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Chapter 4 Synthesis of highly substituted pyrazolopyrimidine one broad singlet at δ = 5.57 ppm assigned to –NH 2 groups, one singlet at δ = 7.28 ppm assigned to –CONH groups and one broad singlet observed at δ = 11.9 ppm assigned to pyrazole -NH. The structures of 9a-x were established on the basis of their elemental analysis and spectral data (MS, IR, and 1 H NMR). The analytical data for 9i revealed a molecular formula C 16 H 21 NO 2 S 2 (m/z 323). The 1 H NMR spectrum revealed a singlet at δ = 1.18-1.20 ppm assigned to isopropyl-CH 3 , a singlet at δ = 1.57 ppm assigned to the –CH 3 protons, a singlet at δ = 2.44 ppm assigned to (2 × SCH 3 ) , a multiplet at δ = 3.17-3.24 ppm assigned to the isopropyl -CH protons, a multiplets at δ = 6.99–7.54 ppm assigned to the aromatic protons, and one broad singlet at δ = 8.38 ppm assigned to -CONH groups. The structures of 10a-x 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 10b revealed a molecular formula C 23 H 26 ClN 5 O 2 S 2 (m/z 503). The 1 H NMR spectrum revealed a multiplets at δ = 1.35-1.81 assigned to 10 protons of (5x CH 2 ) groups in cyclohexane ring, a singlet at δ = 2.45 ppm assigned to - SCH 3, a singlet at δ = 2.70 ppm assigned to - CH 3, a multiplet at δ = 3.79 ppm assigned to the –CH protons of cyclohexane ring, a multiplet at δ = 7.05–8.00 ppm assigned to the aromatic protons, one singlet at δ = 8.56 ppm assigned to –CONH groups attached with cyclohexane ring, and one singlet observed at δ = 12.56 ppm assigned to –CONH group attached with phenyl ring. The proposed mechanism for the cyclization is shown in Figure-24. The endocyclic-NH in compound A is the most nucleophilic center it is also the most sterically hindered site. Therefore, addition takes place at the exocyclic-NH 2 groups. The nucleophilic amino group attacks on the double bond via a Michael addition reaction, followed by loss of the thiomethane group. The intermediate D then cyclizes with subsequent dehydration E to afford the pyrazolopyrimidine derivative F. Department of Chemistry, <strong>Saurashtra</strong> university, Rajkot-360005 136
Chapter 4 Synthesis of highly substituted pyrazolopyrimidine Mechanism:- S HN O S HN O R O R 1 HN N NH 2 N NH NH 2 S S SCH 3 HN S O N N N R 1 S R F -H 2 O S A HN N N HO R 1 R E O H N S B HN S N NH O R 1 D O H N S R -SHCH 3 N H O S H H S N NH N C O R R 1 Figure 24: Proposed mechanism for the formation of pyrazolopyrimidine. Department of Chemistry, <strong>Saurashtra</strong> university, Rajkot-360005 137
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Saurashtra University Re - Accredit
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Statement under O.Ph.D.7 of Saurash
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I am thankful to FIST/DST and SAP/U
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Chapter 4 Synthesis and Characteriz
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Chapter - 1 Palladium Catalyzed Syn
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Chapter 1 Synthesis of functionaliz
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Chapter - 2 Synthesis and Biologica
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Chapter 3 Synthesis of trisubstitut
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pyrazole derivative were faster and
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Conferences participated 1. “15 t
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