Formic acid 6-bromo

Bromo-4-methoxy-A-homo-estra-2,4,5(10)-trien-17-one (44 0. 2g), is dissolved in formic acid, 2 ml of boron trifluoride etherate is added and the mixture is stirred vigorously at 0° for 2 hr. A brown mass ca. 0.12 g) is obtained after evaporation of the solvents at reduced pressure. This material is diluted with water and extracted with chloroform. The chloroform extracts are washed successively with water and saturated salt solution, dried over anhydrous magnesium sulfate and evaporated at reduced pressure to give 95 mg of a product which is purified by filtration through a column of neutral alumina and crystallization of the residue after evaporation of the solvent from ethyl acetate-petroleum ether. The resulting A-homo-estra-l(10),2,4a-triene-4,17-dione (45), mp 143-146°, is identical to the tropone (45) prepared from monoadduct 17-ketone (43a). 

The synthesis of porphyrins from dipyrrylmethenes was first developed by Fischer42 and his collaborators. Different variants of this method are available. For the preparation of centrosym-metric porphyrins 7, the self-condensation of 5-bromo-5 -methyldipyrrylmethene hydrobromides or perbromides 6 in organic acid melts like succinic acid, tartaric acid or formic acid at temperatures up to 200 °C can be used. 

The rigorous temperature of these procedures can be avoided when 5-bromo-5 -(bromomcth-yl)dipyrrylmethene hydrobromides 12 a, 5-bromo-5 -(bromomethyl)dipyrrylmethene perbrom-ides 12b or a mixture of both are used, instead of 5-bromo-5 -methyldipyrrylmethene hydrobromides 6. These compounds 12 can be cyclodimerized by heating in formic acid to produce porphyrins. 

The reaction of 6-bromo-7-chloro-2-hydrazinobenzothiazole 402 with formic acid gives the corresponding 11,2,4]triazolo[3,2-/dbenzothiazole derivative 403 (unreported yield) (Equation 78) <2000IJH275>, a particular and surprising reactivity that has some precedents <1971JOC10, 1985JHC831>. 

Following earlier studies of the oxidation of formic and oxalic acids by pyridinium fluoro-, chloro-, and bromo-chromates, Banerji and co-workers have smdied the kinetics of oxidation of these acids by 2, 2Tbipyridinium chlorochromate (BPCC) to C02. The formation constant of the initially formed BPCC-formic acid complex shows little dependence on the solvent, whilst a more variable rate constant for its decomposition to products correlates well with the cation-solvating power. This indicates the formation of an electron-deficient carbon centre in the transition state, possibly due to hydride transfer in an anhydride intermediate HCOO—Cr(=0)(0H)(Cl)—O—bpyH. A cyclic intermediate complex, in which oxalic acid acts as a bidentate ligand, is proposed to account for the unfavourable entropy term observed in the oxidation of this acid. 

Chemical cleavage at selective amino acid residues is an alternative method for scission of peptide bonds in target molecules. Cleavage at the Met-Xaa bond is achieved by CNBr, at the Trp-Xaa bond by the tryptophan-directed reagent 3-bromo-3-methyl-2-[(2-nitro-phenyl)sulfanyl]-3//-indole (BNPS-skatole) and at the Asp-Xaa bond by 2% formic acid.123 24 All these reactions are carried out at acidic pH under standard conditions for each reagent. 

Bromo-3(or l)-methyl-5 lO-dihydrophenarsazine is obtained by the action of bromine on the reduced product formed by treating the lO-ehloro-eompouiul with formic acid. It forms yellow needles melting with ch eompusition at about 220° C. In a similar manner () io(lo- i ov M)-dihi/dr()phe (inazine is isolated as... 

Sanger and Thompson (1963) also reported the high voltage electrophoretic migrations of the halogenated derivatives at pH 1.85 (2 % formic acid, 8 % acetic acid, 1 hr at 4000 volts this system should be comparable to the pH 1.9 electrophoresis described in the Appendix). All migrate slower than tyrosine in this system tyrosine, 22.5 cm 3-chlorotyrosine, 19.3 cm 3,5-dichlorotyrosine, 16.5 cm 3-bromo-tyrosine, 18.0 cm 3,5-dibromotyrosine, 14.8 cm 3-iodotyrosine,... 

Self-condensation of l-bromo-9-methyldipyrromethenes (e.g., (51a)) in hot formic acid or in fused organic acid melts (succinic, tartaric, etc.) at temperatures sometimes exceeding 200 °C affords... 

Treatment of neopine hydrobromide in aqueous formic acid with hydrogen peroxide affords 1-bromoneopino, which can be degraded to 1-bromo / . oodeimethine [2],... 

Bromo-l-ethoxyethan-l-oxy)-linked TmtaGd resin (83) To remove residual poly (ethylene glycol) from the commercially available TentaGel HL-OH resin (130 pm, 0.41 mmol OH g ), a suspension of the resin (100 g, 41 mmol) in formic acid (500 mL, 13.3 mol) was stirred at 60 °C for 14 h. The mixture was then filtered, and the resin was thoroughly washed with dioxane (1.5 L) and then treated with 1 m NaOH (300 mL, 300 mmol). After 4 h, the resin was washed with water (1 L), MeOH (1.5 L), and dioxane (1.5 L) to give the PEG-free solid support. 

The ammonium formate in formic acid procedure has rendered possible the first preparation of isomeric 4,5-disubstituted oxazoles.03101 Bredereck, Gompper, and Reich101 have reported the anomalous behavior of certain long-chain a-bromo ketones a single a-bromo ketone on reaction with ammonium formate in formic acid gives a mixture of two isomeric oxazoles. Refluxing of a-bromo ketones or of a-chloro-/3-keto esters with ammonium acetate in acetic acid results in the formation of substituted 2-methyl-oxazoles.40 102 Ethyl a-chloroacetoacetate on heating with ammonium carbonate or formamide in formic acid yields 4-methyloxazole-5-carboxylic ester.40 103... 

A decade later Cleare and GriflBth (13) reported that the reaction of concentrated hydrohalic and formic acids with hexachloroiridate(IV) results in the formation of diamagnetic needle crystals of [Ir2( 00)4X4] " stoichiometry which exhibit metallic reflections. In accord with the work of Malatesta and Canziani (12), they prepared the bromo complexes as well as complexes containing different cations, but they did not prepare complexes containing more than four halides. To account for the observed diamagnetism, they proposed a planar tetranuclear structure based on the structure of the isoelectronic Re4(CO)ie ion (14). 

Metal/halogen exchange with 2,5-dibromopyridine leads exclusively and efficiently to 2-bromo-5-lithiopyridine in a thermodynamically controlled process it has been suggested that the 2-pyridyl anion is destabilised by electrostatic repulsion between nitrogen lone pair and the adjacent anion " this same factor is probably important in the greater difficulty found in generating 2,3-pyridyne (see section 5.3.2). The example below illustrates the use of the Weinreb amide of formic acid as a formyl-transfer reagent. ... 

Heating 5-bromo-2,3-diaminoPy with 98% formic acid gives 5-Br-2,3-di-formylaminopyridine, whereas reaction between the same diamine with acetic anhydride results in diacetylaminopyridine, which quickly affords IPs (48JCS1389) on heating at 315 °C. 

To a solution of 0.5 mL CCI4 containing 0.0358 g 2-buten-2-yl tosylate (0.01585 mmol) cooled in an ice bath was added 0.025 g bromine (0.1585 mmol) the mixture was kept cold until the completion of the addition. Evaporation of solvent gave the crude product. The flask containing erythro-2,3-dibromo-2-butyl tosylate was added the 0.125 M buffer of formic acid-sodium formate, and the reaction was monitored to completion. Then the solution was neutralized with NaHCOs and extracted with CCI4. Removal of the solvent afforded 3-bromo-2-butanone. (Note No complete experimental procedure was given in the original literature.)... 

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