The functionalization of aromatic molecules and heterocyclic
compounds has often been achieved by metalation using
various bases.11 However, the deprotonation of functionalized
nonaromatic and olefinic systems is more difficult and sensitive
compared with that of aromatic and heteroaromatic systems.12
Excellent work by Knochel’s group described the magnesiation
or zincation of highly functionalized alkenes and cycloalkenes
using 2,2,6,6-tetramethylpiperidyl base (Scheme 2).12a During
the course of our continued work on the preparation of
heterocycles from enaminones,13 we developed an efficient
cascade addition/cyclization reaction to synthesize 3-amino-
2,5-aryl (or alkyl) furans promoted by LDA, from enaminones
and aldehydes, inspired by the β-metalation of unsaturated
olefins facilitated by the orientation effect on the carbony