With Other Nucleophiles

The allyl aryl sulfones 116, 117, and 118 can be prepared by 1 1 and 1 2 additions of arylsulfinic acid to butadiene[10l,106,107], The reaction of myr-cene (119) with p-tolylsulfmic acid affords the 1 1 adduct 120 as the main 

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STMP reacts with other nucleophiles such as aqueous ammonia to yield amidophosphates, which contains a P—N bond. STMP is used for the modification of the physical properties of starch and proteins by reaction with the amino and hydroxyl groups. 

Krespan ° has prepared a number of macrocycles, having both aza- and oxa-linkages in them, based on the 3,3-dimethyleneoxetane unit (see also Sect. 8.4 and Eq. 8.12). Typically, 3,3-bis(chloromethyl)oxetane is treated with a diol as shown in Eq. (3.40), in the presence of base. Once the bicyclic system is formed, further treatment with other nucleophiles (e.g., ammonia) can lead to opening of the 4-membered ring. 

Reactions of Enamine Salts with Other Nucleophilic Reagents... 

In work on 6-methoxypyrimidines (130), the 4-methylsulfonyl group was found to be displaced by the sulfanilamide anion more readily than were 4-chloro or trimethylammonio groups. This reactivity may be partly due to the nature of the nucleophile (106, Section II, D, 1). However, high reactivity of alkyl- and aryl-sulfonyl heterocycles with other nucleophiles has been observed. A 2-methylsulfonyl group on pyridine was displaced by methoxide ion with alkaline but not acidic methanol. 3,6-Bis(p-tolylsulfonyl)-pyridazine reacts (100°, 5 hr) with sulfanilamide anion and even the... 

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... 

When aromatic nitro compounds are treated with cyanide ion, the nitro group is displaced and a carboxyl group enters with cine substitution (p. 854), always ortho to the displaced group, never meta or para. The scope of this reaction, called the von Richter rearrangement, is variable. As with other nucleophilic aromatic substitutions, the reaction gives best results when electron-withdrawing groups are in ortho and para positions, but yields are low, usually < 20% and never > 50%. 

Another consequence of application of organic solvents as a reaction medium is associated with the mechanism of enzyme-catalyzed transformations. According to the commonly accepted mechanism, the first product of the interaction of a hydrolytic (serine) enzyme with an ester is an O-acylenzyme (Scheme 5.4). When the reaction is performed in an aqueous solution, water acts as a nucleophile in the next step, to give acid B. If more nucleophilic hydrogen peroxide is present in the reaction mixture, peroxycarboxylic acids C are formed. However, in organic solvents the O-acylenzyme also reacts readily with other nucleophiles, such as... 

In the present study the dimer (salen)CoAlX3 showed enhanced activity and enantioselectivity. The catalyst can be synthesized easily by readily commercially available precatalyst Co(salen) in both enantiomeric forms. Potentially, the catalyst may be used on an industrial scale and could be recycled. Currently we are looking for the applicability of the catalyst to asymmetric reaction of terminal and meso epoxides with other nucleophiles and related electrophile-nucleophile reactions. 

While it was felt that some of the individual issues above could be addressed using the same synthetic sequence (e.g., alternate catalysts for the reduction step) it seemed unlikely that all the above would be solvable, especially as efforts to replace sodium azide with other nucleophiles had failed. Based on this assessment the team felt it would be necessary to evaluate a fundamentally new approach to taranabant and, in particular, to look for a method for installation of the chiral centers without the intermediacy of an alcohol. 

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]. 

As shown in Figure 4.1, the initial step of the conversion of an ylide into a carbene complex is an electrophilic attack at the ylide. Reactions of this type will, therefore, occur more readily with increasing nucleophilicity of the ylide and increasing electrophilicity of the metal complex L M. Complexes which efficiently catalyze the decomposition of even weakly nucleophilic ylides can easily react with other nucleophiles also, such as amines or thiols. This has to be taken into account if reactions with substrates containing such strongly nucleophilic functional groups are to be performed. 

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. 

Benzotriazine (8, R = H), for example, can be isolated as a reasonably stable, colorless crystalline solid, but it reacts rapidly in solution with water to give o-aminobenzaldehyde, presumably by initial covalent hydration to give 98, which decomposes to o-aminobenzaldehyde via the triazene 99. Reaction of 8, R = H, with other nucleophiles also occurs readily, while 4-substituted 1,2,3-benzo-triazines react similarly but more slowly, as expected, owing to a combination of steric and electronic effects. 

Although difluoroenoxysilanes are typical nucleophiles, they can also react with other nucleophiles via their oxidation into radical cations. The oxidative homocoupling and the cross-coupling with heteroaromatics and alcohols proceeds very well in the presence of Cu triflate as the oxidizing reagent (Figure 2.24). " ... 

Reduced pyrimidines by adduct formation with other nucleophiles... 

The electrophilic reaction of magnesium alkylidene carbenoids with other nucleophiles than the original Grignard reagent can also be carried out. For example, treatment of magnesium alkylidene carbenoid 157, derived from 147, with a-sulfonyl lithium carbanion afforded allenes 159 in moderated yields (equation 39/. ... 

Treatment of (185) with other nucleophiles, e.g. sodium methoxide or the anion of nitromethane (68CRV747, p. 752, 76JHC433), also induces ring expansion and treatment with hydroxide gives the 2-oxo derivative (188) (68CRV747, p. 755,67JOC2417) via the oxime (187)... 

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