Ethanol, 2-bromo acetate

On treatment of both quinoline and pyridine /V-oxides with bromine and thallium(iil) acetate, y-bromo-derivatives are formed pyridine JV-oxides are the less reactive substrates/ The reaction of 8-methoxyquinoline iV-oxide with acetic anhydride and methanol yields 84% of 2,8-dimethoxyquinoline. Similarly, the reaction of the 6-methoxy-iV-oxide and ethanol and acetic anhydride gives 2-ethoxy-6-methoxyquinoline, but, under the same conditions, the 7-methoxy-N-oxide is unchanged/ The Reissert compounds (149) derived from substituted quinolines, on treatment with thallium(lll) nitrate and trimethyl orthoformate, undergo either smooth ring-contraction or oxidative debenzoyl-ation, depending on the substitution pattern in the aromatic ring (Scheme 61)/ ... 

This dithiocarbonate is prepared in 92% yield by the reaction of ethyl bromo-acetate with carbon disulfide, ethanol, and KOH. 

A variety of conditions has been used to prepare oxiranes from trans-hxomo-hydrins. In general, bromohydrins are heated in a solution of 5-10% methanolic potassium hydroxide for 30 min to 8 hr. Longer reflux times are required for bromohydrins which are not anti-coplanar, e.g., diequatorial bromohydrins. A 5 % solution of potassium acetate in boiling ethanol can be used to cyclize steroidal bromohydrins containing base sensitive groups. The use of 1.1 equivalents of sodium methoxide per equivalent of steroid in methanol solution is especially recommended for 9a-bromo-l lj5-hydroxy steroids. 

Attempts to brominate benzothiazoles with bromine in acetic acid at room temperature have given only perbromides, but when these were heated in ethanolic solution, products in which bromine had substituted in the benzene moiety were detected. At 100°C bromine in acetic acid gave rise to the 4,6-dibromo derivative in accord with calculated -densities (70BSF2705). Vapor-phase bromination gave the 2-bromo product (84MI27). 

A subsequent elimination of hydrogen halide prompted by the lability of halogen on the carbon attached to nitrogen, a second halogen addition, and a repetition of the cycle must account for the reported formation of 9-pentachloro- and 9-pentabromoethylcarbazoles on reaction with excess halogen in methanol and acetic acid, respectively. Addition of bromine to IV-vinylcarbazole in benzene as solvent was accompanied by 3,6-dibromi-nation in ethanol, 3,6-dibromo-9-(2-bromo-l-ethoxyethyl)carbazole was reportedly formed (cf. ref. 230). 

Another work of Duhamel and Ancel [59] related this synthesis of retinal via (3-ionylideneacetaldehyde. Condensation of methallyl-magnesium chloride with diethyl phenyl orthoformate (EtC CHOPh) led after bromination of the ene-acetal, deshydrohalogenation (NaOH 50%), ethanol elimination with hexamethyldisilazane (HMDS) and ISiMes, to the bromo-dienol ether. This latter was submitted to bromine lithium exchange and the lithio enol ether was then condensed with p ionylideneacetaldehyde to give retinal, Fig. (28). 

Bromomethyl ketones.l Reaction of (dibromomethyl)lithium (1) with esters and then with BuLi (excess) generates the enolate (a) of a bromomethyl ketone. Quenching with acidic ethanol gives the bromomethyl ketone (2) in 70-85% yield. Quenching with A O generates bromo enol acetates. 

Dissolve 1.0 g of the compound in 10-15 ml of glacial acetic acid, cautiously add a solution of 3-4 ml of liquid bromine in 10-15 ml of glacial acetic acid until the colour of bromine persists and allow the mixture to stand for 15-20 minutes. Pour into 50-100 ml of water, filter off the bromo compound at the pump and wash with a little cold water. Recrystallise from dilute ethanol. Alternatively dissolve 1.0 g of the phenol in water, ethanol or acetone and add slowly, with constant shaking, just sufficient of a bromine solution (prepared by adding 5g of bromine to a solution of 7.5 g of potassium bromide in 50 ml of water) to impart a yellow colour to the mixture. Allow to stand for 5 minutes. Add about 50 ml of water, and shake vigorously to break up any lumps. Filter and wash the bromo derivative with a dilute solution of sodium metabisulphite. Recrystallise from ethanol or from dilute ethanol. 

Chiralcel OJ column with methanol, ethanol, and hexane-ethanol (40 60, v/v) as the mobile phases separately and respectively, (b) Effects of temperature (van t Hoff plot) on the resolution of itt -2-(4-bromo-2-fluorobenzyl)-(1,2,3,4-tetrahydropyrrolo 1,2-a]pyra-zine-4-spiro-3 -pyrrolidine)-l,2, 3,5 -tetrone on a Chiralpak AD-RH column mobile phase was 0.01 M acetate buffer (pH 4.7)-acetonitrile (50 50, v/v). (From Ref. 95.)... 

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