Rearrangement anionotropic

Treatment of 89 with methanol gives rise to two products 112 and 113 (Scheme 46). The minor compound 113 is formed by protolytic cleavage of 1-boraadamantane, while the major product 112 is obtained as a result of coordination of alcohol to 89 and subsequent 1,2-anionotropic rearrangement <2001JOM(620)51>. 

Organoboration of diacetylenic derivatives proceeds stepwise and in a number of cases is also accompanied by 1,2-anionotropic rearrangement giving rise to polycyclic compounds (see Section 12.13.4.2) <2001CEJ775, 2002CEJ1537>. 

Secondary amines have been prepared from organoboron compounds R1315, R12 BC1 or R1BCI2 (R1 = Et, Bu, /-Bu,, v-Bu, 3-hexyl, cyclopentyl etc.) by treatment with azides R2N3 (R2 = Bu, /-Bu, i-Bu, cyclohexyl, Ph etc.) and aqueous work-up. It is suggested that the reactions proceed by way of anionotropic rearrangements (equation 61)176. 

An example of the anionotropic rearrangement is the reaction of propargyl halides with cuprous salts (Eq. 33). The mechanism and the role of the cuprous salt have not been-completely elucidated. 

Lucchini, Pasquato, and co-workers have obtained stereoisomeric 2,3-disubstituted 1-methylthiiranium ions, reported characterization (1H and 13C NMR, X-ray crystallography), and studied their anionotropic rearrangements. The synthesis was performed by reacting methylbis(methylthio)sulfonium salts with alkenes184,185 (Scheme 4.7). 

Structures of thietanium tetrafluoroborate and hexachloroantimonate salts of 107, formed by anionotropic rearrangement of corresponding thiiranium salts, were obtained by X-ray crystallography and by calculation at the RHF/6-31G //RHF/6-31G level <2001HCA860>. 

Anionotropic rearrangements and displacement reactions yield allenes Allenes are also formed in basic media (Scheme 3.32). The reaction is particularly easy if the migrating hydrogen is adjacent to a second multiply bonded carbon. 

The c/j-3-substituted-2-penten-4-ynal (262) predominantly formed by anionotropic rearrangement of 261 gave, on aldol condensation with methyl ketones, the diyne ketone 263. When a solution of the latter in THF was slowly added to a suspension of finely powdered potassium hydroxide in liquid ammonia, a mixture of the diastereomers of the cyclic glycol 264 was obtained. Treatment of 264 in benzene or ether with tin(ii) chloride dihydrate in concentrated hydrochloric acid gave the... 

Isotopic studies of the anionotropic rearrangements of cis-t-butyi-trans-t-butyl-Dg-thiiranium hexachloroantimonate 25 and its trans-t-butyl-cis-t-butyl-Dg isotopomer 26. 

The intramolecular transfer of the nucleophilic group in Scheme 7 is also claimed to be an SnVo- reaction The anionotropic rearrangement of the di-tert-butylthiirenium ion 7 into the thietium ion 8 involves the stereospecific backside attack of the internal methide at the unsaturated carbon. 

Organoboranes can be used for the synthesis of various organic compounds containing an amino group . The most common procedures involve the reaction of organoboranes with azides, with hydroxylamine derivatives, or with chloroamines. All amination reactions proceed via intermediate formation of a borate complex followed by anionotropic rearrangement to form the new C—N bond (Equation (21)). 

A more convenient procedure for the synthesis of (113) from (5) was later elaborated <9UOM(4l2)l>. It is based on the intramolecular version of the reaction of organoboranes with organic azides. The THF complex of 1-boraadamantane (5a) is treated with iodine in the presence of an excess of sodium azide. The iodine atom in the intermediately formed borabicycle (118) undergoes an easy nucleophilic substitution by azide ions. The subsequent anionotropic rearrangement in the borabicyclic azide (119) leads (after the oxidation of the reaction mixture) to aminoalcohol (120), which is smoothly converted to 1-azaadamantane (113). The yield of (113) in this synthesis is 40-45% based on (5a), or 20-22% based on triallylborane (Scheme 44). 

A number of interesting and useful organic reactions involve isomerizations of substances having one or more carbon-carbon double bonds. This chapter deals with the kinetics of reactions of alkenes, cycloalkenes and substituted alkenes which involve migration of carbon-carbon double bonds, with or without structural alteration of the carbon skeleton of the starting materials. These reactions include prototropic and anionotropic rearrangements, several concerted unimolecular isomerizations such as the Cope and Claisen rearrangements, and a number of non-concerted thermal isomerization reactions. 

Anionotropic rearrangements involve migrations of electronegative groups. They comprise two mechanistically related groups of reactions substitutions and isomerizations. Allylic substitution reactions in which skeletal rearrangement accompanies nucleophilic substitution, viz. 

Qualitative studies of the effects of allylic substituents, acyl substituents, and reaction conditions on rates of isomerization of allylic esters played a prominent role in the development of mechanistic theories of anionotropic rearrangements . Burton and Ingold observed that a-phenylallyl p-nitrobenzoate isomerizes more rapidly than a-phenylallyl acetate, that electron-releasing a-substituents facilitate isomerization of a-substituted allyl acetates, and that the rate of isomerization of a-phenylallyl p-nitrobenzoate increases as the dielectric constant of the solvent increases. All of these observations support the mechanism, which involves dissociation of the allylic ester into an allylic carbonium carboxylate ion pair, which reassociates to the starting material and its allylic isomer, viz. 

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