My PhD dissertation - Institut Fresnel

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66 suitably substituted dilithiobiphenyls and allowed rotational activation barrier to be calculated. Correlation of the results obtained with known literature data suggested a coordinative interaction between the lithium and oxygen atoms, causing a higher activation energy than envisioned. As a matter of fact, in both cases the free enthalpy values determined fell in the same range as those of bridged dilithiobiaryls, which supported the idea of an internal rigidity induced by the lithium-oxygen coordination. These assumptions should certainly be supported by a comparative study between the dilithiobiphenyls used and their metal-free congeners (H instead of Li). In the lithiated species, the two lithium atoms should logically tend to seek the proximity of the oxygens and coordinate them, causing a certain rigidity of the molecule. In contrast, it would be highly plausible that, in the metal-free congeners, no coordination, thus no additional constraints exist in the biphenyl unit. In this eventuality, the rotational activation barrier should be lower in the case of metal-free species, corroborating the proposed hypothesis. Other usefull informations could possibly be obtain by replacing the coordinating oxygens in the biphenyls used, by nitrogen or carbon atom. Finally, various phosphonium salts and phosphine oxides were prepared to address another field of application of organophosphorus compounds. These substrates served as probes for assessing relative stabilities of several alkyl carbanions. Based on the use of the alkaline decomposition of phosphonium salts, the method developed was meant to accurately determine differences in ease of cleavage between several alkyl substituents and was believed to directly correlate to their corresponding carbanions basicity. The data collected in this work provided unprecedented informations concerning secondary and tertiary alkyl carbanions in solution. When available, gas phase basicities of alkyl anions were compared to the results obtained by alkaline decomposition of phosphoniums salts. The relative stabilities observed in solution were coherent with the observed experimental reactivity but did parallel inverse order of the reported gas phase results, as one could expect. To provide a better overview on the factors influencing the alkaline decompositionof phosphonium salts, it would be interesting to perform other decompositions with phosphonium of the type RnR'pP + , X - where n and p would be varied. These experiments would hopefully allow an estimation of the effective importance of internal strains on the cleavage of the P–C bond from phosphonium salts.
67 If the ratio of the products formed does not appear to be depending on the substitution pattern, it would be legitimate to believe that the steric strains do not significantly influence the departure of a given substituent. In the latter hypothesis, and to provide a more complete overview of the alkyl carbanions basicities in solution, it would be useful to perform further experiments with phosphonium salts bearing very similar alkyl substituents, in order to build a "step by step" scale of basicity. On the other hand, since the alkaline decomposition of phosphonium salt appeared to be an effective method to assess the relative basicities of carbanionic species, it would be of interest to perform a systematic basicity assessment with several phosphonium halides bearing various substituted aryl groups. These results could then be correlated with those obtained for the same substrates, by means of other methods. For instance, the relative basicities of methoxy-, trifluoromethyl-, or haloarenes [ ] 220 determined with both methods, could be compared to evaluate the reliability of the values determined and the impact of solvents or aggregation effects. X' X OH P OH X' + O P X P O ∆G1 X ∆G2 X' X, X' = OCH 3, CF 3, F, Cl + X
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Various Facets of Organophosphorus
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III Remerciements Je tiens à remer
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3.3.6 Relevance of the Data Assesse
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VII Literature References 115 Compo
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IX Version Abrégée Les composés
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1 Introduction 1 The present thesis
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3 research groups in the field are
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5 However, this mechanism suffers f
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7 At first, a double bromine/lithiu
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10 Although the most frequently emp
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12 The preparation of the latter ph
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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
Page 79 and 80: the steric bulk and charge delocali
Page 81 and 82: 61 To check the reproducibility of
Page 83: 63 Figure 9. Full lineshape analysi
Page 89: Experimental Part
Page 92 and 93: 70 deuterochloroform (CDCl3) unless
Page 94 and 95: 72 1 H NMR: δ = 7.32 (dddd, J = 9,
Page 96 and 97: 1 H NMR: δ = 6.96 (s, 3 H), 6.94 (
Page 98 and 99: 76 C21H21O9P (448.36) calcd. C 56.2
Page 100 and 101: 78 C12H12BrN (250.13) calcd. C 57.6
Page 102 and 103: 80 C13H13NO2 (215.25) calcd. C 72.5
Page 104 and 105: 82 3.1.1 Dialkyl-N,N-diethylaminoph
Page 106 and 107: 84 apparatus. The solution was adde
Page 108 and 109: 86 Di-tert-butylisopropylphosphine
Page 110 and 111: 88 13 C NMR: δ = 32.9 (d, J = 12 H
Page 112 and 113: 90 13 C NMR: δ = 41.5 (d, J = 61 H
Page 114 and 115: 31 P NMR: δ = 53.4 ppm. 92 C16H31O
Page 116 and 117: 94 13 C NMR: δ = 40.8 (d, J = 3 Hz
Page 118 and 119: 96 31 P NMR settings: It is known t
Page 120 and 121: 98 Theoretical ratio: (96.1:3.9) Ex
Page 123 and 124: 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
Page 129 and 130: 107 (+)-(M)-Dimethyl-6,6’-dibromo
Page 131 and 132: 109 (+)-(M)-2,2’-Dibromo-6,6’-b
Page 133 and 134: 111 1 H NMR: δ = 7.2 (m, 20 H), 7.
Page 135 and 136: 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,
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124 [212] M. Schlosser, in Organome
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O P 27i: p. 30, 80 C 9H 21OP P 26b:
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P P P O 2: p. 11, 59 3 P O O O 11:
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Nom Maurin Prénom Michaël 129 Cur
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