O-alkylating agent

This is a versatile reaction because one may use different attacking carbanionic groups (RLi, R = alkyl, aryl, or silyl) and different O-alkylating agents. Carbonyl complexes of several different metals, such as Mo, Mn, Rh, Fe, and Ni, undergo this transformation. 

Example 1, The Meerwein reagent is an excellent O-alkylating agent ... 

Manufacture of alkylsulfones, important intermediates for metal-complex dyes and for reactive dyes, also depends on O-alkylation. An arylsulphinic acid in an aqueous alkaline medium is treated with an alkylating agent, eg, alkyl haUde or sulfate, by a procedure similar to that used for phenols. In the special case of P-hydroxyethylsulfones (precursors to vinylsulfone reactive dyes) the alkylating agent is ethylene oxide or ethylene chlorohydrin. 

The methylation of N-methyl derivatives of maleic hydrazide gives in general O-alkylated products. The opposite results are obtained with benzyl halides as alkylating agents. In this case the O-benzyl derivative (71) is formed, which is then further benzylated to the lV,0-dibenzyl derivative (72). When ethyl chloroacetate is used, the direction of alkylation is dependent on pH. At pH above 8, O-alkylation occurs at pH below 8, N-alkylation takes place exclusively in neutral and acidic solutions only IV-alkylated products are formed. 

The trend in relative effectiveness of RAFT agents with varying Z is rationalized in terms of interaction of Z with the C=S double bond to activate or deactivate that group towards free radical addition. Substituents that facilitate addition generally retard fragmentation. O-Alkyl xanthates (Z=0-alkyl, Table... 

Alkylation reactions. In a laboratory procedure for the alkylation of benzene with benzyl chloride using the catalyst EPZIO at room temperature 100% conversion of the alkylating agent in less than 15 minutes was obtained (Envirocats, 1990). EPZE was efficiently used in the sulphonation of o-xylene with benzenesulphonyl chloride to give 3,4-... 

This chapter compares the reaction of gas-phase methylation of phenol with methanol in basic and in acid catalysis, with the aim of investigating how the transformations occurring on methanol affect the catalytic performance and the reaction mechanism. It is proposed that with the basic catalyst, Mg/Fe/0, the tme alkylating agent is formaldehyde, obtained by dehydrogenation of methanol. Formaldehyde reacts with phenol to yield salicyl alcohol, which rapidly dehydrogenates to salicyladehyde. The latter was isolated in tests made by feeding directly a formalin/phenol aqueous solution. Salicylaldehyde then transforms to o-cresol, the main product of the basic-catalyzed methylation of phenol, likely by means of an intramolecular H-transfer with formaldehyde. With an acid catalyst, H-mordenite, the main products were anisole and cresols moreover, methanol was transformed to alkylaromatics. 

Neutral tertiary and secondary amides react with very reactive alkylating agents, such as triethyloxonium tetrafluoroborate, to give O-alkylation.63 The same reaction occurs, but more slowly, with tosylates and dimethyl sulfate. Neutralization of the resulting salt provides iminoethers. 

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 methano-dimer of a-tocopherol (28)50 was formed by the reaction of o-QM 3 as an alkylating agent toward excess y-tocopherol. It is also the reduction product of the furano-spiro dimer 29, which by analogy to spiro dimer 9 occurred as two interconvertible diastereomers,28 see Fig. 6.23. However, the interconversion rate was found to be slower than in the case of spiro dimer 9. While the reduction of furano-spiro dimer 29 to methano-dimer 28 proceeded largely quantitatively and independently of the reductant, the products of the reverse reaction, oxidation of 28 to 29, depended on oxidant and reaction conditions, so that those two compounds do not constitute a reversible redox pair in contrast to 9 and 12. 

Monoanions derived from nitroalkanes are more prone to alkylate on oxygen rather than on carbon in reactions with alkyl halides, as discussed in Section 5.1. Methods to circumvent O-alkylation of nitro compounds are presented in Sections 5.1 and 5.4, in which alkylation of the a.a-dianions of primary nitro compounds and radial reactions are described. Palladium-catalyzed alkylation of nitro compounds offers another useful method for C-alkylation of nitro compounds. Tsuj i and Trost have developed the carbon-carbon bond forming reactions using 7t-allyl Pd complexes. Various nucleophiles such as the anions derived from diethyl malonate or ethyl acetoacetate are employed for this transformation, as shown in Scheme 5.7. This process is now one of the most important tools for synthesis of complex compounds.6811-1 Nitro compounds can participate in palladium-catalyzed alkylation, both as alkylating agents (see Section 7.1.2) and nucleophiles. This section summarizes the C-alkylation of nitro compounds using transition metals. 

Reactions of trident and ambident anions of hydroxy compounds with alkylating reagents were also studied.121 The ion-pair extraction method was found to be superior alkylating agents were methyl iodide (soft) and dimethyl sulfate (hard). Upon alkylation by ion-pair extraction the 5-methyl-substituted selenolene-2-one system gives mainly C-alkylation with the soft acid, methyl iodide, and mainly O-alkylation with the hard acid, dimethyl sulfate. 

Reaction of (66) with the difunctional alkylating agent, a,a-dibromo-o-xylene, results in ring closure to produce (67) by bridging the c/s-thiolato functions of (66) as shown in [2.10] (Thompson Busch, 1964). This... 

Diazo compounds and oxonium salts are the most efficient alkylating agents in the synthesis of alkyl nitronates. It is assumed that diazo compounds are inserted into the O-H bond in the aci forms of the corresponding AN, whereas oxonium salts generally react with AN anions. 

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