Bromo anionic

Dehydrobenzene or benzyne 158 can be trapped by all manner of species. 1,2-Dehydro-o-carborane 159 has been shown to undergo many of the same reactions as its two-dimensional relative, 1,2-dehydrobenzene. Although dehydroaromatic molecules can be formed in a variety of ways, synthetic pathways to 1,2-dehydro-o-carborane are quite limited. An effective procedure reported so far78 first forms the dianion by deprotonation of o-carborane with 2 equiv. of butyllithium. Precipitated dilithium carborane is then treated with 1 equiv. of bromine at 0°C to form the soluble bromo anion 160. Thermolysis of 160 with anthracene, furan, and thiophene as substrates leads to the adducts 161-164.79 80 1,2-Dehydro-o-carborane reacts with norbomadiene to give both homo 2+4 and 2+2 addition, leading to three products 165-167, in a 7 1 ratio79. An acyclic diene, 2,3-dimethyl-... 

Salts of chloro and bromo anions of Pav can be made by interaction of PaX5 with MX in solvents such as SOCl2 or CH3CN.30... 

Ai-alkyl-iV-nitrosohydroxylaminato, 623 amido, 608 structure, 608 synthesis, 608 amidooxo, 634 amidopentahalo, 595 arsenato, 638 axametallacycles, 611 azido, 619 bromo anionic, 593 bromooxo, 625 carboxylatohalo, 606 carboxylatooxo, 633 chloro anionic, 593 chlorooxo, 625 chloroperoxo, 636 cyano, 623... 

The bis(fluorosulphato)bromate(i) in the form of its Cs+ salt had been reported previously. A more recent investigation by Johnson and Cady has shown that this anion can be generated when MSO3F (M = Li, Na, K, Rb, or Cs) is dissolved in excess BrS03F. Surprisingly, the Li+ and Na+ salts of the bromo-anion could be isolated from solution but not the K+ and Rb+ salts nevertheless, vapour-pressure measurements showed the Cs+ salt to be more stable than the Li+ salt. 

A classical reaction leading to 1,4-difunctional compounds is the nucleophilic substitution of the bromine of cf-bromo carbonyl compounds (a -synthons) with enolate type anions (d -synthons). Regio- and stereoselectivities, which can be achieved by an appropiate choice of the enol component, are similar to those described in the previous section. Just one example of a highly functionalized product (W.L. Meyer, 1963) is given. 

The alkyl halide m this case 2 bromo 2 methylbutane ionizes to a carbocation and a halide anion by a heterolytic cleavage of the carbon-halogen bond Like the dissoci ation of an aUcyloxonmm ion to a carbocation this step is rate determining Because the rate determining step is ummolecular—it involves only the alkyl halide and not the base—It is a type of El mechanism... 

Tertiary alkyl halides are so sterically hindered to nucleophilic attack that the pres ence of any anionic Lewis base favors elimination Usually substitution predominates over elimination m tertiary alkyl halides only when anionic Lewis bases are absent In the solvolysis of the tertiary bromide 2 bromo 2 methylbutane for example the ratio of substitution to elimination is 64 36 m pure ethanol but falls to 1 99 m the presence of 2 M sodium ethoxide... 

The addition of the anion of a-bromo-a-nitrotoluerie (564) to cyclohexene gave the hexahydro derivative (565) of 3-phenyl-l,2-benzisoxazole (75TL2131). An unusual hexahydro derivative (566) was produced by the bis addition of benzonitrile N-oxide to benzoquinone (67AHC(8)277). 

Bromination of the enolate anion from the reaction of 3j -acetoxypregna-5,16-dien-20-one (1) with methylmagnesium bromide in the presence of cuprous chloride affords (after treatment with sodium iodide to dehalo-genate any 5,6-dibromide) a mixture of 17a-bromo- and 17)5-bromo-16a-methyl compounds (11) and (12) in a ratio 9 1. The 17a-iodides can be obtained in an analogous reaction. 

Chloro-l-methyl-2-quinoxalinone (215), which cannot anionize, reacts readUy with iV -methylaniline. 6-Bromo-as-triazine-3,5-dione (216) is largely anionized by dimethylamine but not by thiourea... 

Substituents in the 6-position (cf. 267) show appreciable reactivity. 6-Bromo-as-triazine-3,5(2j, 4j )-dione (316) undergoes 6-substitution with secondary amines or hydrazine, with mercaptide anions or thiourea (78°, 16 hr), with molten ammonium acetate (170°, 24 hr, 53% yield), and with chloride ion during phosphorous oxychloride treatment to form 3,5,6-trichloro-as-triazine. The latter was characterized as the chloro analog of 316 by treatment with methanol (20°, heat evolution) and hydrolysis (neutral or acid) to the dioxo compound. The mercapto substituent in 6-mercapto-as-triazine-3,5(2iI,4if)-dione is displaced by secondary... 

When methylene chloride was used as a solvent, it was found that 28 are obtained in minor amounts, while the dominating product is the -coordinated chloro-carbyne species [(> -Tp )Mo(CO)2(=CCl)], whose yield increases abruptly with substitution in the pyrazol-l-yl fragments (3-methyl-, 3,4,5-trimethyl-, and 3,5-dimethyl-4-chloro derivatives) [90AX(C)59,95JCS(D) 1709]. The tungsten analog can be prepared similarly. The chlorocarbyne molybdenum complex follows also from the reaction of the parent anion with triphenylsulfonium cation but conducted in dichloromethane. The bromo- and iodocarbyne derivatives are made similarly. 

Hydrazinopyridazines such as hydralazine have a venerable history as anti hypertensive agents. It is of note that this biological activity is maintained in the face of major modifications in the heterocyclic nucleus. The key intermediate keto ester in principle can be obtained by alkylation of the anion of pi peri done 44 with ethyl bromo-acetate. The cyclic acylhydrazone formed on reaction with hydrazine (46) is then oxidized to give the aromatized compound 47. The hydroxyl group is then transformed to chloro by treatment with phosphorus oxychloride (48). Displacement of halogen with hydrazine leads to the formation of endralazine (49). ... 

Polystyrene bisperoxides can be prepared by the termination of polystyryl anion with bromo methyl benzoyl peroxide [9] ... 

Indeno[l,2-rf]azepin-4-ol and its 10-bromo derivative appear to be in the lactam form 20. In base solution, however, there is UV and HNMR spectroscopic evidence for the 14k fully conjugated anions, e.g. 21.57... 

With hydrobromic acid and potassium bromate 7-methylxanthine (159 X = H) gave the 2-bromo derivative (159 X = Br) in 83% yield (84CHE924). Conversion of a variety of 2-substituted-6-trifluoromethyl-purines into the anions, followed by treatment with NBS in hot dimethyl-formamide, gave 20-60% yields of 2-bromo derivatives (90JHC1505). 

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