S jAr reaction

Studies of the S Ar mechanism have involved theuse of 2,4-dmitrofluoroben-zene as a substrate The S, jAr reaction of fluoroaromatics is catalyzed by both aromatic and alphatic amines [42. 43 44, 45, 46 47, 48, 49] Diamines [50] and... 

Scheme 51 Synthesis of carbazoles 218 by tandem Suzuki-Miyaura cross-coupling and S jAr-reaction...

Another S jAr reaction heats benzenesulfonic acid (42) with aqueous sodium hydroxide (to 300°C) in a reaction bomb. The fastest reaction is the deprotonation of the acid by hydroxide to give sodium benzenesulfonate (152), an acid-base reaction with the acidic phenol 152 reacts with hydroxide to give the resonance-stabilized carbanionic intermediate, 153. Loss of sodium sulfite (Na2S03) gives phenoxide, 154. Cooling the reaction and neutralization with acid give phenol, 19. 

Ferrocenyhnethylamine 52, which is commercially available, gives 2-dimethyl-aminomethyl formyl ferrocene by metallation and formylation. This aldehyde 53 is converted to an oxime, then reduced to a primary amine 54. An S jAr reaction between this amine and 4,7-dichloroquinoline yields the expected ferroquine 45 in the form of a yellow solid. Finally, the free base 45 is converted by L(+) tartaric acid or H Cl to the salt 5 5 which is water-soluble and thus more convenient for use. 

The S,jAr reaction is circumscribed by the major mechanisms of nucleophilic aromatic substitution the most common S, Ar addition-ehmination (Chapter 6), the oxidative nucleophilic aromatic substitution of hydrogen (ONSH Chapter 11), the benzyne mechanism (Chapter 12), and the radical-nucleophilic aromatic substitution Sj j l (Chapter 10). The chiral inductor can be bonded (Section 8.2) or nonbonded to the reactants (Section 8.3) (Scheme 8.1). 

There is no clear-cut proof that a one-step Sn2 mechanism, so important at a saturated carbon, ever actually occurs with an aromatic substrate. The hypothetical aromatic Sn2 process is sometimes called the one-stage mechanism to distinguish it from the two-stage S jAr mechanism. A clean example of a Srn2 reaction has been reported, the conversion of 10 to 11 in methanol.Both the SrnI and Srn2 reactions have been reviewed. ... 

As base. Many reactions that are promoted by a base can be effected with KF/AljO, for example, in deprotonating malononitrile for Michael reaction, in N-pyridylation of indole which is based on the S,.jAr mechanism, and in the preparation of a-heterosubstituted Weinreb amides from 7V-methoxy-A(-methyl chloroacetamide. ... 

A seemingly simple reaction is the rapid conversion by amide ion in ammonia of 2-halo-4-phenylpyrimidines to the corresponding 2-amino compound in high yield, Eq. (8), R = H. A straightforward interpretation of this result employs an S jAr mechanism in which amide ion adds to position 2, the center bearing the halogen... 

In the absence of methoxide ion substitution takes place at a slower rate by an S jAr route. Formerly, the presence of methoxide ion in substitution reactions involving thiolate ions in methanol was avoided studiously in order to prevent a competing substitution by the methoxide ion. Although methoxide ion is required for the radical chain process to occur, only traces of substitution product containing the methoxy group are present, demonstrating that benzenethiolate ion is superior to methoxide ion in trapping the intermediate 4-isoquinolyl radical,116 Scheme 12. 

Instead of rotational force, which, of course, is everybody s first reaction to the problem of getting a lid off a jar. 

VNS hydroxylation of nitroarenes with alkylhydroperoxides proceeds according to mechanism similar to that of the reaction with a-halocarbanions— reversible nucleophiUc addition, followed by the base-induced p-ehmination of alcohols from the intermediate a"-adducts. These mechanistic features were established by detramination of effects of base on the rate of the reaction, namely, on the competition between VNS hydroxylation and S Ar of chlorine in 4-chloronitrobenzene and 2,4-dinitrochlorobenzene. For instance, the reaction of these hydropaoxides with 2,4-dinitrochlorobenzene carried out in the presence of an excess of f-BuOK proceeds exclusively as VNS to give 2,4-dinitro-5-chlorophenol, whereas in the presence of equimolar amount of f-BuOK substantial quantity of 2,4-dinitrophenol, product of S,.jAr is formed (Scheme 11.43) [66]. 

In a 4-I. wide-mouthed glass jar, fitted with a mechanical stirrer, is placed a solution of 150 g. (3 moles) of sodium cyanide (Note i) in 500 cc. of water and 318 g. (3 moles) of u.s.P. benz-aldehyde. The stirrer is started and 850 cc. of a saturated solution of sodium bisulfite (Note 2) is added to the mixture, slowly at first and then in a thm stream. The time of addition is ten to fifteen minutes. During the addition of the first half of this solution, 900 g. of cracked ice is added to the reaction mixture, a handful at a time. The layer of mandelonitrile which appears during the addition of the sulfite solution is separated from the water in a separatory funnel. The water is extracted once with about 150 cc. of benzene, the benzene is evaporated, and the residual mandelonitrile is added to the main portion. 

General. Toluene, chlorobenzene, and o-dichlorobenzene were distilled from calcium hydride prior to use. 4-Dimethylaminopyridine (Aldrich Chemical Co) was recrystalled (EtOAc), and the other 4-dialkylaminopyridines were distilled prior to use. PEG S, PEGM s, PVP s, and crown ethers were obtained from Aldrich Chemical Co., and were used without purification. BuJ r and BU. PBr were recrystallized (toluene). A Varian 3700 VrC interfaced with a Spectraphysics SP-4000 data system was used for VPC analyses. A Dupont Instruments Model 850 HPLC (also interfaced with the SP-4000) was used for LC analyses. All products of nucleophilic aromatic substitution were identified by comparison to authentic material prepared from reaction in DMF or DMAc. Alkali phenolates or thiol ates were pre-formed via reaction of aqueous NaOH or KOH and the requisite phenol or thiophenol in water under nitrogen, followed by azeotropic removal of water with toluene. The salts were transferred to jars under nitrogen, and were dried at 120 under vacuum for 20 hr, and were stored and handled in a nitrogen dry box. 

Many decades ago, Griffith (1919,1920) described the white (laboratory) rat s response to cats. From the age of 3 weeks, rats huddle in corners, freeze, and crouch when presented with a cat. They tremble, twitch their muscles, whine, and cease to feed and nurse. A cloth with cat scent or an arena with cat scent sufficed to trigger these responses. Anosmic rats or those confronted with a cat in a glass jar remained unaffected. Hence, the critical cue proved to be odor (Griffith, 1919). Cat feces, urine, heart, or other tissues did not elicit these fright reactions (Griffith, 1920). 

Reaction to Ammonium Ion (Nessler s Reagent). Introduce 5 ml of a 0.1 N mercury(II) nitrate solution heated to 80 °C into a 50-ml beaker and add 5 ml of a 0.1 A potassium iodide solution. Cool the mixture, let the precipitate settle, pour off the solution, and wash the precipitate three times with cold water by decantation. Add 0.2 g of potassium iodide dissolved in 5 ml of water to the precipitate. When the latter dissolves, pour in 3 ml of a 10% sodium hydroxide solution and transfer the contents into a dark jar. 

Chandelon s method [60] is more widely used. Here 1 part by weight of mercury is dissolved in 10 parts of nitric acid (65% HN03, s.g. 1.40) by moderate heating the solution, heated to 55%, is poured into a flask or retort with a capacity at least 6 times that of the liquid, containing, apart from the above mentioned solution, 8.3 parts of 87% alcohol. The reactor is connected by a vent pipe with stoneware jars and a cooling tower in which the vapours evolved during the reaction are condensed. 

RAJ O FIair, MA Freitas, S Gronert, JAR Schmidt, TD Williams. Concerning the regioselectivity of gas phase reactions of glycine with electrophiles the cases of the dimethylchlorinium ion and the methoxymethyl cation. J Org Chem 60 1990-1998, 1995. 

The slides are first washed, shaken to drain all excess buffer and the substrate solution is pipetted directly onto the slides. If the substrate solution is cloudy, it is preferable to filter it directly onto the slide. Staining is complete after 10-15 min and can be followed under the microscope. The reaction is stopped by washing in a jar with isotonic buffer and extensive rinsing under tap water. The slides should be mounted in aqueous material, such as Apathy s mountant. 

Nicoll JAR, Love S, Burton PA, et al. Autopsy findings in two cases of neonatal herpes simplex virus infection detection of virus by immunohistochemistry, in situ hybridization and the polymerase chain reaction. Histopathology. 1994 24 257-264. 

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