Carbon tetrabromide esters

AP951). Alternatively, reduction of the ester in 586 gave the alcohol 587 that upon reaction with carbon tetrabromide/triphenylphosphine gave the respective bromide which was cyclized under the reaction condition to give 588 (92JMC1076) (Scheme 98). 

Benzo[b]furan-3-carboxyUc esters. Cyclization and alkoxycarbonylation is observed when 2-alkynylphenols are exposed to Pdl2-thiourea-CBr4 under CO and in the presence of CsiCOi. Carbon tetrabromide serves as the reoxidant of Pd(0) species. 

By the employment of other bromides O-desmethylmycophenolic acid was obtained. Thus, the C7 bromoester methyl 6-bromo-4-methylhex-4-enoate, BrCH2CH=C(Me)CH2CH2C02Me, was prepared from tritylgeraniol which was first converted in several steps to the terminal diol, Malaprade oxidation of which furnished 4-methy-6-trityloxylhex-4-enal. Mild oxidation to, the corresponding acid with silver oxide, formation of the methyl ester with diazomethane and derivation of the required allylic bromide by treatment of the alcohol, liberated from the trityl derivative, with carbon tetrabromide containing triphenylphosphine completed the synthesis. 

In order to introduce diversity at the PI position, intermediate 73a was constructed from the corresponding polymer-bound pyrrolidine amide 80 (Scheme 18). Anchoring of pyrrolidine amide 78 (MMT = mono-/ -meth-oxytrityl), which was prepared in four steps (76% overall yield) from commercially available (S)-methyl ester isopropylideneglycerate (77a) to (ben-zyloxy)benzyl bromide resin 79 (prepared from Wang resin by treatment with carbon tetrabromide and triphenylphosphine [150]), proceeded in 84% loading yield with minimal racemization (<2%) [151]. 

Carbonothioic acid, 0-(6-chloro-3-phenyl-4-pyridazinyl) S-octyl ester. See Pyridate, Carbonothioic dichloride. See Thiophosgene Carbon oxide. See Carbon monoxide Carbon oxide sulfide. See Carbonyl sulfide Carbon oxychloride. See Phosgene Carbon oxysulfide. See Carbonyl sulfide Carbon silicide. See Silicon carbide Carbon sulfide. See Carbon disulfide Carbon tet. See Carbon tetrachloride Carbon tetraboride. See Boron carbide Carbon tetrabromide CAS 558-13-4 EINECS/ELINCS 209-189-6 UN 2516... 

Treatment of peracylated sugar lactones as shown in Scheme 3 gives terminally-iodinated methyl aldonates. The suggested sequence of events is indicated 1,4-lactones behaved similarly, as did O-pivaloyl or (7-benzoyl derivatives, and woik-up with ethanol gave ethyl esters.l Methyl 4-bromo-4-deoxy-L-threonate (22) has been prepared by oxidative degradation of L-ascorbic acid, and introduction of bromine using TPP-carbon tetrabromide.l ... 

It melts at 39°C and may be purified by vacuum sublimation. The Hquid boils at 233°C to give a monomeric vapor in which the Ti—Br distance is 231 pm. Titanium tetrabromide is soluble in dry chloroform, carbon tetrachloride, ether, and alcohol. Like titanium tetrachloride, TiBr forms a range of adducts with molecules such as ammonia, amines, nitrogen heterocycles, esters, and ethers. 

The zirconium tetrahalides react with esters to form ZrX4 2 ester adducts (302, 303, 330, 407-410, 412) in which, coordination number six is attained. On the basis of dipole moments (Table XIII), it is concluded that the adducts have the cis structure. This has been supported, at least in the case of ZrCl4 2011300 0 02115, by the infrared spectrum (330). Oryoscopic studies in benzene solution of the 2 1 adducts of zirconium tetrachloride and ethyl formate, ethyl acetate, and ethyl butryrate show that these complexes tend to decompose to the 1 1 species, the extent of dissociation increasing with the number of carbon atoms in the acid radical. The estimated dissociation constant is about 5 x 10", whereas for the ethyl acetate adduct of zirconium tetrabromide it is only 2 X 10". The approximate dissociation constant of the complex zirconium tetraiodide 2 ethyl acetate is 3.5 x 10". The 1 1 species were synthesized by direct reaction in benzene with strictly stoichiometric ratios of the reactants. Oryoscopic determination of molecular weights of the 1 1 complexes indicate that these complexes generally... 

Another interesting synthetic approach which also constitutes a total synthesis was accomplished by Pace (4 ). Sodium acetoacetic ester was oxidized with iodine, the product saponified, and carbon dioxide eliminated to give 2,5-hexanedione. The diketone was reduced to the diol, which was transformed to the dibromide. The hexadiene was formed and converted to the tetrabromide and subsequently to the hexabromide, which upon treatment with alcoholic potassium hydroxide gave DL-mannitol. 

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