Reactions with Other Nucleophiles

Reactions with other nucleophiles follow a similar mechanism. For the reaction of Cl with poly(3-methylthiophene) in acetonitrile, the reaction stops at structure 5 (Scheme 2).128 A fully conjugated, Cl-substi-tuted product 6 can subsequently be obtained by electrochemical or chemical dehydrogenation.128 With Br and alcohols, the overoxidation... 

The reaction with carboxylates occurs over a range of pH values, but is optimal at pH 5.0. Unfortunately, the diazoalkyl compounds will cross-react with sulfhydryl groups at this pH. At higher pH conditions, the reaction is even less specific due to reaction with other nucleophiles. In aqueous solution, the most-likely side reaction is hydrolysis. 

Cycloaddition Reactions with Other Nucleophiles The anodic two-electron oxidation of catechol affords o-quinone that may react with the enolates of 4-hydroxycoumarine or 5,5-dimethyl-1,3-cyclohexanedione (dimedone). The resulting adducts undergo a second anodic oxidation leading to benzofuran derivatives in good yields (90-95%) (Scheme 53) [75, 76]. 

The scope of allylic electrophiles that react with amines was shown to encompass electron-neutral and electron-rich ciimamyl methyl carbonates, as well as furan-2-yl and alkyl-substituted allylic methyl carbonates. An ort/io-substituted cinnamyl carbonate was found to react with lower enantioselectivity, a trend that has been observed in later studies of reactions with other nucleophiles. The electron-poor p-nitrocinnamyl carbonate also reacted, but with reduced enantioselectivity. Allylic amination of dienyl carbonates also occur in some cases with high selectivity for formation of the product with the amino group at the y-position over the s-position of the pentadienyl unit [66]. Arylamines did not react with allylic carbonates under these conditions. However, they have been shown to react in the presence of the metalacyclic iridium-phosphoramidite catalysts that are discussed in Sect. 4. 

Sec. IV.D] PYRANS, THIOPYRANS, AND SELENOPYRANS 3. Reaction with Other Nucleophiles... 

Reactions with Other Nucleophiles in Aqueous Solution Spiro Adducts. . 433... 

Alcoholysis or reactions with other nucleophiles may also occur in use, and condensation may take place between two silanol molecules [reaction (3)] or between silanol and the solid substrate [reaction (4)]. 

Acyl chloride-functionalized SWCNTs are also susceptible to reactions with other nucleophiles, e.g. alcohols. Haddorfs group reported the preparation of soluble ester-functionalized carbon nanotubes SWCNT-COO(CH2)17CH3 (Fig. 1.6a) obtained by esterification with octadecanol [134]. The syntheses of soluble polymer-bound and dendritic ester-functionalized SWCNTs have been reported by Riggs et al. by attaching poly(vinyl acetate-co-vinyl alcohol) (Fig. 1.6b) [135] and hydrophilic and lipophilic dendron-type benzyl alcohols [119], respectively, to SWCNT-COC1 (Fig. 1.6c). These functional groups could be removed under basic and acidic hydrolysis conditions and thus additional evidence for the nature of the attachment was provided [119, 136]. 

The ease with which the dithiocarbamate intermediates can be prepared prompted further study of their utilization in preparing potential antioxidants by reaction with other nucleophiles. In addition to their reaction with alcohols to produce 3,5-dialkyl-4-hydroxybenzyl alkyl ethers (22) we found that the intermediates react with secondary amines to give 3,5-dialkyl-4-hydroxybenzylamines, XIV, and with primary amines to give bis (3,5-dialky 1-4-hydroxybenzy 1) amines, XV, (19). 

But why are these alkyl iodides made They are needed for reactions with other nucleophiles in which iodide is again displaced. As well as being one of the best nucleophiles for saturated carbon, iodide ion is one of the best leaving groups from saturated carbon (see p. 430). Yields are often higher if the alkyl iodide is prepared than if the eventual nucleophile is reacted directly with the alkyl tosylate or chloride. 

Alkaline hydrolysis of 2-trifluoromethylimidazole to the 2-carboxylic acid occurs at 30 C in O.IM KOH with a half-life of 5.8 hours. The 4-methyl analogue is 12 times more reactive than the parent. The rate-limiting step in the reaction is the solvent-assisted, internal elimination of fluoride ion from the imidazole anion, to give a transient difluoroazafulvene which can be trapped in reaction with other nucleophiles (Scheme 102) (79JOC2902). 

We also observed quantitative reactions with other nucleophiles such as amines and organometallics. 

The elements of H and Nu are added to the carbonyl group. In Chapter 20 you learned about this reaction with hydride (H ) and carbanions (RO as nucleophiles. In Chapter 21. we will discuss similar reactions with other nucleophiles. 

A thioester (RCOSR ) has a good leaving group ( SR ), so, like other acyl compounds, it undergoes substitution reactions with other nucleophiles. 

In 5 nI reactions of aliphatic substrates it is important to note that the electrophile is a carbonium ion and this is much less discriminating towards nucleophiles than are less reactive electrophilic species. In such reactions the nucleophilic strength of azide ion has no direct effect on rates, but is involved in determining product ratios in competitive reactions with other nucleophiles, including the solvent. Concentration factors are therefore important and salt effects of dissolved azides may also be significant -. 

Often, the carboxylic acid groups are converted to acyl chlorides with SOCI2109 110 prior to esterification with various alcohols and reaction with other nucleophiles.111 Both mono- and difunctional ester-substituted bipyridines have been generated in moderate yield by palladium(O)-catalyzed carboalkoxylation of halo- or triflate-substituted precursors in the presence of CO, an alcohol, and a tertiary amine.112... 

Before 1960, only sodamide and potassium amide were used for the a-metallation of nitriles ( CH—C=N) and successful couplings with electrophiles were restricted to alkylations [la]. The extension of the number of base-solvent systems allowed a clean a-metallation of a variety of nitriles and the subsequent successful reaction with other nucleophiles [lb]. The use of a-metallated dialkyl-aminonitriles R2NCH(R )C=N and protected cyanohydrins R CH(C=N)OR (R = SiMe3 or CH(CH3)OEt) as acyl-anion equivalents in organic synthesis has been reviewed by Albright [2]. 

This series gives a good illustration of factors which influence toxicity other than affinity (K ) and reactivity (kp) with AChE. The phosphonylfluorocholines possess high affinity for the enzyme, are very reactive as electrophiles, but are presumably partially detoxified by rapid hydrolysis and reactions with other nucleophiles. 

Quinazoline 3-oxide derivs. s. 16, 503 also reaction with other nucleophiles s. K.-H. Wunsch et al., Z. Chem. 10, 113 (1970)... 

A mixture of ethylene carbonate, anhydrous KF, and diethylene glycol heated until at 160-165° GOg-evolution starts, the temp, raised to 190° during 1 hr., finally distilled helow 100°/30 mm 2-fluoroethanol. Y 55%. F. e. s. I. Shahak and E. D. Bergmann, Ghem. Gomm. 1965, 122 preferably with potassium hydrogen fluoride, and reaction with other nucleophiles, s. Soc. (G) 1966, 899. 

The formation of d-carbyl complexes as an intermediate probably also occurs in reactions with other nucleophiles. 

Reaction with Other Nucleophiles. Electron-rich aromatics can be fluorinated in low to modest yield by heating with N-fluorobenzenesulfonimide without a solvent to about 100-150 °C (eq 9). ... 

Handling, Storage, and Precautions the reagent is not stable for long periods of time and should be prepared as needed. It is subject to hydrolysis and reaction with other nucleophiles such... 

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