O-Dibromobenzene

The following give abnormal results when treated with chlorosulphonio acid alone, preferably at 50° for 30-60 minutes —fluobenzene (4 4 -difluorodiplienyl-sulphone, m.p. 98°) j iodobenzene (4 4 -di-iododiphenylsulplione, m.p. 202°) o-diclilorobenzene (3 4 3. -4 -tetrachlorodiphenylsulphone, m.p. 176°) and o-dibromobenzene (3 4 3 4 -tetrabromodiphenylsulphone, m.p. 176-177°). The resulting sulphones may be crystallised from glacial acetic acid, benzene or alcohol, and are satisfactory for identification of the original aryl halide. In some cases sulphones accompany the sulphonyl chloride they are readily separated from the final sulphonamide by their insolubility in cold 6N sodium hydroxide solution the sulphonamides dissolve readily and are reprecipitated by 6iV hydrochloric acid. 

In the reaction of o-dibromobenzene, disubstitution is faster than monosubstitution, and the disubstituted product is obtained as a major product. Similarly, 1,2,4,5-tetrabromobenzene reacts with styrene to give the tetrasub-stituted product[29]. The bridged, annulated [2,2]paracyclophanedieiie 22 was... 

As early as 1907, A.V. Braun and J. Tscherniak first obtained phthalocyanine from phthalimide and acetic anhydride [5]. The prepared blue substance, however, was not investigated further. In 1927, de Diesbach and von der Weid, in an attempt to synthesize phthalonitrile from o-dibromobenzene and copper cyanide in pyridine at 200°C, obtained a blue copper complex. The substance was found to be exceptionally fast to acid, alkali, and high temperature [6], Approximately one year later, in trying to manufacture phthalimide from phthalic anhydride and ammo-... 

Scheme 28 Sequential reactions of o-dibromobenzene with two different electrophiles [63]...

Yoshida et al. [63] applied microreaction technology for the sequential synthesis and the disubstitution of o-bromophenyUithiuni (Scheme 28). Lithiation of o-dibromobenzene in batch leads to the formation of the highly reactive benzyne and to the further creation of various side products thus this reaction needs to be conducted at 100°C and below to avoid this problem. This reaction was optimized under microreactor conditions for the production of o-bromophenyUithium and for its further reaction with methanol to determine the yield of bromobenzene. Microreactors were set up of stainless steel tubes with an internal diameter of 250-1,000 pm. 

Nagaki A, Tomida Y, Usutani H et al (2007) Integrated micro flow synthesis based on sequential Br-Li exchange reactions of p-, m-, and o-dibromobenzenes. Chem Asian J 2(12) 1513-1523... 

Treatment of o-dibromobenzene with lithium tributylmagnesate yielded 2-butylphenyl-magnesium reagent, which was formed via benzyne (Scheme 6)". 

The reaction conditions are similar to those described for the monohalides, except that the amount of cobalt is doubled. When X = Br, only the dizinc species is obtained at 4 F per mol with good yields except in the case of o-dibromobenzene, where the yield is poor. Results are reported in Table 9. 

Dinitro-4.3-dibromobenzene, rhmb ndls (from glac acet ac) or crysts (from CS2), readily sublimes by heating on a w bath, mp 114-15° d 2.313 mod sol in eth, chlf CS2 diffc sol in cold ale, petr eth glac acet ac obtd by warming o-dibromobenzene or 1-nitro-3,4-dibromobenzene with mixed acid (Ref 1)... 

The intramolecular Diels-Alder addition of a benzyne to a furan has been exploited in a synthesis of mansonone E (81TL4877). The benzyne (211), generated from the anthranilic acid (210), yields the adduct (212 86%) which is easily converted into the naphthalene (213 Scheme 79). A similar addition was achieved by generating the benzyne by treating an o -dibromobenzene with butyllithium. 

Telluranthrene was obtained in trace amounts (3%) by the reaction of o-dichlorobenzene with sodium telluride (88M13) and in somewhat higher yield (12%) by the reaction of o-diiodobenzene with sodium ditelluride (91 KGS 1203). It is worth nothing that the analogous reaction of o-dibromobenzene with sodium diselenide leads not to selenanthrene but to poly(o-phenylene)diselenide in 26% yield (87IC1664). 

History. Braun and Tschemak [23] obtained phthalocyanine for the first time in 1907 as a byproduct of the preparation of o-cyanobenzamide from phthalimide and acetic anhydride. However, this discovery was of no special interest at the time. In 1927, de Diesbach and von der Weid prepared CuPc in 23 % yield by treating o-dibromobenzene with copper cyanide in pyridine [24], Instead of the colorless dinitriles, they obtained deep blue CuPc and observed the exceptional stability of their product to sulfuric acid, alkalis, and heat. The third observation of a phthalocyanine was made at Scottish Dyes, in 1929 [25], During the preparation of phthalimide from phthalic anhydride and ammonia in an enamel vessel, a greenish blue impurity appeared. Dunsworth and Drescher carried out a preliminary examination of the compound, which was analyzed as an iron complex. It was formed in a chipped region of the enamel with iron from the vessel. Further experiments yielded FePc, CuPc, and NiPc. It was soon realized that these products could be used as pigments or textile colorants. Linstead et al. at the University of London discovered the structure of phthalocyanines and developed improved synthetic methods for several metal phthalocyanines from 1929 to 1934 [1-11]. The important CuPc could not be protected by a patent, because it had been described earlier in the literature [23], Based on Linstead s work the structure of phthalocyanines was confirmed by several physicochemical measurements [26-32], Methods such as X-ray diffraction or electron microscopy verified the planarity of this macrocyclic system. Properties such as polymorphism, absorption spectra, magnetic and catalytic characteristics, oxidation and reduc-... 

Common Name 1,2-Dibromobenzene Synonym o-dibromobenzene Chemical Name 1,2-Dibromobenzene CAS Registry No 583-53-9 Molecular Formula C6H4Br2 Molecular Weight 235.904 Melting Point (°C) ... 

Some evidence for the formation of benzyne in the cathodic reduction of o-dibromobenzene 173 has been obtained ... 

The noninterpenetrated or open square grid polymer with 2 was first observed in the crystal structure of [Cd(2)2(N03)2] 2(o-dibromobenzene) H [13]. The guest molecules were included in the cavities by eschewing the interpenetration of the... 

Figure 3 Inclusion of o-dibromobenzene (space filling mode) in square grid networks of 2 and Cd(N03)2.

Excited radical anions may be created in a medium which is only slightly reducing, which is not always the case in the presence of anions or by direct electrochemistry. If, for instance, o-dibromobenzene is electrochemically reduced, benzene is the product, obtained via bromobenzene radical and benzyne, since the second electron uptake cannot be avoided [181]. 

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