Site selective hydrogen/metal exchange: competition and cooperation between superbases and neighboring groups

A review with 62 refs. The appropriate choice of a metalating reagent is the key to the optional deprotonation of benzylamine derivs. at a position adjacent to the substituent or the nitrogen bearing side chain or even at the benzylic a-position of the latter. Subsequent reaction with suitable electrophiles followed by cyclization affords heterocyclic products such as isoquinolines and isoindolones. Immediately when generated, some organometallic intermediates can undergo a rapid second hydrogen/metal exchange process. However, demetalation is only kinetically, not thermodn. favored as a careful investigation of typical cases has revealed. Moreover, it can be avoided if the donor capacity of the solvent or the polarity of the metalating reagent is increased. Allylic organopotassium compds. exhibit intriguing stereopreferences. This peculiarity has been exploited in a no. of very simple sesquiterpene syntheses. [on SciFinder (R)]