Indoline ring enamines

Members of the tetracyclic dibenzopyrrocoline alkaloid family can be prepared by the intramolecular ring closure of l-(o-halobcnzyl)-tetrahydroisoquinoline derivatives. (3.38.)47 The analogous transformation of dihydroisoquinolines (3.39.) proceeds probably through the isomeric enamine form obtained by the tautomeric shift of the double bond 48 The palladium-carbene catalyst system applied in these reactions was also effective in the preparation of indoline, indolizidine and pyrrolizidine derivatives 49... 

Interestingly, the enamine of cyclopentanone 144, upon irradiation [72], gave only the cis-indoline 145 in 52% yield this indicated the effect of ring-strain on the stereochemistry of the indolines (Scheme 8.42). Mechanistically, several pathways... 

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