CHEM01200604012 Dibakar Goswami - Homi Bhabha National ...

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and chemical analysis. 1 H NMR spectra (Fig. II.3.9) of III showed olefinic signals at δ 4.91-5.06 and at δ 5.71-5.91 ppm, whereas the allylic protons gave a doublet at δ 1.69 ppm. Its 13 C NMR spectrum (Fig. II.3.10) showed the peak due to allylic carbon at δ 33.1 ppm. An analogous compound, (CH 2 CH=CH 2 ) 2 GaCl, synthesized following a reported procedure, 88 also provided a similar 1 H NMR spectrum. The sesquibromide, (CH 2 CH=CH 2 ) 3 GaBr 3 , produced 66b in THF, was not formed in [bmim][Br]. The integration of the NMR signals for III reached a maximum (~48%) in ~ 3.5 h, and remained steady even up to 8 h. Addition of 59a to the reaction mixture led to complete depletion of the signal, confirming III as the active organometallic species. Fig. II.3.9. 1 H NMR spectrum of III 61
Fig. II.3.10. 13 C NMR spectrum of III With regard to the activation of Ga metal, a dipole induced dipole interaction with [bmim][Br] was envisaged. The 1 H NMR spectrum of the reaction mixture after incubating [bmim][Br] (5 mL) with Ga (1.0 mmol) for 0.5 h, showed upfield shifts for the imidazole H-2 (3.8 Hz), and H-4 and H-5 (each 3.4 Hz) protons. The shift followed the expected trend, considering maximum positive charge density at C-2 of the imidazole ring. The same trend could also been seen for the imidazole carbons , where an upfield shift of 10 Hz for C-2 and 6 Hz for both C-4 and C-5 were noticed. These results suggested that polarization of Ga metal took place in presence of [bmim][Br] which would activate the Ga-metal surface. The NMR shifts of similar magnitudes are generally attributed to the charge transfer phenomenon. Possibly the combination of Ga and [bmim][Br] initially forms ion pairs or more complex ion-aggregates with an activated Ga (Scheme II.3.7). The 62
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ASYMMETRIC STRATEGIES FOR THE SYNTH
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ACKNOWLEDGEMENTS First of all, I wa
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CONTENTS SYNOPSIS LIST OF FIGURES L
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SYNOPSIS
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models (e. g. Cram’s model, Felki
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4 1d 4-(CH 3 ) 2 CH-C 6 H 4 1 : 1.5
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14. 1n C 6 H 5 CO C 6 H 5 2n 8 77 1
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imetallic systems. In all the cases
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For the benzylation reaction, the c
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O O 3 CHO i O O + OH 13a O O OH O O
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10 3.5 Ga (2.5) THF KI+LiCl 10 55 5
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multidrug-resistant (MDR) cancer ce
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directly afforded the furanose, whi
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References 1. Stephenson, G. R. Adv
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LIST OF FIGURES
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II.3.13 III.1.1 III.1.2 III.1.3 III
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IV.5.2 IV.5.3 IV.5.4 IV.5.5 1 H NMR
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Table Title Page No. II.3.1 II.3.2
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II. .11 PPREAMBLE Demand for specia
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II. .22 IINTRODUCTIION TO CHIIRALII
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The most dramatic example in this a
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H H 2 N OH COOH i PhH 2 CO O H N H
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Methods of Asymmetric Synthesis: 15
Page 51 and 52: O O O O i, ii iii iv HO HO N N OH O
Page 53 and 54: Models for Asymmetric Synthesis. 21
Page 55 and 56: If a strongly electronegative group
Page 57 and 58: enantiomeric products are formed at
Page 59 and 60: vi) The balance between chiral auxi
Page 61 and 62: IIII. .11 IINTRODUCTIION TO CHIIRAL
Page 63 and 64: Scheme II.1.2 However, availability
Page 65 and 66: Prof. R. Noyori received the Nobel
Page 67 and 68: Apart from the cinchona alkaloids,
Page 69 and 70: ligand, it assumes a tetrahedral co
Page 71 and 72: Marshall. 53 More recently, Barbero
Page 73 and 74: Various protocols have been develop
Page 75 and 76: In the absence of a sterically-bulk
Page 77 and 78: IIII. .33. . PPRESSENT WORK It is w
Page 79 and 80: [pyridinium][Sn 2 Cl 5 ] etc. can b
Page 81 and 82: RCHO 59a-j i R OH 60a-j (i) Allyl b
Page 83 and 84: Fig. II.3.2. 1 H NMR spectrum of 60
Page 85 and 86: in [bmim][BF 4 ] using sub-stoichio
Page 87 and 88: The reaction in THF was also follow
Page 89 and 90: The integration of the signal at δ
Page 91 and 92: The standard reduction potential of
Page 93 and 94: It has also been reported, 83a,b th
Page 95 and 96: IIII. .33. .33 Gaal lliuum meeddi i
Page 97 and 98: 5 3.0 5.0 THF LiCl+KI c 14 d 71 6 1
Page 99 and 100: 3 59d 4-(CH 3 ) 2 CH-C 6 H 4 H 60d
Page 101: Fig. II.3.8. 13 C NMR spectrum of 6
Page 105 and 106: fragmentation peak at m/z 138 (19%)
Page 107 and 108: Fig. II.3.13. 13 C NMR spectrum of
Page 109 and 110: active catalyst, as suggested for t
Page 111 and 112: 1-(4-Bromophenyl)-but-3-en-1-ol 59b
Page 113 and 114: 1H), 7.90-7.93 (m, 1H); 13 C NMR:
Page 115 and 116: 662, 980, 1079, 1332, 1374 cm -1 .
Page 117 and 118: IIIIII. .11 DIIASSTEREOSSELECTIIVE
Page 119 and 120: cyclohexylideneglyceraldehyde (1) 3
Page 121 and 122: mixture of Zn dust, allyl or γ-sub
Page 123 and 124: Fig. III.1.2. 13 C NMR spectrum of
Page 125 and 126: Reaction with crotyl bromide: In ca
Page 127 and 128: Fig. III.1.5. 1 H NMR spectrum of 6
Page 129 and 130: The formation of the 2,3-anti addit
Page 131 and 132: To establish the C-4 configuration
Page 133 and 134: Allylation with (E) and (Z)-1-bromo
Page 135 and 136: (i) Zn, aqueous satd. NH 4 Cl, THF,
Page 137 and 138: Fig. III.1.12. 1 H NMR spectrum of
Page 139 and 140: Allylation with 1-Bromo-4-(tert)-bu
Page 141 and 142: fast and gave a significantly bette
Page 143 and 144: espectively) due to the cyclohexyli
Page 147 and 148: was treated with excess amount of b
Page 149 and 150: Fig. III.1.20. 1 H NMR spectrum of
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stereochemistry of allylation of β
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of the products were modest (48-62%
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6 1.2 In (2.0) H 2 O LiCl+ KI 14 72
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are consistent with our previous re
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III.3 EXPERIMENTAL SECTION: General
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(2R,3R)-1,2-Cyclohexylidenedioxy-5-
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for an additional 2 h, gradually br
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(m, 2H), 5.82-5.98 (m, 1H), 7.25-7.
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31.6, 32.2, 63.4, 128.8, 133.0. Ana
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23 (2R,3S,4R)-1,2-Cyclohexylidenedi
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(2R,3S,4S)-1,2-Cyclohexylidenedioxy
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(m, 1H), 3.50-4.02 (m, 5H), 4.10-4.
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and dried. Removal of solvent in va
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ine, and dried. Solvent removal und
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IIV. .11 SSYNTHESSIISS OFF ENANTIIO
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Scheme IV.1.1 The same group also d
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IV.1.3: Present work Although sever
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O O C 6 H 13 i O C 6 H 13 ii OH C 6
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Fig. IV.1.4. 1 H NMR spectrum of 10
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the unit-C contribute positively to
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tartrate, Ti(O-i-Pr) 4 , CH 2 Cl 2
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Based on this hypothesis, the alcoh
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OR 3 O R 1 R 2 NaBH 4 H H R 1 R 1 +
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(OH). Oxidative cleavage of its α-
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IIV. .33: : SSYNTHESSIISS OFF 33' '
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For the actual synthesis, (Scheme I
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IV.4: SSYNTHESSIISS OFF 22( (SS) )-
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(i) PhCHO, triethyl orthoformate, M
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O N 3 II Ph HO OH b1 N 3 Ph O O Ben
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Thus, easily accessible 1 has been
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167 and subsequent reduction gave 1
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from the appearance of 13 C NMR pea
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IV.6 EXPERIMENTAL SECTION (2R,3S,4R
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As described earlier, compound 108
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19.5, 23.8, 23.9, 25.1, 26.9, 34.6,
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74.2, 74.4, 110.1, 116.7, 127.6, 12
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mmol) in MeOH (10 mL), work up, fol
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7.51 (m, 3H), 7.92-8.08 (m, 2H); 13
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subsequent isolation afforded rotam
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4.18 (t, J = 3.4 Hz, 1H), 4.75-4.84
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-4.21 (c 1.2, CHCl 3 ); IR: 3466, 1
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(3R)- 3,4-O-Cyclohexylidene-2-oxo-1
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Water and EtOAc was added to the mi
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24 179. Yield: 1.49 g (77.5%); colo
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24 furnished pure 183. Yield: 0.37
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1. Wender, P. A. Chem. Rev. 1996, 9
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17. Hanessian, S.; Maji, D. K.; Gov
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32. For some selective references s
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43. (a) Cleare, M. J.; Hydes, P. C.
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54. Barbero, A.; Pulido, F. J.; Rin
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2008, 1681. (d) Fargeas, V.; Zammat
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72. Karodia, N.; Guise, S.; Newland
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Kaminski, J.; Millhauser, G.; Ortiz
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Böhm, V. P. W.; Reisinger, C. J. O
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119. Wender, P. A.; Holt, D. A.; Si
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140. (a) Chemler, S. R.; Roush, W.
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Lett. 1996, 107, 53. (c) Smith, C.
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158. Mitsuya, H.; Weinhold, K. J.;
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L.; Zugay, J. A. J. Med. Chem. 1993
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1. Goswami, D.; Chattopadhyay, A.;
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