Other Nucleophiles

Some nucleophiles other than carbon nucleophiles are allylated. Amines are good nucleophiles. Diethylamine is allylated with allyl alcohol[7]. Allylammes are formed by the reaction of allyl alcohol with ammonia by using dppb as a ligand. Di- and triallylamines are produced commercially from allyl alcohol and ammonia[l74]. 

This kind of chemical reactivity of epoxides is rather general Nucleophiles other than Gng nard reagents react with epoxides and epoxides more elaborate than ethylene oxide may be used All these features of epoxide chemistry will be discussed m Sections 16 11-16 13... 

Nucleophiles other than Gngnard reagents also open epoxide rings These reac tions are carried out in two different ways The first (Section 16 12) involves anionic nucleophiles in neutral or basic solution... 

Nucleophiles other than water can also add to the carbon-nitrogen triple bond of nitriles In the following section we will see a synthetic application of such a nude ophilic addition... 

In forcing conditions with excess of reagents the 5,8-bis derivative was obtained in the above cases, with hydrazine and with sulfur nucleophiles. Other authors have also observed selective reactions in the pyrido[2,3-[Pg.242]

One can extend the strategy employed in the Reissert-Henze reaction to nucleophiles other than cyanide. Phosphorus-based systems were employed in the... 

Because sodium sulfide is a strong nucleophile, other non nucleophilic reagents such as... 

Ring opening of epoxides with nucleophiles other than water (Cl, BrT I, NOz , CN ) can also be catalyzed by halohydrin dehalogenase enzymes (EC 3.8.1.5, also named haloalkane dehalogenase or haloalcohd dehalogenase) (Figure 6.74) [197]. 

Steric reasons for differences between singly and doubly substituted amino derivatives can presumably be ruled out since it has been shown that nucleophiles other than OHe, such as Fe, N , and pyridine, react comparably fast with 192c and bis(dimethylamino)phosphoryl chloride131). 

Because sodium sulfide is a strong nucleophile, other non nucleophilic reagents such as Ca/Hg 144 or Bu3SnH145 are more suitable than Na2S in the synthesis of functionalized olefins (see Eq. 7.105). NaTeH is also effective to induce the elimination reaction presented in Eqs. 7.103 and 7.104.146... 

Various nucleophiles other than methanol can be introduced onto the carbonyl carbon. Anodic oxidation of acylsilanes in the presence of allyl alcohol, 2-methyl-2-propanol, water, and methyl /V-methylcarbamate in dichlorometh-ane affords the corresponding esters, carboxylic acid, and amide derivatives (Scheme 24) [16]. Therefore, anodic oxidation provides a useful method for the synthesis of esters and amides under neutral conditions. 

In attempts to improve the yields of problematic glycosylation reactions, it has become clear that the mechanism is much more complex than Scheme 3.5 suggests. In essence, the oxycarbenium ion(V) is susceptible to attack by nucleophiles other than the glycosyl acceptor (Scheme 3.6). Two intermediates for which there is experimental evidence are glycosyl triflates(VII)17 and glycosyl sulfenates(IX).18... 

This CO insertion occurs under the influence of nucleophiles other than carbon monoxide, e.g., triphenylphosphine. The independence of the rate on the concentration of ligand suggests (52) a rate-controlling dissociation of the octahedral complex assisted by a nucleophilic (ether) solvent. 

The ability of metal ions to accelerate the hydrolysis of a variety of linkages has been a subject of sustained interest. If the hydrolyzed substrate remains attached to the metal, the reaction becomes stoichiometric and is termed metal-ion promoted. If the hydrolyzed product does not bind to the metal ion, the latter is free to continue its action and play a catalytic role. The modus operandi of these effects is undoubtedly as a result of metal-complex formation, and this has been demonstrated for both labile and inert metal systems. Reactions of nucleophiles other than HjO and OH will also be considered. 

Julid and Colonna showed that, as expected, poly-(L)-leucine and poly-(i)-isoleucine could be employed in place of poly-(L)-alanine, while poly-(L)-valine gave poorer results in terms of yields and stereoselectivity [13]. Some other eno-nes were tried without success and nucleophiles other than peroxide anion were... 

In a similar fashion to those results obtained for the oxidation process, on switching from poly-(L)-leucine to poly-(D)-leucine the opposite configuration of the polyether was observed (absolute configuration of products unknown). Unexpected, however, was the observation that poly-(L)-phenylalanine furnished the opposite enantiomer to that observed employing poly-(L)-leucine. Thus, it has been shown that addition of nucleophiles other than peroxide anion can be catalysed by polyamino acids with significant stereocontrol [22]. 

Acetals and ketals are very important protecting groups in solution-phase synthesis, but only a few constructs have been used as linkers in solid-phase synthesis (Tab. 3.3). The THP-linker (22) (tetrahydropyran) was introduced by Ellman [54] in order to provide a linker allowing the protection of alcohols, phenols and nitrogen functionalities in the presence of pyridinium toluene sulfonate, and the resulting structures are stable towards strong bases and nucleophiles. Other acetal-linkers have also been used for the attachment of alcohols [55, 56]. Formation of diastereomers caused by the chirality of these linkers is certainly a drawback. Other ketal tinkers tike... 

The reactivity of the methoxyethy1idene derivatives with nucleophiles other than water has been examined. It has been already found (13) that they may be readily opened by halogenating reagents ( N -b romo succ i n i-mide for instance) to give a or 3-ha 1 oacetates (respectively from five- or six-membered-ring orthoesters), and this reaction may be compare with the familiar Hanessian procedure for conversion of henzylidene acetals iiito bro-mo-deoXybenzoates (68). ... 

The electrophilic intermediate formed during the Beckmann rearrangement may be trapped by nucleophiles other than water. Strictly speaking, these reactions do not fit into the classical rearrangement reaction type. However, due to the fact that the carbon framework changes during the course of the reaction and to the similarities with the classical Beckmann rearrangement process, this topic will be analysed in the present chapter. 

On the basis of previous results, the Rueping group started to study alkylations with activated alkenes and nucleophiles other than arenes. Recently, Lewis- and Brpnsted-acid-catalyzed hydroalkylation procedures with 1,3-dicarbonyl compounds as nucleophiles have been developed [69, 70]. These reactions primarily utilized Pd... 

The technology was further extended with formation of the ylide by nucleophiles other than the PhaSiH/CsF derived hydride addition (18,19). Cyanide anion, generated from TMSCN/CsF, underwent nucleophilic addition and opening to the... 

When H2O deacetylates the acyl-enzyme, phenylacetic acid is formed. When nucleophiles other than H2O deacylate the acyl-enzyme, a new condensation product, in this case phenylacetyl-O-R or phenylacetyl-NH-R is formed. By definition the hydrolysis of these condensation products can be catalyzed by the same enzyme that catalyzes their formation in equation 10.1. Thus, when the acyl-enzyme is formed from phenylacetyl-glycine or phenylacetyl-O-Me, this gives rise to an alternative process to produce Penicillin G, in addition to the thermodynamically controlled (= equilibrium controlled) condensation of phenylacetic acid and 6-aminopenicillanic acid (6-APA). This reaction that involves an activated side chain is a kinetically controlled (= rate controlled) process where the hydrolase acts as a transferase (Kasche, 1986 1989). 

There is evidence for the formation of Meisenheimer adducts in aqueous solution with nucleophiles other than HzO or OH. The formation of transient adducts has been assumed in the interaction of 160 with the basic components of buffer systems such as carbonate and bicarbonate ions222 and phenoxide ions.224... 

General base catalysis of ester hydrolysis by nucleophiles other than amines and oxyanions has not been characterized, though it would be expected to be closely similar to the reaction involving these bases. Cyanide ion, for example, would be expected to catalyze the hydrolysis of ethyl esters with activated acyl groups, such as ethyl dichloroacetate, by this mechanism. 

In contrast to phosphonic acids, H-phosphinic acids can be coupled with alcohols using carbodiimides to give H-phosphinates 83 (Scheme 31, Table 12).[63-1231 These H-phosphinates 83 afford the corresponding phosphonic acids 84 directly by oxidation with NaI04[123l or by treatment with bis(trimethylsilyl)amide followed by carbon tetrachloride, triethylamine, and waterJ63 Alternatively, as described above (Section 10.10.2.1.3), H-phosphinates may also be converted into the phosphonochloridates by oxidation with carbon tetrachloride and then coupled to nucleophiles other than water, f63-75-76 ... 

The covalent hydration of coordinated heterocycles such as pyridine or phenanthroline has been postulated to account for a variety of anomalous results in hydrolysis reactions. The concept is sufficiently general to encompass attack of nucleophiles other than water (equation 25).98 Reactions of this type have been reviewed very recently and the validity of the covalent hydration concept has come under attack."... 

Nucleophiles other than hydride can be added to support-bound imines to yield amines. These include C,H-acidic compounds, alkynes, electron-rich heterocycles, organometallic compounds, boronic acids, and ketene acetals (Table 10.9). When basic reaction conditions are used, stoichiometric amounts of the imine must be prepared on the support (Entries 1-3, Table 10.9). Alternatively, if the carbon nucleophile is stable under acidic conditions, imines or iminium salts might be generated in situ, as, for instance, in the Mannich reaction. Few examples have been reported of Mannich reactions on insoluble supports, and most of these have been based on alkynes as C-nucleophiles. 

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