Phenacyl bromide, 4-bromo

Phenyl- and 5-aryl-2-benzyl-6//-l,3,4-thiadiazincs 8 (R3 = Ph, Bn) are prepared by condensation of thiobenzohydrazide or phenylthioacetic acid hydrazide with a-halocarbonyl compounds.10, 50 Under appropriate conditions it is also possible to isolate the primarily formed 4,5-dihydro-6//-1,3,4-thiadiazin-5-ol intermediates 7a-h. For this purpose, the thiohydrazide is added to an equimolar amount of sodium ethoxide solution, then at — 25 °C an ethanolic solution of the respective phenacyl bromide, 2-bromo-l,2-diphenylethan-l-one, 2-bromo-l-phenylpropan-l-one, or 2-bromo-l-phenylbutan-l-one is added. The 4,5-dihydro-6//-l,3,4-thiadiazin-5-ols 7 separate as colorless precipitates. They undergo partial dehydration at room temperature to the 2-phenyl- or 2-benzyl-6//-l, 3,4-thiadiazines 8 on heating for about 5-7 minutes in ethanol or chloroform, the dehydration is complete. 

The course of the reaction of phenacyl bromides (39) with nickel carbonyl is markedly dependent on the solvent employed in tetrahydrofuran the products are 1,2-dibenzoylethanes (cf. 40) but in dimethylformamide, 2,5-diarylfurans (41) are obtained in moderate to excellent yield (Scheme 53).90 It is possible that the furan derivatives (41) arise via intermediate fi,y-epoxyketones which can be isolated as products from a number of a-bromo-ketone substrates [cf. 39 and Section II].28... 

Heating to reflux a pyridine solution of 3-substituted-5-(l-aroyl-l-bromo)methylthio-4-phenylamino-4//-[l,2,4]tria-zoles 81 (available from the corresponding 1,2,4-triazoles with phenacyl bromides and subsequent ultraviolet (UV) light-induced bromination) affords 3-substituted-6-aroyl-5,6-dihydro-5-phenyl[l,2,4]triazolo[3,4-6][l,3,4]thiadiazoles 82 (Equation 19) <1993IJH135>. 

Barba and coworkers [84-91] have published a number of papers dealing with novel syntheses based on the reduction of phenacyl bromides. Electrolysis of phenacyl bromide at a mercury cathode leads to an intermediate, which reacts to give 2,4-diphenylfuran [84]. However, when a proton donor (CH3OH) is present, the reduction of phenacyl bromide yields acetophenone and 2-bromo-l,3-diphenyl-3,4-epoxy-butan-l-one. Interestingly, if phenacyl bromide is slowly introduced into an electrolysis cell so that the unreduced starting material is maintained at a low concentration, the products are different [85] (Scheme 7). 

In a 500-cc. flask are placed 50 g. (0.25 mole) of />-bromoaceto-phenone (Org. Syn. 5, 17) and 100 cc. of glacial acetic acid. To the resulting solution is very slowly added 40 g. (0.25 mole) of bromine, keeping the temperature below 20°. The mixture is vigorously shaken by hand during the addition. />-Bromo-phenacyl bromide begins to separate as needles when about one-half of the bromine has been added. The addition requires about thirty minutes. 

Alkylation of (585b) with a phenacyl bromide produced (589), which can be cyclized with hydrazine to (590) (77JHC59). Similar cyclizations have been carried out on a 1-phenacyl-2-brpmoimidazole derivative (74UKZ99), a l-phenacyl-2-methanesulfonyl-imidazole derivative (74CHE1492) and l-(2-chloroethyl)-2-bromo-4,5-diphenylimidazole (75CHE371) to afiford imidazo[2,l-c][l,2,4]triazines. 

Section II.7 describes some ring closures of the C-C-N-C-C, N-C-C-N-C-C, and N-C-C-N-C-C-N systems to give hydroxypyrazines (248, 365a, 477, 479, 480-483) more information can be found in reference 1054. Newbold and Spring (89) described the reaction of 2-bromo-A -(r-methyl-2 -oxopropyl)propionamide with ethanolic ammonia to give 2-hydroxy-3,5,6-trimethylpyrazine and Masaki et al. (551) have described the reaction of A -leucyl-6>-benzyIhydroxylamine (2) with phenacyl bromide in methanol saturated with ammonia to give 3-hydroxy-2-isobutyl-5-phenylpyrazine and 2,5-diphenylpyrazine. 

The oxidants dimethyl sulfoxide and nitroso compounds react easily with oL-bromo ketones and convert them into a-dicarbonyl compounds. The reaction with nitroso compounds is usually carried out in the presence of pyridine and proceeds through a nitrone stage. Phenacyl bromide (a-bromoacetophenone) is thus transformed first into phenacylpyridinium bromide and further, with nitrosobenzene, into a-ketoaldonitrone, which is subsequently treated with hydroxylamine to give phenylglyoxal monoxime or with phenylhydrazine to give phenylglyoxal osazone [985] (equation 411). 

Other compounds that have been similarly synthesized are 2,4-bis(4-methoxyphenyl)furan, 2,4-bis(4-biphenylyl)furan, 2,4-bis(4-bromophenyl)furan, 2,4-bis(4-chlorophenyl)furan, and 2,4-bis(4-nitrophenyl)furan. When MeOH (a proton donor) is added to the system containing phenacyl bromide [232], the principal products are acetophenone (53%) and 2-bromo-l,3-diphenyl-3,4-epoxy-butan-l-one (37%). If, to DMF containing lithium perchlorate and ethyl bromoacetate, phenacyl bromide is slowly introduced and reduced at mercury, the distribution of products is different [233] ... 

A noteworthy difference is observed in the condensation of thiosemicarbazide with aromatic a-halocarbonyl compounds in comparison to aliphatic a-halocarbonyl compounds. It has been found26 that the reaction of phenacyl bromide with thiosemicarbazide furnishes 5-phenyl-1,3,4-thiadiazin-2-amine together with a small amount of 5-phenylthiazolc-2-hydrazine, Similarly, the reactions of thiosemicarbazide with 2-bromo-l,2-diphenylethan-l-one,7 8,41 2-bro-mo-l-phenylpropan-l-one,10,41 and 2-bromo-l-phenylbutan-l-one 10,41 in ethanolic solution give 1,3,4-thiadizines. However, the main products are the thiazole-2-hydrazine derivatives (cf. Houben-Weyl, Vol. E8b, p 72ff). The addition of an equimolar amount of 48% hydro-bromic acid results in the exclusive formation of the 1,3,4-thiadiazines 2 a, c, and d. When the condensations of thiosemicarbazide with 2-bromo-l,2-diphenylethan-l-one, 2-bromo-1-phenylpropan-l-one or 2-bromo-l-phenylbutan-l-one are performed in ethanol at room temperature, the S-(oxoalkyl)-isothiosemicarbazide hydrobromides are formed as open-chain intermediates and also undergo cyclization in ethanol upon addition of an equimolar amount of 48% hydrobromic acid to furnish 2 a, c, and d. 

Thiosemicarbazides bearing a bulky alkyl substituent in the 4-position behave similarly. Thus, in reactions of 4-(2,2,4-trimethylpent-4-yl), 4-terZ-butyl- or 4-isopropylthiosemicarbazide with 2-bromo-l,2-diphenylethan-l-one, 2-bromo-l-phenylpropan-l-one, or phenacyl bromides, the 2-(alkylimino)-4-aryl-2,3-dihydrothiazol-3-amines are always formed as side products and, in the case of 4-isopropyllhiosemicarbazide, additional, small amounts of the corresponding 2-hydrazono-3-isopropyl-4-phenyl-2,3-dihydrothiazole are also obtained.10 These side products can be isolated preparatively by chromatographic workup on Sephadex LH-20.43... 

The following fluorescent alkylating agents have been introduced as pre-chromatographic reagents 9-bromo-methylacridine [480], 3-bromomethyl-6,7-dimethoxy-l-methyl-2(lH)-quinoxalinone [481], naphthacyl bromide (2-bromoacetonaphthone) [482, 483], p-(anthroyloxy)-phenacyl bromide (panacyl bromide) [484], 1-bromo-acetylpyrene [485], 9-chloromethy[anthracene [486], and 9-anthryldiazomethane [487, 488]. 

Benzylation of eucomin (3) with benzyl bromide and potassium carbonate in dimethyl formamide gives 5,7-di-O-benzyleucomin (43). If acetone is used as solvent additional C-benzylation at C-6 or C-8 takes place (25, 24). Again sodium acetate shows complete selectivity towards the activated hydroxyl at C-7 (64). Similarly 7-0(p-bromophenacyl)euco-mol (32) is isolated from the reaction of eucomol (10) with p-bromo-phenacyl bromide and sodium acetate or pivalate in acetone (74). 

Group II PLA2 p-Bromo-phenacyl-bromide 43 nM Cell permeable, irreversible ... 

Adding an alcoholic solution of phenacyl or 4-bromophenacyl bromide to[a solution of a carboxylic acid that has been neutralized with sodium carbonate gives an ester of a)-hydroxyaceto-phenone or of its 4-bromo derivative these esters crystallize well from ethanol and are useful for characterization of liquid acids. 

Other phenacyl reagents are p-bromophena-cyl bromide, or a-bromo-p-bromoacetophenone, p-chlorophenacyl bromide, or a-bromo-p-chloroace-tophenone, p-nitrophenacyl bromide, or a-bromo-p-nitroacetophenone, m-methoxyphenacyl bromide, or o-bromo-3-methoxyacetophenone. 

Comparable phenacyl esters are synthesized with p-bromophenacyl bromide or p-nitrophenacyl bromide with a similar spectroscopic behavior (both p-Bondapak C18). Useful derivatization by tagging the COOH group can also be done with a-bromo-2 -acetonaphthone resulting in well-soluble and strongly UV-absorbing (254 nm) naphthanyl esters after a reaction time of only 10 min at ambient temperature (LiChrosorb Si-100). Furthermore, coumarin derivatives (substituted at position 7 for higher fluorescence quantum yields) are predestinated to... 

Undecylenic acid was extracted from ointments and powders, derivatized with 4 -nitrophenacyl bromide, and analyzed on a Cg column (2 = 265 nm). A 50/30/20 methanol/acetonitrile/water mobile phase generated a 7 min elution [573]. A table of the effect on retention times of changing phenacyl derivatives (e.g., 4 -methyl, 4 -phenyl, 4 -bromo) and the column to a C,g is presented. The linear range was reported as 12.5-300 pg injected. 

Peel and Sutherland [34] synthesized the lactone acid (21) starting with the formation of the epimeric diformates by a Prins reaction of norbornadiene and paraformaldehyde to give (22a). Hydrolysis and Jones oxidation of (22a) then gave the keto acid (22b) which underwent ring opening with hydrogen bromide in acetic acid to the bromo compound (23). Baeyer—Villiger oxidation of the latter and addition of sulphuric acid to the reaction mixture followed by work up with alkali afforded an overall conversion to (21) of which the p-bromo-phenacyl ester was converted by the sequence — p-phenylbenzoylation, reduction with zinc and acetic acid and diborane reduction - to the alcohol (14d), previously taken forward to the aldehyde (lb) by Corey. 

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