Sulfones, alkylation acylation

Know the meaning of electrophilic aromatic substitution, halogenation, nitration, sulfonation, alkylation, acylation, Friedel-Crafts reaction. 

A-Alkylation, -acylation and -sulfonation are also promoted by a polar solvent, such as HMPA (hexamethylphosphoric triamide).This acts to solvate the ions (promoting dissociation), but in a non-polar solvent like diethyl ether or tetrahydrofuran (THF), attack by most carbon electrophiles upon indolylmagnesium bromide proceeds at C-3 (Scheme 7.9). 

Aromatic compounds react mainly by electrophilic aromatic substitution, in which one or more ring hydrogens are replaced by various electrophiles. Typical reactions are chlorination, bromination, nitration, sulfonation, alkylation, and acylation (the last two are Friedel-Crafts reactions). The mechanism involves two steps addition of the electrophile to a ring carbon, to produce an intermediate benzenonium ion, followed by proton loss to again achieve the (now substituted) aromatic system. 

R = alkyl, aryl R = 1° or 2 alkyl, allyl, benzyl, activated aryl, acyl X - Cl, Br, I, OTs electrophile epoxide, dialkyl sulfate, alkyl sulfonate, alkyl nitrate base = NaOR NaH base = KOf-Bu, cone. NaOEt, NaH solvent = R OH, f-BuOH, benzene, ether, DMF... 

Chemical derivatizations during SFE, for example, to convert carboxyl, sulfonic acid, and amino moieties to their alkyl, acyl, and silyl derivatives are described in Ref. 74. Such analyte derivatizations may be necessary to improve analyte solubility in the extraction fluid, to overcome analyte interactions with the sample matrix, or to facilitate subsequent analysis. This topic will be described in detail in Section II.D. 

Like benzene, substituted benzenes undergo the five electrophilic aromatic substitution reactions discussed in Chapter 15 and listed in Section 16.2 halogenation, nitration, sulfonation, alkylation, and acylation. Now we need to find out whether a substituted benzene is more reactive or less reactive than benzene itself. The answer... 

Alkylation, acylation, sulfonation and silylation occur on the N-atoms of imidazoles [116]. Other reagents substitute onto the C-atoms 4 and 5, which are equivalent as a result of annular tautomerism. 

Systems with a pyrrole-like N-atom can be alkylated, acylated, sulfonated and silylated. Subsequent conversion into quaternary compounds is possible. 

Cg-Cif, acyl monoglyceride sulfonates alkyl chain length Macherey Nagel Nucleosil Ci, 4 X 250 mm MeOH/HzO, 90 10 or 80 20, containing 0.25 M NaC104 RI 8... 

Alkyl halides and sulfonates are the most frequently used alkylating acceptor synthons. The carbonyl group is used as the classical a -synthon. O-Silylated hemithioacetals (T.H. Chan, 1976) and fomic acid orthoesters are examples for less common a -synthons. In most synthetic reactions carbon atoms with a partial positive charge (= positively polarized carbon) are involved. More reactive, "free carbocations as occurring in Friedel-Crafts type alkylations and acylations are of comparably limited synthetic value, because they tend to react non-selectively. 

Fluorosulfuric acid [7789-21-17, HSO F, is a colodess-to-light yellow liquid that fumes strongly in moist air and has a sharp odor. It may be regarded as a mixed anhydride of sulfuric and hydrofluoric acids. Fluorosulfuric acid was first identified and characterized in 1892 (1). It is a strong acid and is employed as a catalyst and chemical reagent in a number of chemical processes, such as alkylation (qv), acylation, polymerization, sulfonation, isomerization, and production of organic fluorosulfates (see Friedel-CRAFTSreactions). 

Sulfonated styrene—divinylbensene cross-linked polymers have been appHed in many of the previously mentioned reactions and also in the acylation of thiophene with acetic anhydride and acetyl chloride (209). Resins of this type (Dowex 50, Amherljte IR-112, and Permutit Q) are particularly effective catalysts in the alkylation of phenols with olefins (such as propylene, isobutylene, diisobutylene), alkyl haUdes, and alcohols (210) (see Ion exchange). Superacids. 

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