Electrophilic addition reactions hydrolysis

Diels-Alder reaction, 493 El reaction, 391-392 ElcB reaction, 393 E2 reaction, 386 Edman degradation, 1032 electrophilic addition reaction, 147-148. 188-189 electrophilic aromatic substitution, 548-549 enamine formation, 713 enol formation, 843-844 ester hydrolysis, 809-811 ester reduction, 812 FAD reactions. 1134-1135 fat catabolism, 1133-1136 fat hydrolysis, 1130-1132 Fischer esterification reaction, 796 Friedel-Crafts acylation reaction, 557-558... 

Additions of acetals and orthoesters to enol ethers probably represent the most intensively studied class of Lewis acid promoted reactions in the chemistry of aliphatic compounds. Since usually catalytic amounts of BFg OEta have been employed, concentration control (rule A) should predominate. Unlike the solvolyses of alkyl halides, the acid catalyzed hydrolyses of acetals and orthoesters do not follow a rate equilibrium relationship so that the corresponding hydrolysis rates cannot be used for the analysis of electrophilic addition reactions. We have, therefore, carried out competition experiments to determine relative reactivities of acetals and orthoesters towards methyl vinyl ether in presence of catalytic amounts of BF3 0Et2 (Figure 11). As the reactivity order towards other ir nucleophiles can be expected to be similar, the krei values of Figure 11 can be used to rationalize or predict the results of acetal and orthoester additions 1 1 Adducts can only be generated selectively if the k ei values of the designed products are smaller than the k Qi values of the reactants. 

The highly electrophilic character of the POf ion would suggest a very unselective phosphorylation behavior. For example, the ratio of alkyl phosphate to inorganic phosphate obtained in hydrolyses of phosphoric esters in water/alcohol mixtures should reflect the molar ratio of water and alcohol. This is indeed found in numerous cases, e.g. in the hydrolysis of phenyl and 4-nitrophenyl phosphate monoanions 97) or of 4-nitrophenyl phosphate dianions 65) at 100 °C in methanol/ water mixtures of various compositions, as also in the solvolysis of the acetyl phosphate dianion at 37 °C 97) or of phosphoenol pyruvate monoanions 82). Calculations of the free energy of the addition reactions of water and ethanol to the POf ion support the energetic similarity of the two reactions 98) (Table 4). 

Marchand and co-workers reported a synthetic route to TNAZ (18) involving a novel electrophilic addition of NO+ NO2 across the highly strained C(3)-N bond of 3-(bromomethyl)-l-azabicyclo[1.1.0]butane (21), the latter prepared as a nonisolatable intermediate from the reaction of the bromide salt of tris(bromomethyl)methylamine (20) with aqueous sodium hydroxide under reduced pressure. The product of this reaction, A-nitroso-3-bromomethyl-3-nitroazetidine (22), is formed in 10% yield but is also accompanied by A-nitroso-3-bromomethyl-3-hydroxyazetidine as a by-product. Isolation of (22) from this mixture, followed by treatment with a solution of nitric acid in trifluoroacetic anhydride, leads to nitrolysis of the ferf-butyl group and yields (23). Treatment of (23) with sodium bicarbonate and sodium iodide in DMSO leads to hydrolysis of the bromomethyl group and the formation of (24). The synthesis of TNAZ (18) is completed by deformylation of (24), followed by oxidative nitration, both processes achieved in one pot with an alkaline solution of sodium nitrite, potassium ferricyanide and sodium persulfate. This route to TNAZ gives a low overall yield and is not suitable for large scale manufacture. 

In addition to the protected pyrroles mentioned above, the 1-azafulvene dimer formed by Mannich reaction of pyrrole-2-carboxaldehyde with di-methylamine has also been successfully lithiated adjacent to both pyrrole nitrogens (Scheme 10). Reaction with electrophiles and subsequent hydrolysis leads to 5-substituted pyrrole-2-carboxaldehydes in good yield [88TL777 92JOM(423)173]. 

A range of methods has been developed for the protection of the carbonyl group in multifunctional aliphatic and alicyclic aldehydes and ketones. This has been necessary because in many multistage syntheses, modification of other functionalities (e.g. oxidation, reduction, hydrolysis, nucleophilic and electrophilic additions and displacements, etc.) requires a differing range of experimental conditions, and that protective group must be selected which is stable in the presence of the reaction medium. A further feature that should be noted is that... 

Treatment of a,a-dicyanoalkyl phenyl selenide (14) with vinyl ether initiated by AIBN under benzene refluxing conditions generates methyl ketone (15) (eq. 4.8). An electrophilic a,a-dicyanoalkyl radical is first formed, and then it adds to vinyl ether, followed by hydrolysis. Diethyl 3-iodoalkylphosphonate (17) can be formed through AIBN-initiated addition reaction of diethyl 1-iodomethylphosphonate (16) to alkene (eq. 4.9). This is an atom-transfer reaction. Both reactions (eqs. 4.8 and 4.9) do not require Bu3SnH. 

The Sn-0 bond in the alkylperoxytin compounds will in all probability show the same substitution and addition reactions as it does in alkoxytin compounds, but few studies of these reactions have been reported. In the air, hydrolysis occurs, and the stannyl peroxides, ROOSnBu3, have been shown to react with electrophiles such as triphenylmethyl chloride, methoxymethyl chloride, t-butyldimethylsilyl triflate, and acyl halides or acid anhydrides to give the peroxides R00CPh3, ROOCH OMe, ROOSiMeaBu1, and ROOCOR, respectively. 137-146... 

The electrophilic addition of a Lewis acid to a lone pair to form a Lewis salt is an isoelectronic reaction. An example is the first step of borate ester hydrolysis ... 

Reductive opening of 2-phenyltetrahydrothiophene (30) takes place by treatment with lithium in the presence of a catalytic amount of DTBB at low temperature to give the benzylic dianion (31) in a similar way as for thietane (22) (e.g., see Section II.B). The reaction with electrophiles followed by hydrolysis gives functionalized thiols (32). The treatment of the sulfanyl alcohol obtained by addition of acetone as electrophile with 85% phosphoric acid leads to the expected tetrahydrothiopyran (33) (Scheme 10) (97T5563). 

---