hydrazine was employed as a coupling partner, substituted pyrazoles 120 were
obtained in good yields.
Further investigations from the same group indicated that highly substituted
pyrroles 123 could be obtained through two sequential copper-catalyzed vinylation
reactions of bis-Boc-hydrazine followed by thermal rearrangement/cyclization
(Scheme 43) [79].
Double alkenylation of amides with (1Z,3Z)-1,4-diiodo-1,3-dienes 124 could
produce di- or trisubstituted N-acylpyrroles 125 with good to excellent yields
(Scheme 44) [80]. The same idea has been applied in the synthesis of dihydropyrroles
and carbazoles [81].
Another efficient method for the synthesis of polysubstituted pyrroles was
described by Li et al. They found that CuI/N,N-dimethylglycine-catalyzed reaction of amines with γ-bromo-substituted γ,δ-unsaturated ketone 126 underwent a
condensation/coupling process to afford pyrroles 127 (Scheme 45) [82].
The intramolecular coupling of 2-iodo substituted tryptophan derivatives 127
could take place in the presence of CuI/DMEDA, affording the corresponding
pyrroloindoles. This tricyclic system has been found in a considerable number of
Scheme 42 CuI-catalyzed synthesis of substituted pyrroles from vinyl halides and Boc-protected
amines
Scheme 43 CuI-catalyzed synthesis of highly substituted pyrroles
Scheme 44 CuI-catalyzed synthesis of substituted N-acylpyrroles
104
Y. Jiang and D. Ma
obtained in good yields.
Further investigations from the same group indicated that highly substituted
pyrroles 123 could be obtained through two sequential copper-catalyzed vinylation
reactions of bis-Boc-hydrazine followed by thermal rearrangement/cyclization
(Scheme 43) [79].
Double alkenylation of amides with (1Z,3Z)-1,4-diiodo-1,3-dienes 124 could
produce di- or trisubstituted N-acylpyrroles 125 with good to excellent yields
(Scheme 44) [80]. The same idea has been applied in the synthesis of dihydropyrroles
and carbazoles [81].
Another efficient method for the synthesis of polysubstituted pyrroles was
described by Li et al. They found that CuI/N,N-dimethylglycine-catalyzed reaction of amines with γ-bromo-substituted γ,δ-unsaturated ketone 126 underwent a
condensation/coupling process to afford pyrroles 127 (Scheme 45) [82].
The intramolecular coupling of 2-iodo substituted tryptophan derivatives 127
could take place in the presence of CuI/DMEDA, affording the corresponding
pyrroloindoles. This tricyclic system has been found in a considerable number of
Scheme 42 CuI-catalyzed synthesis of substituted pyrroles from vinyl halides and Boc-protected
amines
Scheme 43 CuI-catalyzed synthesis of highly substituted pyrroles
Scheme 44 CuI-catalyzed synthesis of substituted N-acylpyrroles
104
Y. Jiang and D. Ma