My PhD dissertation - Institut Fresnel

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32 Table 5. Trialkylphosphine oxides R2R'P(O). Product R = R' = Yield 27a -C(CH3)3 -C4H9 87% 27b -C(CH3)3 -CH(CH3)2 88% 27c -C4H9 -CH2C(CH3)3 86% 27d -C4H9 -C(CH3)3 75% 27e -C2H5 -C4H9 78% [37] 27f -CH3 -C4H9 84% [38] 27g -C6H11 -C4H9 93% 27h -CH(CH3)2 -CH3 86% Other phosphine oxides needed as reference substances were prepared by means of known procedure from the literature. Thus, di-tert-butylmethylphosphine oxide (27i) was prepared by Michaelis-Arbuzov rearrangement of methyldi-tert-butylphosphinite [ ] 160 [ ] 161 [ ] 162 with iodomethane, whereas dibutylmethylphosphine oxide (27j) and tert-butyldimethylposphine oxide (27k) where obtained by reaction of butylmagnesium bromide or methylmagnesium bromide with methylphosphonic dichloride and tert-butylphosphonic dichloride respectively [ ] 163 . Finally, the quaternary phosphonium halides were obtained from mixed trialkyl phosphines 26a, 26c, 26d, and 26f by reaction with the appropriate alkyl halide in diethyl ether. The hygroscopic products were collected simple filtration under anhydrous conditions to give the starting phosphonium salts 28a - 28d (see § 3.3.4) which were further decomposed under alkaline conditions. 3.3.5 Alkaline Decomposition of Phosphonium Halides Several solvents, concentrations and water / solvent ratios were initially tried before optimum conditions have been found for the alkaline decomposition reaction. First of all, a dimethylsulfoxide/water mixture was chosen for the alkaline decomposition of dibutyldimethylphosphonium iodide (28a), di-tert-butyldimethylphosphonium iodide (28b) [ 164 ] and dibutyldi-tert-butylphosphonium iodide (28c) at 60 °C. The use of this polar aprotic solvent was mainly governed by its ability to enhance the nucleophilic activity of hydroxide ions to accelerate the reaction rate which is known to be relatively slow in the case of tetraalkylphosphonium salts [ , ] 165 166 . However, since the results collected in these conditions
33 were comparable to those obtained with a more classical butanol/water (8 : 2) mixture at 110 °C, and removal of the alcohol during work up was more convenient, this alcoholic reaction media was chosen instead. This study was not meant to be exhaustive but tried to select pertinent starting substrates which allowed the comparison of primary, secondary and tertiary alkyl anion stabilities in a systematic manner. Thus different primary alkyl carbanions were first compared with each other, by studying the alkaline decomposition of three tetraalkylphosphonium iodides bearing only primary alkyl groups. Decomposition of tributylneopentylphosphonium iodide (28d) in a butanol/water mixture with an excess of potassium hydroxide at 110 °C led to a mixture of tributylphosphine oxide and dibutylneopentylphosphine oxide in a 17 : 83 ratio. H9C4OH / H2O (8 : 2) P I P O + P O KOH, 110 °C 28d 17 : 83 + + This ratio, after statistical corrections, related to a relative rate constant k1/2 = 1.63 (±0.10) and revealed the butyl group to be cleaved more rapidly than its neopentyl congener with a difference in activation free enthalpy of ∆∆G ≠ = 0.37 (±0.06) kcal·mol -1 . On the basis of an expulsion governed by the relative stabilities of the corresponding carbanions expelled, this difference in energy was expected due to the presence of the strong electron releasing tertiary carbon center on the neopentyl groups. However, despite the presence of a tertiary electron releasing carbon on the neopentyl substituent, this value appeared to be relatively modest. More interestingly, when the two other phosphonium salts bearing four primary alkyl groups were decomposed, only one phosphine oxide was formed quantitatively in each case. As a matter of fact, when treated in alkaline conditions for 48 h at 110 °C, dibutyldimethylphosphonium iodide (28a) and butyltriethylphosphonium iodide (28e) gave only dibutylmethylphosphine oxide (27j) [162] and butyldiethylphosphine oxide (27e) [37] respectively. These results suggested that, within the limits of error in determination, the methyl and the ethyl substituents are more easily expelled than the butyl one with a difference of activation free enthalpy of ∆∆G ≠ > 4.60 kcal·mol -1 . 27c [ ] 167
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 and 26: 5 However, this mechanism suffers f
Page 27: 7 At first, a double bromine/lithiu
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: 31 Table 4. Mixed tertiary alkylpho
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 86 and 87: 66 suitably substituted dilithiobip
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
Page 137:
References
Page 140 and 141:
116 Conference Proceedings, Naples,
Page 142 and 143:
118 [ 70] J. Drowart, C.E. Myers, R
Page 144 and 145:
120 [117] S.T. Graul, R.R. Squires,
Page 146 and 147:
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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My PhD dissertation - Institut Fresnel

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