Abstract
Deprotonation of 2-alkenylbenzaldehyde N -benzylimines by lithium diisopropylamide and subsequent addition of pivaloyl chloride or methyl chloroformate yields 2-acylated 2,3-dihydro-1H -benzo[c ]azepines. This reaction is interpreted as a cascade involving a 1,7-electrocyclization reaction and a subsequent 1,5-hydrogen shift. In contrast, 2-prop-1-enylbenzaldehyde N -allylimine leads to an N-acylated (5,6-dihydrobenzocycloocten-5-yl)amine upon deprotonation and addition of pivaloyl chloride. This transformation is interpreted as a reaction sequence consisting of a 1,7-electrocyclization, the addition of the electrophile, another deprotonation and a [2,3]-aza-Wittig rearrangement, which proceeds in two steps according to quantum chemical calculations.
Key words
ring closure - lithium - rearrangements - heterocycles - carbocycles - quantum chemical calculations