Transannular hydride shift

A number of the purported syntheses of dibenzo[f>,/][l,4]diazocines in the literature have to be revised and the structure of the products corrected.1 Instead of the expected 1,4-diazocine derivatives 1, isoindolobenzimidazoles 2 are actually isolated, the formation of which requires a hydride shift after transannular attack of one imine group onto the other. 

The above is a typical example of a transannular hydride shift. The 1,2-diol is formed by a normal epoxide hydrolysis reaction (10-7). For a discussion of 1,3 and... 

In some transannular hydride shifts, hydride participation in the ratedetermining step does, however, seem to occur.132... 

Transannular hydride shifts, first detected by Cope and coworkers in solvolyses of cyclooctene oxide, have subsequently been found in a number of related systems, e.g. cyclooctadiene monoepoxides, CA o-bicyclo[3.3.1 ]non-2-ene epoxide and l-oxaspiro[2.6]nonane. In general these reactions do not involve skeletal rearrangements, and they will not be discussed in detail. 

Transannular 1,5-hydride shifts are often seen across medium-sized (8-, 9-, and 10-membered) rings. The atoms directly across from each other in these rings are quite close together, so migration is facile. In general, though, most cationic rearrangements can be accounted for by a series of 1,2-shifts. 

Chlorination of cis-cyclooctene with SbCls involves a transannular 1,5-hydride shift a mixture of cis- and trans-l,4-dichlorocyclooctane is obtained in 78% yield. 

Transannular 1,5-hydride shifts are often seen across medium-sized (8-, 9-, and... 

Transanuular 1,4-hydride shift. When (1) is healed with KOH in /-butanol-water (35 1), it rearranges to (2). Evidence was obtained that a transannular... 

As further evidence of the reluctance of alkyl groups to undergo transannular shifts, cyclodecane-1,6-diol does not form any ketone on acid treatment. More distant hydride shifts can also be studied, such as 1,4 and 1,5 hydride shifts. 

Products available from the transannular reactions described so far have been exploited as substrates for further transformations, some involving 1,5-hydride shifts in reverse . 

Stehelin, L., J. Lhomme, and G. Ourisson Transannular Hydride Shifts. A Mechanistic Study in the Longifolene Series. J. Amer. Chem. Soc. 93, 1650 (1971). 

Relatively less is found at C(4). This result can be explained by a transannular hydride shift ... 

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