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Chapter-5
Synthesis of highly substituted pyrroles
The structures of ADD-01-30 were established on the basis of their elemental
analysis and spectral data (MS, IR, and 1 H NMR). The analytical data for (ADD-05)
revealed a molecular formula C 26 H 24 FNO 3 (m/z 417). The 1 H NMR spectrum revealed
a triplet at δ = 1.06-1.11 ppm assigned to isopropyl-CH 3 , a singlet at δ = 2.22 ppm
assigned to the –CH 3 protons, a quartet at δ = 2.44-2.47 ppm assigned to-CH 2 protons,
two doublets at δ = 4.70-4.73 ppm (j=10.8Hz) and 5.36-5.39 ppm (j=10.8Hz)
assigned to the -CH protons, two multiplets at δ = 7.03-7.35 ppm and triplet at δ =
8.09-8.13 ppm assigned to the aromatic protons, and one broad singlet at δ = 10.16
ppm assigned to -CONH groups.
The structures of AS-01-30 were established on the basis of their elemental
analysis and spectral data (MS, IR, 1 H NMR and 13 C NMR). The analytical data for
(AS-04) revealed a molecular formula C 38 H 42 F 2 N 2 O 5 (m/z 644). The 1 H NMR
spectrum revealed a signals at δ ppm 1.03-1.07 (m, 1H, CH), 1.30-1.63 (m, 18H,
CH 2 , CH & 5 x CH 3 ), 2.24-2.37 (m, 2H, CH 2 ), 2.71 (s, 3H, CH 3 ), 3.66 (m, 1H, CH),
3.86-3.99 (m, 2H, CH 2 ), 4.14-4.17 (m, 1H, CH), 6.83-7.00 (m, 7H, Ar) and 7.12-
7.28 (m, 7H, Ar & NH).
The mechanism for the synthesis of the pyrrole proceeds via Paal-Knorr
reaction, 110 in which protonated carbonyl (B) is attacked by the amine to form the
hemiaminal (C). The amine attacks the other carbonyl to form a 2,5-
dihydroxytetrahydropyrrole (D) derivative which undergoes dehydration in two steps
give the corresponding substituted pyrrole (F).
Figure 28: Proposed mechanism for the formation of pyrroles
Department of Chemistry, Saurashtra University, Rajkot-360005 172