Hydrogen bromide-Acetic acid

Hg(OAc)2, H2O, 80% AcOH, HSCH2CH2SH, 25°, 5-20 min H2S, 2 h, high yield. The removal of an 5-benzylthiomethyl protective group from a dithioacetal with mercuiy(II) acetate avoids certain side reactions that occur when an 5-benzyl thioether is cleaved with sodium/ammonia. The dithioacetal is stable to hydrogen bromide/acetic acid used to cleave benzyl carbamates. 

NKOH, EtOH, 20°, 5-10 min 80% yield. 5-2,2-Bis(carboethoxy)ethyl thioether, stable to acidic reagents such as trifluoroacetic acid and hydrogen bromide/acetic acid, has been used in a synthesis of glutathione. ... 

Polyphosphoric acid is a commonly used catalyst for this reaction however, in some cases a mixture of hydrogen bromide/acetic acid gives better results. Acylation of the S-phenyl-, V-(4-tolyl)- or S-(l-naphthyl)-substituted thiobenzenepyruvic acids 3a-c affords the corresponding dibenzo[A,/]thiepins in satisfactory yields, while reaction of the S-(4-methoxyphenyl) or S-(2-naphthyl) derivatives fails to provide any thiepin.60 The intramolecular Friedel-Crafts acylation of 2-(arylsulfanyl)benzeneacetic acids also yields the corrresponding dibenzothiepins in this case the use of hydrogen fluoride sometimes results in purer products.38 The applicability of this method is restricted to the synthesis of stable bisannulated thiepins. 

In the heptonolactone series, D-glycero-D-gulo-heptoao-1,4-lactone reacted with hydrogen bromide-acetic acid to afford (44) 2,7-dibromo-2,7-dideoxy-D-g/ycero-D-zWo-heptono-1,4-lactone (35), together with two anhy-... 

Usable, though frequently less satisfactory, because of complications, is the action of hydrogen bromide-acetic acid on sulfonic esters of 1,2-0-... 

S. Dimitrijevich and N. F. Taylor, The synthesis and reactions of unsaturated sugars, Part 3. The action of hydrogen bromide-acetic acid on methyl 4-0-benzyl-2,3-dideoxy-6-O-trityl-a-D-ern/jro-hex-2-enoside, Carbohydr. Res., 20 (1971) 427-430. 

A reaction, that does not involve the enediol takes place on halogenation. Treatment of 138 with hydrogen bromide-acetic acid affords 5-0-acetyl-6-bromo-6-deoxy-L-ascorbic acid (166).360 Compound 166 was used for the synthesis of 6-substituted derivatives of 138, via the 5,6-anhydro derivative.361... 

Benzoyl-4-chlorophenyl-carbamoylmethyl)carbamic acid benzyl ester Hydrogen bromide Acetic acid... 

Hydrogen bromide-acetic acid was purchased from BOH Chemicals Ltd., Poole, England, The checkers used hydrobromic acid (30-32% 1n acetic acid, 4.1 M) from Fisher Scientific, 711 Forbes Ave., Pittsburgh, PA 15219. 

The synthesis of C-dihydrotoxiferine I has also been achieved. When the Wieland-Gumlich aldehyde (LXV) was treated with hydrogen bromide, acetic acid, and phosphorus, it yielded the 18-bromo derivative (LXXVIII R = Br), which without isolation was debrominated with zinc and acetic acid. The resulting amorphous aldehyde (LXXVIII R = Hor stereoisomer) was converted into its iVb-metho salt which was... 

Add phenol (25 g) to a solution of the ditosylamide (12.5 g, 0.026 mol) in hydrogen bromide-acetic acid (45%, 250 mL) in a single-necked round-bottomed flask equipped with a magnetic stirrer bar and a reflux condenser surmounted by an air condenser.0 Heat and stir the mixture at 80°C for 36 h. 

The hydrogen bromide, acetic acid, and acetic anhydride are then removed from the straw-yellow solution by distillation under reduced pressure a water bath whose temperature does not exceed 60° should be used to heat the mixture (Note 5). During the distillation the solution becomes slightly darker. When no further distillate comes over, or when the residue crystallizes, distillation is stopped, 250-300 cc. of dry isopropyl ether is added (Note 6), and the flask is warmed carefully on a water bath to hasten solution of the product (Note 7). The hot solution is transferred to a 1-1. Erlenmeyer flask and is cooled rapidly, with cold water, to about 45°. The mixture is then allowed to cool slowly to room temperature and is finally placed in a refrigerator at 5° for two or more hours. The acetobromoglucose is collected on a Buchner funnel, pressed into a firm cake, and washed with about 50 cc. of dry isopropyl ether. The white crystalline material, after drying in vacuo over calcium (or sodium) hydroxide, weighs 110-120 g. (80-87 per cent of the theoretical amount) (Note 8). 

The 1,2,3-trihydroxypropyl side chain of pyrazol-3-ones 92a,b was efficiently brominated at positions 2 and 3 by reaction with hydrogen bromide acetic acid. The products, 2,3-dibromopropyl acetates 93a,b were obtained in 71% and 70% yield, respectively (88PHA77) (Scheme 25). 

Reaction of hydrogen bromide-acetic acid with the diacetal of 5,6-an-hydro-aZZo-inositol (76) gives the meto-dibromotetrol (77) tetraacetate, crystals of which are isolable from the reaction mixture. This result is surprising because the diastereomeric anhydroinositol diacetal (96) gave, under the same conditions, only monobromo products. The structure and configuration dl(1234/56) (77) were established by variable-temperature, nuclear magnetic resonance and spin-decoupling (see p. 56). ... 

---