Isoindolinium salts

In contrast to isoindolinium salts and A-oxides of isoindolines, successful elimination from simple 2-substituted isoindolines has been realized in only two cases. One of these, however, was the synthesis of isoindole itself, and it seems likely that this method is particularly well suited to the preparation of other sensitive isoindoles. 

TL2877>. The reaction is very sensitive to the length of the allyl side chain. As it is increased there is greater competition from an alternative cyclisation in which isoindolinium salts are formed. 

Dimethyl-2,3-dihydro-l( 0 lienz[c]azepinium salts may be obtained by the palladium-catalyzed cyclization of 3-acetoxy-3-(2-dimethylaminomethylphenyl)-prop-l-enes <94TL2877>. However, if the alkene chain is extended there is an increasing tendency towards the formation of dihydro-isoindolinium salts (Scheme 21). 

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