Wagner-Meerwein rearrangement mechanism

A mechanism for formation of the first product by Wagner-Meerwein rearrangement has been proposed. ... 

Reactions. Part. I. The Mechanism of the Wagner-Meerwein Rearrangement. Exchange of Radioactive Chlorine and of Deuterium between Camphene Hydrochloride and Hydrogen Chloride. J. chem. Soc. [London] 1939, 1188. 

The absence of further products, particularly those resulting from -attack on the seleno moiety and those arising from Wagner-Meerwein rearrangements, points to a mechanism involving a non-configurationally selective attack by Cl- or methanol upon the selenira-nium intermediate, as demonstrated below for Cl-. 

Fig. 14.3. Mechanism of an Ar-SE reaction (details Section 5.2.5), which includes a reversible Wagner-Meerwein rearrangement.

Aryl nitrenes show ring expansion to seven-membered ring. The mechanism of ring expansion involves the Wagner-Meerwein rearrangement (Scheme 2.62). 

Higher-chlorinated camphenes are the most plausible side products. They may be formed together with other cyclic carbon skeletons if the Wagner-Meerwein rearrangement (to polychlorinated bornanes) is hindered [38, 39]. The ionic addition of chlorine to the primary olefinic carbon is always in competition with radical chlorination. Although the first mechanism is more likely, the second one may also take place. It was found that a gentle chlorination of... 

The case history of the Wagner-Meerwein rearrangement may serve as a guideline to an extensive discussion of mechanism and stereochemistry of cationic 1,2 shifts. First principles may be derived from the behavior of free carbocations as they occur in the gas phase (Section 2) and in solvents of extremely low nucleophilicity ( superacids ) (Section 3). While such conditions provide valuable information on energetics and some insight into mechanism, they virtually exclude stereochemical studies. 

Thionyl chloride is the classical reagent for the preparation of alkyl chlorides from alcohols with retention of configuration. This reaction is known to proceed via alkyl chlorosulfinates (7 75) which decompose by an ion pair mechanism, but may be diverted to an SN2 displacement path by addition of pyridine171 Wagner-Meerwein rearrangements have been observed in the course of alkylchlorosulfinate decomposition, e.g. (176) - (777)172). The behavior of the isomeric chlorosulfinates (178) and (179) is consistent with competitive ion pair collapse and 1,2-alkyl shift173. ... 

Reaction with unsaturated bicyclic hydrocarbons. From a study of the chlorination of unsaturated bicyclic compounds, Masson and Thuillier1 conclude that the reaction follows, a radical addition mechanism when initiated thermally or photo-chemically. The stereochemistry of the addition is markedly influenced by steric effects. No Wagner-Meerwein rearrangements are observed under these conditions. An ionic mechanism is involved without initiation or in the presence of trifluoroacetic acid in this case the usual carbonium ion rearrangements are observed. 

Rearrangement of the primary halide product (Wagner-Meerwein rearrangement) occurs when HC1 or HBr is added to bicyclic terpenes, especially in solvents of high dielectric constant and when an excess of hydrogen halide is used. For the mechanism see Gould.18d... 

The acid-catalyzed dehydration of an alcohol to a rearranged alkene is known as a Wagner-Meerwein rearrangement. Propose a mechanism for the following Wagner-Meerwein rearrangement ... 

The second type of interaction B, does not lead to the products observed. The simplest mechanism — the usual Wagner-Meerwein rearrangement — accounts neither for the higher rate of solvolysis nor for the predominant migration of cyclopropane. The C-type transition state comprising the delocalization of two cyclopropane bonds accounts for the observed rates and products (cf. however the authors admit that further researdi is necessry for a deeper understanding of the structure of the transition state and of the intermediates. 

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