Dichloro reaction with toluene

An abnormal (tele) substitution of chlorine in both 2,3- and 2,6-dichloropyrazines 91, 92 occurred on reaction with dithiane anion, while morpholine gave the normal //wo-substitution <06TL31>. Another paper described the highly selective ipso monosubstitution of the 2,3-dichloro compound by enolates in toluene <06T9919>. 

The nitration of l,3,5-trichloro-2-nitrobenzene (8) to l,3,5-trichloro-2,4-dinitrobenzene (9) with dinitrogen pentoxide in absolute nitric acid goes to completion in only 2-4 minutes at 32-35 °C. Further nitration of (9) would yield l,3,5-trichloro-2,4,6-trinitrobenzene (10) which undergoes ammonolysis on treatment with ammonia in toluene to give the thermally stable explosive 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) (11). The same sequence of reactions with l,3-dichloro-2-nitrobenzene provides a route to l,3-diamino-2,4,6-trinitrobenzene (DATE). Such reactions are clean and occur in essentially quantitative yield. 

The kinetic instability of the polyhydrofullerenes is shown by the reaction with 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) in refluxing toluene. Thereby, the Birch-Hiickel products completely convert into Cjq, which shows that the hydrogenation is completely reversible (Scheme 5.2) [42]. 

In the tetrahydrofuran compounds there is opportunity for the existence of cis and irans isomers. They have been separated81 in the case of XL and XLII, the cis-form of which forms an anhydride. Evidence for the existence of the cts-form of 2,5-dishydroxymethyltetra-hydrofuran (XXXVIII) is found in the behavior of either its dichloro-or di-toluene-p-sulfonyl derivative with methanolic ammonia. From this reaction the dicyclic compound, 8-oxa-3-aza6fcyeZo [3,2,1] octane (XLIII) is obtained which can have been formed only from the m-form of the dicarbinol.82 An example of the addition of bromine to the furan... 

The successful isolation of the intermediate, 2-ethylpyridinium dichloro-phosphino-ethoxycarbonylmethylide (10) on carrying out the reaction in toluene establishes initiation of the reaction at the /V-mcthylcnc group [21], The reaction of l-benzyl-2-methylpyridinium bromide with PC13 and Et3N, however, commences at the 2-methyl group, as evidenced by the formation of 11 that does not cyclize even on heating [26],... 

Similar reactions occur with toluene (35), which with Cs-K-Na alloy in THF at about -45°C gives 116 which with water yields 46% of 117. Dehydrogenation of 117 with 2,3-dichloro-4,5-dicyanobenzoquinone (DDQ) gives dimethylbiphenyl, which contains more than 99% of 3,3 -dimethylbiphenyl 118. 

Typical procedure. 6-N-Phthaloyl-2 -0-(9-phenylxanthen-9-yl)-5 -0-(fluoren-9-yl-metln-oxycarbonyl)adenosine 865 [628] To a solution of 864 (635 mg, 1 mmol) in dry pyridine (10 mL) was added dropwise a solution of Fmoc-Cl (336 mg, 1.3 mmol) in dry acetonitrile (5 mL). The reaction mixture was stirred for 4.5 h at room temperature and was then poured into cold, saturated sodium hydrogen carbonate solution (100 mL). The resulting mixture was extracted with chloroform (2 x 50 mL), the combined organic layers were concentrated in vacuo, and the residue was dried by co-evaporation with toluene (4 x 25 mL). It was then dissolved in dichloro-methane, and precipitation from cyclohexane gave 865 yield (717 mg, 82%) ... 

Sulphines may react as dienophiles with 1,3-dienes with the formation of cyclic sulphoxides. Unstable 2,2-dichloro-5,6-dihydro-2ff-thiin-l-oxide 191 was formed in an exothermic reaction between 173aandcyclopentadieneat — 40 (equation 101). The simplest, parent sulphine, CH2 = S = O, prepared in situ by treatment of a-trimethylsilylmethanesulphinyl chloride with cesium fluoride, reacts with cyclopentadiene to give bicyclic, unsaturated sulphoxide 192 as a mixture of two diastereoisomers in a 9 1 ratio (equation 102). On the other hand, a,j8-unsaturated sulphine 193 (generated by thermolysis of 2-benzylidene-l-thiotetralone dimer S-oxide) in boiling toluene behaves as a 1,3-diene and was trapped by norborene forming sulphoxide 194 in 78% yield ° (equation 103). 

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