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To avoid lithiation, Ohta has shown that 2-bromoimidazoles can undergo palladium catalyzed coupling with trimethylsilylazide (Scheme-1.10.12). Reduction again provides the 2-aminoimidazole. This strategy has been implemented by Ohta’s group to access several Leucetta alkaloids discussed below. Also, noteworthy, Ohta has shown that during reduction of the azide it can be directly protected as its benzylidenimine. 101-102 N N Br TMSN 3 PdCl 2(PPH 3) 2 80 o C N N N 3 H2, Pd-C Scheme-1.10.12 Ohta’s palladium catalyzed synthesis. 1.10.4 Heterocyclic Exchange Reactions The transformation of 3-amino-1,2,4-oxadiazoles to 2-aminoimidazoles can be carried out by reaction with fluorinated ß-dicarbonyls to give the ß-hemiaminal (Scheme- 1.10.13). 103 This can undergo subsequent conversion to the 2-amidoimidazole through a Boulton-Katritzky Rearrangement. This intermediate can then be reduced to give Intermediate. The benzamide can also be removed via acid catalyzed hydrolysis to give the trifluoromethyl amino-imidazole. An interesting reaction, however the synthesis of the intermediate ß-enaminocarbonyl is low yielding and initial results suggest limited substituent scope, as the initial condensation requires the presence of the trifluoromethyl ketone. Ph O O N NH 2 N O CF 3 R Montmorillonite K-10, PhMe, 100 o C; Ph F3C HN OH O N N O R Ph O N H Ph N F3C HN OH OH N N O R NaBH 4 THF reflux Scheme-1.10.13 Boulton-Katritzky rearrangment of aminooxadiazoles. N H CF 3 OH R N N Ph NH 2 O N H N N H N 2N H N H CF 3 HCl EtOH reflux CF 3 O R O R
Another route to 4(5)-acyl-2-amino-1H-imidazoles is based on the recyclization of 5acyl-2-amino-1,3-oxazoles (Scheme-1.10.14). 104 For example, 5-acetyl-2-aminooxazole gave upon heating in water solution with ammonia or aliphatic amines 2amino-1H-imidazoles in 32% (R = H) and 43-62% (R = alkyl or cycloalkyl) yields. Me O N O NH 2 NH 3 or Amine H 2O, heating Me O N N H NHR Scheme-1.10.14 Mularski’s recyclization method. Methodology to prepare 2-aminoimidzoles has greatly advanced due to the rising demand in natural product synthesis and medicinal chemistry. However, the development of methods to succinctly generate a highly functionalized 2aminoimidazole core from stable precursors is warranted. 1.11 The 2-Aminoimidazole as a Pharmacophore The 2-aminoimidazole has been utilized as a building block has led to the development of several medicinally relevant small molecules. 1.11.1 Antibiotics Activity Researchers at Zeneca delivered a series of broad spectrum antibiotics a-c, inspired by the well studied cephalosporins. 106-106 They were further able to show that substitution on N1 of the aminoimidazole led to inactive compounds, again suggesting that this motif may make an acid hydrogen bond contact (Fig. 1.11.1). Interestingly they were able to correlate the pKa of the 2-aminoimidazole with activity. Against Gram positive organisms they found that a slight elevation in the pKa led to a dramatic decrease in activity. For Gram-negative bacteria, there was little difference, suggesting pKa may alter the membrane permeability.
Page 1 and 2: Saurashtra University Re - Accredit
Page 3: JANUARY-2011 Statement under O. Ph.
Page 7 and 8: Acknowledgment This thesis arose in
Page 9 and 10: since I was a child. My Mother Hans
Page 11 and 12: CHAPTER - 2 Microwave Assisted Synt
Page 13 and 14: 5.5 Results and discussion 156 5.6
Page 15 and 16: Ms Mesyl MW Microwave NBS N-bromosu
Page 17 and 18: 1. Microwave Assisted Organic Synth
Page 19 and 20: 1.4 Heating Mechanism In microwave
Page 21 and 22: 1.5. Effects of solvents Every solv
Page 23 and 24: 1.7 Application of microwave in org
Page 25 and 26: aromatic amines, Lancini’s group
Page 27 and 28: 1.9 2-Aminoimidazole Alkaloids The
Page 29 and 30: Recently group of Erik 83 described
Page 31 and 32: 1.10 Methods for the preparation of
Page 33 and 34: R 1 O X R 2 NH 2 H 2N NAc R 1 HN R
Page 35: this manifold, was reported in 1925
Page 39 and 40: this series of compounds against th
Page 41 and 42: documented. Extra care is needed be
Page 43 and 44: Very recently the research group of
Page 45 and 46: OH a,b O N H2N N Boc N 3 H N R N N
Page 47 and 48: 1.12.2 Biofilm Growth Cycle 1) Plan
Page 49 and 50: can survive both the onslaught of a
Page 51 and 52: [26] Leadbeater, N. E. (2004) Chemi
Page 53 and 54: [86] Kreutzberger, A. (1962) J. Org
Page 55 and 56: Microwave Assisted Synthesis & Stru
Page 57 and 58: 2.1 Introduction As described in ch
Page 59 and 60: 2.3 Proposed Mechanism: Regarding t
Page 61 and 62: No. 12 60 120 traces 84 a All react
Page 63 and 64: the development of biofilm related
Page 65 and 66: In first instance, a series of 2-hy
Page 67 and 68: Br N N N R 1 OH Br N N N R 1 OH Fig
Page 69 and 70: do have a very strong effect agains
Page 71 and 72: 2.6 Conclusion In the present study
Page 73 and 74: 2.8 Biological assays 2.8.1 Static
Page 75 and 76: 2.9 Experimental protocol: 2.9.1 Ge
Page 77 and 78: temperature of 80 °C and a maximum
Page 79 and 80: 29.5,29.4, 29.2, 27.0, 22.6, 14.1.
Page 81 and 82: Yield: 78 %. 1 H NMR (300 MHz, CDCl
Page 83 and 84: N Br N N C 14H 29 OH Yield: 72 %. 1
Page 85 and 86: (75.5 MHz, CDCl3): δ = 167.7, 154.
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N Br N N C 14H 29 OH Cl Yield: 90 %
Page 89 and 90:
2-(3,4-Dichlorophenyl)-2-hydroxy-1-
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N Br N N C 8H 17 OH NO 2 Yield: 49
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C3H7 HN N N H Cl Cl Yield : 70 %. 1
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(s, 1H), 3.16 (s, 3H), 1.80 (m, 2H)
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5-(4’-Nitrobiphenyl-4-yl)-N-octyl
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2.11 Representative NMR spectra 2.1
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2.11.3 10.4329 0.7429 151.5720 10.0
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[21] Matz C, McDougald D, Moreno A.
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Chapter-3 Structure Activity Relati
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imidazoles, where the addition of a
Page 109 and 110:
3.4 Result and Discussion It was fo
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No. H 2N Compound Code N N C8H17 R1
Page 113 and 114:
medium used in the set-up to monito
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H 2N N N N H2N N R R Figure-1 Effec
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3.5.3 Cyclo-alkyl 2-aminoimidazoles
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3.6. Conclusion In the present stud
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3.8. Experimental protocols 3.8.1 G
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122.6, 54.6, 33.3(×2), 27.3 (×2),
Page 125 and 126:
Yield: 52 %. 1 H NMR (300 MHz, CDCl
Page 127 and 128:
5-(4-Chlorophenyl)-1-cyclooctyl-1H-
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Yield: 50 %. Mp: 76-78 ° C. 1 H NM
Page 131 and 132:
5-(4-Chlorophenyl)-1-cyclobutyl-1H-
Page 133 and 134:
Yield: 66%. 1 H NMR (300 MHz, CDCl3
Page 135 and 136:
3.10 Representative NMR spectra 3.1
Page 137 and 138:
3.11 References [1] (a) Alvi K. A,
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Copper Catalyzed Microwave Assisted
Page 141 and 142:
4.1 Introduction There are only a f
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(Table-1, No- 6). Next reaction tem
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No. Product, Yield b (%) No. Produc
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4.4 Possible Mechanism Regarding th
Page 149 and 150:
4.7 Experimental protocols 4.7.1 Ge
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Yield: 69 %. 1 H NMR (300 MHz, CDCl
Page 153 and 154:
1-(3-Azidopropyl)-2-(3,4-dichloroph
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Yield: 84 %. 1 H NMR (300 MHz, DMSO
Page 157 and 158:
Page 159 and 160:
Page 161 and 162:
1H), 1.66 (m, 6H), 1.70 (m, 2H). 13
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5.48 Hz, 2H), 3.59 (m, 2H), 3.16 (d
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4.10 References [1] For a general r
Page 167 and 168:
Crystal and Molecular Structure Ana
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5.1 Introduction The membrane efflu
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oscillation range of 5˚ and proces
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C12-C13 1.372(4) C32-C37 1.390(3) C
Page 175 and 176:
Fig.-3: Packing of the molecules wh
Page 177 and 178:
1 H NMR (400 MHz CDCl3): δ = 7.57-
Page 179 and 180:
5.9.2 13 C spectra of bs-DP-7
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SUMMARY The work represented in the
Page 183 and 184:
CONFERENCES/SEMINARS/WORKSHOPS ATTE
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PUBLICATIONS [1] One-Pot Microwave-
Page 200 and 201:
Scheme 2 Competitive formation of 1
Page 202 and 203:
Table 2 continued 9 10 11 12 N hydr
Page 204:
8. Colson G, Raboult L, Lavelle F,
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