And sulfur nucleophiles

Displacement Reactions with Carbon, O.xygen. and Sulfur Nucleophiles... 

This addition is general, extending to nitrogen, oxygen, carbon, and sulfur nucleophiles. This reactivity of the quinone methide (23) is appHed in the synthesis of a variety of stabili2ers for plastics. The presence of two tert-huty groups ortho to the hydroxyl group, is the stmctural feature responsible for the antioxidant activity that these molecules exhibit (see Antioxidants). 

B. Reactions with Oxygen and Sulfur Nucleophiles 1. Hydrolysis... 

Di Valentin, C. Freccero, M. Zanaletti, C. Sarzi-Amade, M. o-Quinone methide as alkylating agent of nitrogen, oxygen, and sulfur nucleophiles. The role of H-bonding and solvent effects on the reactivity through a DFT computational study, j. Am. Chem. Soc. 2001, 123, 8366-8377. 

The toxicity of 3-methylindole has been attributed to methyleneindolenine trapping of nitrogen and sulfur nucleophiles.57 60-62 Likewise, the ene-imine shown in Scheme 7.9 readily reacted with hydroquinone nucleophiles, resulting in head-to-tail products. Shown in Fig. 7.6 is the 13C-NMR spectrum of a 13C-labeled ene-imine generated by reductive activation. The presence of the methylene center of the ene-imine is apparent at 98 ppm, along with starting material at 58 ppm and an internal redox reaction product at 18 ppm. Thus, the reactive ene-imine actually builds up in solution and can be used as a synthetic reagent. 

Compound 874, as a representative of derivatives with an electron-withdrawing substituent at C-[1 of the vinyl group, is easily prepared by elimination of one benzotriazole from 2,2-/fo(benzotriazol-l-yl)ethyl methyl ketone 873. The stereoselective elimination catalyzed by NaOH gives exclusively the (E) isomer of derivative 874. Addition of nucleophiles to the double bond of vinyl ketone 874 followed by elimination of benzotriazole leads to a,P unsaturated ketones 875. Amines used as nucleophiles do not need any catalysis, but reactions with carbon and sulfur nucleophiles require addition of a base. The total effect is nucleophilic substitution of the benzotriazolyl group at the i-carbon of orji-iinsaturatcd ketone (Scheme 142) <1996SC3773>. 

The benzo[fc]thiophene sulfoxides, such as (142), generated from the parent benzo-thiophene on the H202-TFA-mediated oxidation, undergoes Michael-type nucleophilic addition of oxygen and sulfur nucleophiles in acidic media to produce 3-substituted benzo[fc]thiophenes (143). This method provides an easy two-step functionalization of 2-acylbenzo[fc]thiophene derivatives. ... 

An unexpected endo selectivity in addition of certain carbon and sulfur nucleophiles to the O, / -unsaturated (arene)ruthenium(II)cyclopentadienyl compound (154) has been reported. This stereochemistry has been compared with that of the 5 n2 reactions but a detailed theoretical approach is yet to be undertaken. ... 

The effect which amino functionality has on the thermal and impact sensitivity of polyni-troarylenes (Section 4.8.1.4) makes amination by VNS a method with much future potential for energetic materials synthesis. Other carbon, nitrogen, oxygen and sulfur nucleophiles can displace aromatic hydrogen examples with 1,3-dinitrobenzene and 1,3,5-trinitrobenzene are extensive. 

The chlorine atom in l-(a-chloroalkyl)benzotriazole is readily replaced by a wide range of carbon, nitrogen, phosphorus, oxygen, and sulfur nucleophiles, for example, 1-chloromethylbenzotriazole... 

Reactions with carbon, nitrogen and sulfur nucleophiles 214 Direct observation of nitrenium ions acid-base chemistry and singlet-triplet chemistry 227 Heteroarylnitrenium ions 238 Calculations 244... 

REACTIONS WITH CARBON. NITROGEN AND SULFUR NUCLEOPHILES... 

Our understanding of the chemistry of N-arylnitrenium ions is significantly more advanced than it was a decade ago. Nevertheless, this field of research is still considerably less developed than that of carbenium ions, carbenes, or nitrenes. For example, although singlet nitrenium ions behave as one might expect that their 4-imino-2,5-cyclohexadienyl resonance contributors would in their reactions with H2O, NJ, or Cl, their reactions with carbon, nitrogen, and sulfur nucleophiles, particularly d-G, are not so easily rationalized. Except for d-G, these reactions with soft nucleophiles have not been examined systematically and the regiochemistry exhibited by these nucleophiles is incompletely understood. 

Not all nucleophilic displacement reactions require lightly substituted onium ion catalysts for activity. For alkylation of 2-naphthoxide ion with benzyl bromide (Eq. (6)) 40-100% RS, 2% CL polystyrene catalysts 15 and 16 work well54). A 51 % RS catalyst 11 gave good yields in reactions of anionic oxygen and sulfur nucleophiles with alkyl halides 91). 

Nucleophilic Attack at Ring Atoms 5.16.3.5.1 Oxygen, nitrogen and sulfur nucleophiles... 

Intramolecular conjugate addition occurs in the /3-sulfonylstyrenes (196) (72BCJ1893) and (197) (74JMC549) to give 1,2,4-thiadiazines. In the case of (197), subsequent elimination of HBr gave the fully unsaturated system. Similar intramolecular conjugate addition of oxygen and sulfur nucleophiles to sulfonylstyrenes and sulfonylalkynes also occurs. 

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