Acetyl bromide-acetic anhydride

Hydrogenation was carried out at O to minimize decarboxylation of the saturated 3-keto acid product 18. Mannich reaction proceeded with in situ decarboxylation to afford a-methylene ketone 19, which on Michael reaction with ketal 3 keto ester 20 -" yielded adduct 21. Saponification, B ring closure, and decarboxylation then led to ketalenone 23 in high yield, which was converted into ( + )-19-nortestosterone 24 and thence to ( + )-19-norandrostenedione 25 in 50% yield from 18 or 27% overall yield from 12. However, ketal hydrolysis, A ring closure, oxidation at C-17, and isomerization by the Roussel procedure (acetyl bromide-acetic anhydride in methylene chloride at 20°) should yield (-f )-estrone 26 efficiently. 

Cyclization of enone (9) in hexane with boron trifluorideetherate in presence of 1,2-ethanedithiol, followed by hydrolysis with mercury (II) chloride in acetonitrile, yielded the cis-isomer (10) (16%) and transisomer (11) (28%). Reduction of (10) with lithium aluminium hydride in tetrahydrofuran followed by acetylation with acetic anhydride and pyridine gave two epimeric acetates (12) (32%) and (13) (52%) whose configuration was determined by NMR spectroscopy. Oxidation of (12) with Jones reagent afforded ketone (14) which was converted to the a, 3-unsaturated ketone (15) by bromination with pyridinium tribromide in dichloromethane followed by dehydrobromination with lithium carbonate and lithium bromide in dimethylformamide. Ketone (15), on catalytic hydrogenation with Pd-C in the presence of perchloric acid, produced compound (16) (72%) and (14) (17%). The compound (16) was converted to alcohol (17) by reduction with lithium aluminium hydride. 

The a proton of a substituted cyclopropane is also rendered acidic if the substituent is attached to the ring by C-P bonds. A few reports have appeared on a-substitution in such compounds.(Cyclopropyl)triphenylphosphonium bromide was converted to a (1-ethoxy-carbonylcyclopropyl)triphenylphosphonium salt 18 in 80% yield by sequential treatment with lithium diisopropylamide and ethyl chloroformate. Furthermore, some diethyl cyclopropyl-phosphonates were converted, in some cases in excellent yield, to diethyl (1-hydroxymethyl-cyclopropyl)phosphonates by treatment with lithium diisopropylamide followed by addition of an aldehyde." Thus, typically, diethyl 2-hexylcyclopropylphosphonate gave diethyl 2-hexyl-l-[hydroxy(phenyl)methyl] cyclopropylphosphonate (19b) in 90% yield on reaction with benzaldehyde. ° Other electrophiles such as acetone, acetyl chloride, acetic anhydride, and ethyl acetate, were not sufficiently reactive to undergo addition to the anion. 

The tosyl derivative of the R and the S forms of 6-benzyloxy-2,5,7,8-tetramethylchroman-2-ethanol was then reacted with the respective 0 4 alkylmagnesium bromide and the final stereoisomer obtained as the acetate after catalytic hydrogenolysis and acetylation with acetic anhydride/pyridine in good yield in all cases. 

Nitrophenol, dissolved in sodium hydroxide solution, is subjeeted to condensation with ethyl bromide and the resulting /7-nitrophenetole is reduced with suitable reductant. The / -phenetidine thus obtained is acetylated with acetic anhydride to yield the official compound. 

Aminophenol is obtained by treating aniline with sulphuric acid and potassium hydroxide, which on acetylation with acetic anhydride yields the />-hydroxy acetanilide. The resulting product on ethylation with ethyl bromide forms phenacetin. 

Ethoxy nitrobenzene is prepared from ehlorobenzene by its nitration followed by treatment with sodium ethoxide, whieh on reduetion yields/(-phenetidine. The resulting product is diazotised with nitrous aeid at 0°C reaeted with phenol, ethyl bromide and reduced to obtain two moles of/(-phenetidine which upon acetylation with acetic anhydride yields two moles of phenacetin. 

Annulene undergoes addition reactions with bromine or with maleic anhydride thus its simple chemistry differs markedly from that of benzene [16]. Under special conditions it gives reactions which provide products typical of electrophilic substitution, but these reactions may not proceed by straightforward electrophilic substitution mechanisms. Thus it may be acetylated with acetic anhydride - boron trifluoride [52], and nitrated with copper(ll) nitrate in acetic anhydride, giving a mixture of dinitro-isomers [52,53]. Pyridinium bromide perbromide provided either monobromo-... 

It is often possible to prepare the acylglycosyl bromide from the sugar without isolation of the intermediary poly-O-acetate. In one such method , the sugar is acetylated with acetic anhydride and perchloric acid, and when reaction is complete, hydrogen bromide is generated in situ from phosphorus tribromide, itself prepared by adding phosphorus and bromine to the reaction mixture. 

Cyclization of a-cyanoalkyl cyanamides (74) with hydrogen bromide gave 4-aminoimidazoles (77) as their hydrobromide salts. These compounds (77) were found to be unstable as the free base but gave stable (V-acetyl derivatives (84 R2 = Br, R3 = COCH3) (33-82%) when treated with acetic anhydride in pyridine (64JOC153 66CA12211). 

Selective replacement of hydroxyl groups by bromine has been reported for some inositols and inosamines. DL-2-Amino-2-deoxy-epi-inositol hydrochloride plus acetyl bromide in acetic anhydride gave, after 6 hours at 150°, DL-4-acetamido-l,2,6-tri-0-acetyl-3,5-dibromo-3,4,5-trideoxy-c/uro-inositol in 32% yield, the bromine atoms having been introduced with inversion.407 Under related conditions, DL-epi-... 

Potable water and raw source water Sample acetylated in situ by addition of acetic anhydride, solvent extracted and concentrated alternatively, extracted acidic sample derivatized by pentafluorobenzyl bromide and cleaned up by column chromatography HRGC-ECD (for pentafluorobenzyl derivative) HRGC-MS (for acetyl derivative) <50 ng/L (pentafluorobenzyl) <50 ng/L (acetyl derivative) 10-64% (pentafluorobenzyl derivative) 70-132% (acetyl derivative) Sitholeetal. 1986... 

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