Rearrangement, 1,2-alkyl oxygen

The intermediate enol silyl ether permits further regioselective substitutions such as bromination followed by dehydrobromination (Eq. 81)49> and alkylation (Eqs. 82 93) and 83 103)). Thus, in addition to activating the rearrangement, the oxygen substituent regioselectivity creates an enol silyl ether, a powerful enolate synthon. 

No rearranged products were formed during the formation and hydrolysis of neopentyl acetate 4 or a-methylallyl acetate.5 If free carbonium ions had been obtained by an alkyl-oxygen fission, we should expect rearrangement products (see pp. 44, 57). 

The solvolysis of the glucosides (164) leads to products that apparently result from both R2O-3 participation by ring oxygen and 0-4 participation by the acetoxy alkyl oxygen. The concerted nature of the proposed second step [Eq. (40)] is doubtful owing to the strain involved. A prior rearrangement, as previously suggested, may occur [e.g., see (97) and (155)]. 

Sulfuric acid reacts with primary and secondary alcohols by a bimo-lecular displacement reaction with no alkyl-oxygen fission. The mechanism of the reaction is similar to the acid-catalyzed esterification of carboxylic acids. Sulfation of optically active 2-butanol gives a sulfate ester with complete retention of configuration. In addition, neopentyl alcohol sulfates without rearrangement. 

The reduction of alkyl-substituted siUcon and tin peroxides with sodium sulfite and triphenylphosphine has been reported (33,93). Alkyl-substituted aluminum, boron, cadmium, germanium, siUcon, and tin peroxides undergo oxygen-to-metal rearrangements (33,43,94), eg, equations 22 and 23. 

Methoxydimethylsulfonium and Trimethylsulfoxonium Salts. Alkylating agents react with DMSO at the oxygen. For example, methyl iodide gives methoxydimethylsulfonium iodide (10) as the initial product. The alkoxysulfonium salts are quite reactive and, upon continued heating, either decompose to give carbonyl compounds or rearrange to the more stable trimethylsulfoxonium salts, eg, (11) (eq. 21) (52) ... 

An alkyl group can also migrate from oxygen to nitrogen or phosphorus [I, 72] (Michaelis-Arbuzov rearrangement) With this methodology, tetrafluoro-pyndine phosphonates and phosphmates can be obtained [75, 74], Chlorine fluoride... 

The rupture of the oxazirane ring at the ON-bond occurring with acid treatment of the alkyl-substituted compounds is probably the result of an electronic shift initiated by the protonated oxygen (arrows as in 21). In principle, a similar rearrangement of the electronic system should also be possible initiated from the nitrogen end (22), Indeed, decomposition products similar to those of the... 

The carbocations generated by non-Kolbe electrolysis can rearrange by alkyl, phenyl or oxygen migration. The migratory aptitudes of different alkyl groups have been studied in the rearrangement of a-hydroxy carboxylic acids (Eq. 34) [323]. 

A 1,2-shift has been observed in radicals bearing an OCOR group at the p-carbon where the oxygen group migrates as shown in the interconversion of 36 and 37. This has been proven by isotopic labeling experiments and other mechanistic explorations. A similar rearrangement was observed with phosphatoxy alkyl radicals such as 38. ... 

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