My PhD dissertation - Institut Fresnel

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6 The second part of this work sets out to assess the relative stabilities of several primary, secondary and tertiary alkyl anions by means of a well known reaction. Hence, by preparing mixed tetraalkyl phosphonium halides, each one bearing two different type of alkyl group, and submitting them to alkaline decomposition, one whish to determine kinetic parameters related to their relative stabilities as probable carbanions. Furthermore, since expulsion of alkyl groups is assumed to be governed by their relative stability and is proposed to be stemming from the decomposition of a common transition state in the rate determining step, the kinetic data provided by this study should legitimately be compared with computed or gas-phase thermodynamics. R 1 R 2 P + R O 1 R2 OH ∆G1 R 1 P R 2 R 1 R 2 X OH R 1 R 2 P R O 1 Several research groups previously evaluated the ease of anion expulsion by analyzing the decomposition products of some tetraaryl or aryl-alkyl mixed phosphonium salts. Nevertheless, due to the practical difficulty to prepare and handle the majority of trialkyl phosphorus compounds, very few tetraalkyl phosphonium salts were studied by this decomposition reaction ∆G 2 + R 2 [30, ] 52 . Furthermore, the ratios of phosphine oxides and anions expulsed were generally measured either by direct isolation of the oxides or by gas chromatography analysis of the products in case of tetraaryl or aryl-alkyl mixed phosphonium salts only. In the former case, the lack of accuracy only afforded a broad idea of the relative anions stability [29, 30, 52] . In the latter, useful and accurate data were obtained about aryl anions basicity [36] . In this context, the present study attends to provide accurate data concerning the alkaline decomposition of tetraalkylphosphonium salts and the deduced kinetic basicities of primary, secondary and tertiary alkyl anions. Finally, the object of this present task is to propose a novel access to atropisomeric biphenylbisphosphine ligands for asymmetric catalysis. The first goal of this new synthetic approach is to provide a general method that allows easy tuning of the ligands produced. Having become readily accessible, 2,2',6,6'-tetrabromobiphenyl [ ] 53 appeared to be a judicious key intermediate. As a matter of fact, by taking advantage of the modern organometallic techniques developed and inspired by the recent work of F. Leroux [ ] 54 , it was possible to subject this substrate to successive permutational halogen/metal exchanges [45, 46] in order to allow diverse functionalizations.
7 At first, a double bromine/lithium permutation will be performed to produce the 2,2'- dilithiobiphenyl derivative which could be turned into the corresponding biphenol or diacid. Both axially chiral derivatives thus produced could then be resolved to afford pure enantiomers. The latter compounds, after few derivatization or protection steps could simply be converted to optically pure bisphosphines by reaction with an organolithium reagent and subsequent treatment with chlorodiphenylphosphine. R'' 2P R'' 2P R' R' R R' '' 2P R'' 2P R' 1) Metallation Br Br 2) I2 Br Br I 1) Derivatization 2) Br/Li permutation 3) ClPR'' 2 Br Br 1) Br/Li permutation 2) CuBr 2 3) PhNO 2 R R Racemate resolution Br R Br R Br Br Br Br Br R Br R R = OH, COOH 1) Br/Li permutation 2) functionalization In addition, the efficiency of the designed synthetic route relies on a crucial condition that had to be seriously taken into account. Hence, once produced, both pure atropisomers should be subjected to several chemical modifications without noticeable loss of their optical activity. For this reason, reaction conditions should be carefully chosen, especially for the last bromine/lithium permutation sequence which could possibly induce racemization. Indeed, though some calculations or experimental data were reported in the literature for binaphthyl cores [ 55 - 57 ] , only little information is available about rotational barrier of o,o'-dilithiobiphenyls [ , ] 58 59 . In this context, some of the lithiated biphenyls prepared will be used for dynamic NMR experiments in order to assess their rotational barrier. The value thus obtained, by comparison with those of the corresponding reduced parent compounds should provide helpful clues about the rotational stability of such species.
Page 1: Various Facets of Organophosphorus
Page 5: III Remerciements Je tiens à remer
Page 9: 3.3.6 Relevance of the Data Assesse
Page 13: VII Literature References 115 Compo
Page 17: IX Version Abrégée Les composés
Page 21 and 22: 1 Introduction 1 The present thesis
Page 23 and 24: 3 research groups in the field are
Page 25: 5 However, this mechanism suffers f
Page 30 and 31: 10 Although the most frequently emp
Page 32 and 33: 12 The preparation of the latter ph
Page 34 and 35: protected to its dioxolane derivati
Page 36 and 37: N (S)-14 1) NBS, THF, - 75 °C 2) -
Page 39 and 40: 3 Alkaline Decomposition of Phospho
Page 41 and 42: 3.2 Alkyl Carbanions Stabilities in
Page 43 and 44: 3.3.1 Mechanistic Discussion on the
Page 45 and 46: 25 The assumption reported by these
Page 47 and 48: 27 However, in the eventuality of a
Page 49 and 50: 29 To prepare tertiary phosphines b
Page 51 and 52: 31 Table 4. Mixed tertiary alkylpho
Page 53 and 54: 33 were comparable to those obtaine
Page 55 and 56: 35 led to the formation of di-tert-
Page 57 and 58: 37 depending on the alkyl substitue
Page 59 and 60: 39 4 A Novel Access to Atropisomeri
Page 61 and 62: 41 Since the homocoupling of the ha
Page 63 and 64: 43 Few other attempts to selectivel
Page 65 and 66: 45 The second phenol ether 36 was f
Page 67 and 68: 47 The enantiomeric purity was chec
Page 69 and 70: 49 A second purpose of this derivat
Page 71 and 72: 51 substrates considered. In conseq
Page 73 and 74: 53 Single-crystal X-ray analysis of
Page 75 and 76: 55 To convert atropisomer Ia into I
Page 77 and 78:
57 This finally allows one to use t
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the steric bulk and charge delocali
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61 To check the reproducibility of
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63 Figure 9. Full lineshape analysi
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66 suitably substituted dilithiobip
Page 89:
Experimental Part
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70 deuterochloroform (CDCl3) unless
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72 1 H NMR: δ = 7.32 (dddd, J = 9,
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1 H NMR: δ = 6.96 (s, 3 H), 6.94 (
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76 C21H21O9P (448.36) calcd. C 56.2
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78 C12H12BrN (250.13) calcd. C 57.6
Page 102 and 103:
80 C13H13NO2 (215.25) calcd. C 72.5
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82 3.1.1 Dialkyl-N,N-diethylaminoph
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84 apparatus. The solution was adde
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86 Di-tert-butylisopropylphosphine
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88 13 C NMR: δ = 32.9 (d, J = 12 H
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90 13 C NMR: δ = 41.5 (d, J = 61 H
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31 P NMR: δ = 53.4 ppm. 92 C16H31O
Page 116 and 117:
94 13 C NMR: δ = 40.8 (d, J = 3 Hz
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96 31 P NMR settings: It is known t
Page 120 and 121:
98 Theoretical ratio: (96.1:3.9) Ex
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101 4 The Preparation and Racemate
Page 125 and 126:
103 extraction protocol with ethyl
Page 127 and 128:
105 extracted with ethyl acetate (2
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107 (+)-(M)-Dimethyl-6,6’-dibromo
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109 (+)-(M)-2,2’-Dibromo-6,6’-b
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111 1 H NMR: δ = 7.2 (m, 20 H), 7.
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113 2,2’-Dilithio-6,6’-bis(meth
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References
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116 Conference Proceedings, Naples,
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118 [ 70] J. Drowart, C.E. Myers, R
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120 [117] S.T. Graul, R.R. Squires,
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122 [170] B.H. Lipshutz, F. Kayser,
Page 148:
124 [212] M. Schlosser, in Organome
Page 152:
O P 27i: p. 30, 80 C 9H 21OP P 26b:
Page 156:
P P P O 2: p. 11, 59 3 P O O O 11:
Page 160:
Nom Maurin Prénom Michaël 129 Cur
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