A-Bromoacetophenone

Timolol maleate a-Bromoacetophenone Nomifensine maleate Bromoacetyl bromide Bromazepam Cephapirin sodium Clonazepam Flunitrazepam 5-Bromoacetyl salicylamide Labetalol HCI m-Bromoanisole Tramadol HCI p-Bromoanisole Cyclofenil Bromobenzene... 

Following the same solvent-free approach, the synthesis of 2-aminothia-zoles was described by short irradiation (2-3 min, approximate temperature 100-115 °C) of a mixture of thiourea and substituted a-bromoacetophenones, deposited over K2CO3 [9] (Scheme 8). 

When Sn2 reactions are carried out on these substrates, rates are greatly increased for certain nucleophiles (e.g., halide or halide-like ions), but decreased or essentially unaffected by others. For example, a-Chloroaceto-phenone (PhCOCH2Cl) reacts with KI in acetone at 75°C 32,000 times faster than l-Chlorobutane, ° but a-bromoacetophenone reacts with the nucleophile triethylamine 0.14 times as fast as iodomethane. The reasons for this varying behavior are not clear, but those nucleophiles that form a tight transition state (one in which bond making and bond breaking have proceeded to about the same extent) are more likely to accelerate the reac-tion. ... 

It was possible to effect lOOC reaction leading to six-membered rings, e.g., 220 in low yield (ca. 20%) by heating the reaction mixture at 110 °C (Eq. 22) [59]. In fact, Oppolzer and Keller [60] had previously reported the lOOC reaction of 219 to 220 in 20% yield by heating at 110 °C. Furthermore, the scope of these oxime-olefin cycloadditions has been extended to ketoximes, e.g., 221. The latter was prepared by amination of a-bromoacetophenone with allylamine 214a. Heating of 221 at 110 °C for 8 h led to cycloaddition with formation of the fused pyrrolidine 222 in 88% yield. As in Scheme 25, only one... 

The preparation of 2-amino-5-arylselenazoles 99 and 3,5-diaryl-1,2,4-selenadiazoles 101 has been described. Starting from readily available a-arylsulfonyl-a-bromoacetophenones 98 reaction with selenourea gave 2-amino-5-arylselenazoles 99 in good yield. Reaction of 98 with selenobenzamide 100 did not give the expected selenazole the 3,5-diaryl-1,2,4-selenadiazole 101 was obtained in moderate yield. Compound 101 is a known oxidation product of selenobenzamide and a mechanism for its formation is proposed <99JHC901>. 

Pinney et al. reported the synthesis of benzothiophene CA4 analogs and an example synthesis is given in Scheme 38 [83]. Benzothiophene (145) was produced by reacting aromatic thiol 146 with a-bromoacetophenone 147 to generate the sulfide 148. Compound 148 was then cyclized to the benzothiophene 149 using polyphosphoric acid and heat. Formation of 145 was achieved by Friedel-Crafts aroylation of 149 with the methoxybenzoyl chloride 144. 

In the middle of the 1950s, Knott reported the synthesis of dyesmffs based on benzothiazole derivatives. Alkylation of Al-methylbenzo-l,3-thiazole-2-thione with a-bromoacetophenone and deprotonation of the resulting thiocarbonylium salt 5 yielded, after spontaneous desulfurization of the intermediate thiirane (7), the alkylidene derivative 8 (18) (Scheme 5.1). In order to rationalize the reaction, thiocarbonyl ylide 6 was proposed as the precursor of thiirane 7. To the best of our... 

The single report of an oxygen- and sulfur-containing five-membered ring formed from a thiourea is that of Hartmann,211 who prepared the 1,3-oxathiolium salt 91 from a-bromoacetophenone and tetramethyl-thiourea. 

The aminouracil (196) reacts with a-bromoacetophenone in DMF to give only the product of initial C- alkylation (197). In acetic acid the product of N- alkylation (198) is formed as well (73CPB473). 2,6-Diaminopyridine hydrochloride reacts with acyloins under melt conditions (Bischler reaction). The product (199) or (200) depends on the molar ratio of the reactants <74JCS(Pl)l852). 

The azine derivative of a-bromoacetophenones has been used as the 1,6-dielectrophile along with malonate esters as the 1,1-dinucleophile has been used in the synthesis of 1,2-diazepines <1984CHEC(7)593, 1996CHEC-II(9)113>. 

Tebbe methylenation < 1978JA3611 > of a-bromoacetophenone resulted in the formation of allylic bromide 165, which upon reaction with benzenesulfonamide gave the 1,6-diene 166 (Scheme 35). The acyclic diene 166 underwent photooxidative cyclization to form 1,2,5-dioxazepine 167 <1996TL815>. 

Reaction of aryl selenoamides 274 with a-arylsulfonyl-a-bromoacetophenone 276 gave compound 79 in 44 47% yield (Equation 35) <1999JHC901>. 

To obtain more information on the nature of the quasiphosphonium intermediates involved in these systems we have studied the reactions gf sterically hindered neopentyl esters by means of 1P nmr spectroscopy. Trineopentyl phosphite and a-bromoacetophenone gave rise to a peak at +41 ppm due to the ketophosphonium intermediate 3 (R = Me.CCH, R = Ph X = Br ) within half an hour of mixingJthe reactants in acetone-dfi at 27 °C ( p nmr shifts are relative to 85% H-PO. down-field positive). Peaks due to the ketophospnonate 4 +19 ppm and the vinyl phosphate 7 (-7 ppm) were also observed (compound 4 and 7 have satisfactory elemental analysis and spectroscopic data ). The concentration of the intermediate reached a maximum after about two hours when it was precipitated from acetone solution by the addition of anhydrous ether to give white crystals of trineopentyloxy (phenacyl)phosphonium bromide, identified by elemental analysis and nmr spectroscopy ( XP 6+41, in CDCl ). When redissolved in acetone-dg, deuterochloroform, acetic acid, or acetic acid-acetone mixtures, the intermediate decomposed to yield keto-phosphonate 4 but none of the vinyl phosphate 6 (Perkow product). Nor was the course of reaction affected by the addition of chloride ion or of a-chloro-acetophenone in acetonitrile. 

Intermediates derived from dineopentyl phenyl-phosphonite and from neopentyl diphenylphosphinite were found to be considerably more stable. Reaction with a-bromoacetophenone gave the corresponding Arbuzov intermediates 9, 10 as crystalline solids, the diphenylphosphinite derivative 10 being sufficiently... 

By carrying out the reaction of trineopentyl phosphite with a-bromoacetophenone in the presence of acetic acid (10% in acetone-d ) we have also obtained evidence for the transient existence of the vinyloxy-phosphonium species. Under these conditions, we observed the., rapid appearance of three transient intermediates ( 1Pcx+92, +40, and -7.3 ppm), although vinyl phosphate was the almost exclusive final product. The peak at -7.3 ppm disappeared most rapidly, with the simultaneous development of a corresponding peak at -7.2 ppm due to vinyl phosphate, and is tentatively assigned to the vinyloxyphosphonium bromide. Jt is known that tetraalkoxyphosphonium ions have XP chemical shifts which are not far removed from those of the corresponding phosphate esters ( ) ... 

Irradiation of a-bromoacetophenones in methanol yields only ionic products (i.e. nucleophilic substitution and Favorskii-type rearrangement products) if there is an ortho-methoxy substituent in the aromatic ring152. This is due to stabilization of the intermediate cation as a result of interaction between the lone pair on the oxygen of the ortho-methoxy group and the vacant p-orbital of the cation. With an ortho-acetoxy substituent in the ring... 

When a-bromoacetophenone semicarbazone (366) is allowed to react with enamines of cyclic ketones or aldehydes, such as 365 in the presence of triethylamine, substituted... 

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