trifluoroacetyl hypofluorite, 0633... 

Acetylamino-l-oxo-2,2,6,6-tetramethylpiperidinium perchlorate, 3406b Acetyl azide, 0767 Acetyl bromide, 0724 Acetyl cyclohexanesulfonyl peroxide, 3028 Acetyldimethylarsine, 1623 Acetylenebis(triethyllead), 3665 Acetylenebis(triethyltin), 3666 Acetylenedicarboxylic acid, 1401 Acetyl hypobromite, 0725 Acetyl hypofluorite, 0748... 

Acetyl hypobromite, 0725 Acetyl hypofluorite, 0748 Caesium fluoroxysulfate, 4250 Chlorodifluoroacetyl hypochlorite, 0600 Difluoroacetyl hypochlorite, 0649 Fluorine fluorosulfate, 4318 Heptafluorobutyryl hypochlorite, 1348 Heptafluorobutyryl hypofluorite, 1365 Hexafluoroglutaryl dihypochlorite, 1800 Pentafluoropropionyl hypochlorite, 1030 Pentafluoropropionyl hypofluorite, 1053 Propionyl hypobromite, 1150 Rubidium fluoroxysulfate, 4303 Trifluoroacetyl hypochlorite, 0591 Trifluoroacetyl hypofluorite, 0629 See Acetyl hypobromite, Propionyl hypobromite... 

Reactions of 3-te/V-butylcyclohexene with, e.g., acetyl hypobromite, hypobromous acid and /V-chlorosuccinimide show diastereoselectivity in the electrophilic attack similar to that observed in the epoxidation (trimsIds obsd 90 10 calcd 77 23168), with the expected overall inversion of selectivity of epoxide formation, to give ct.y-6109. 

The reaction with A -bromosuccinimide or Af-bromoacetamide with or without added acid, on the other hand, leads predominantly to the same epoxide trans-6 as formed in the reaction with peracids. It is proposed that in the formation of cis-6 with acetyl hypobromite, hypobromous acid or A -chlorosuccinimide, nucleophilic attack of the halonium ion is fast. The epoxide ratio therefore is governed by the kinetically favored tran.v-halohydrin. However, in the reaction with A -bromosuccinimide or A -bromoacetamide the nucleophilic attack on the bromonium ion species becomes rate determining, attack of the nucleophile therefore follows the path of lowest activation energy. This is the attack on the c/.v-bromonium ion distant to the bulky tert-butyl group leading to the trans-diaxial bromohydrin, according to the Fiirst-Plattner rule, hence giving trans-6. 

This stereochemical character is shared by all addition reactions involving a halonium ion, so that mixed halogens e.g. Br-F [8g], Br Cl [go], I Cl [gi] and I F [g2]), and also reagents like hypobromous acid (Br-OH) [gs], acetyl hypobromite (CH3CO OBr) [g4] and iodine isocyanate (I NCO) [gs] lead to diaxial addition products, with the... 

The isolated alkenes undergo normal additions, frequently with high regio- and stereoselectivity. For example, methyl 4,6-0-benzylidene-2,3-dideoxy-a-D-eryi/2w-hex-2-enopyranoside 87 gives the 2,3-dibromo-D-a(fro-adduct 88 on treatment with bromine, and the 2-0-acetyl-3-bromo-3-deoxy adduct 89 is obtained when treated with acetyl hypobromite (O Scheme 46), indicating that the reactive bromonium ion intermediate is formed on the lower (a) face of the ring [78]. 

Halohydrinatton Acetyl hypobromite. N-Bromoacetamide. N-Bromosuccinimide. r-Butyl hypobromite. 

Acetylhydroxy-L-proline, 1014 Acetyl hypobromite, 12-13 N-Acetylimidazole, 13 S-Acetylmercaptosuccinic anhydride, 13 Acetyl methyl ursolate, 823... 

Other additions to the double bond of compounds in this series have not been studied extensively, but reports now indicate that several such additions can be accomplished efficiently. Nitryl iodide is, however, not added92 to the double bond of compound 45, but bromination in methanol, in the presence of barium carbonate, gives crystalline methyl 4,6-0-benzylidene-2,3-dibromo-2,3-dideoxy-a-D-altropyranoside in 70% yield.93 On treatment with potassium tert-butoxide in refluxing xylene, this compound undergoes elimination of the elements of hydrogen bromide to give methyl 4,6-O-benzylidene-2-bromo-2,3-dideoxy-a-D-t/ireo-hex-3-enopyranoside (46, R = Br) in 90% yield. Likewise, compound 45 reacts with acetyl hypobromite to give methyl 3-0-acetyl-4,6-0-benzylidene-2-bromo-2-deoxy-a-D-glu-... 

Both of the above equilibria lie to the left, but acetyl hypobromite is sufficiently reactive that it is the principal halogenating species in both solutions. The reactivity of the acyl hypohalites as halogenating agents increases with the ability of the carboxylate to function as a leaving group. This is, of course, correlated with the acidity of the carboxylic acid. The estimated order of reactivity of Br2, CH3C02Br, and CF3C02Br is... 

A mixture of N-tert-butyl-4-nitrobenzamide and a soln. of acetyl hypobromite prepared from Ag-acetate and bromine in CCI4 stirred 15 min. at room temp, protected from light by aluminum foil N-bromo-N-t rt-butyl-4-nitrobenzamide. Y 99%. - F. e., also N,N-dibromination, s. T. R. Beebe and J. W. Wolfe, J. Org. Chem. 35, 2056 (1970). 

The reagent can also be formed by reaction of bromine with mercuric acetate Hg(OAc)2 + Brz Hg(OAc)Br + CHjCOjBr Both equilibria lie to the left, but the acetyl hypobromite is suflSdently reactive that it... 

Bromination can also be carried out using solutions of acetyl hypobromite or... 

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