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34 Primary alkyl substituents were then compared to secondary ones by means of alkaline decomposition of two mixed phosphonium halides. Butyltricyclohexylphosphonium bromide (28f) was first decomposed under the usual butanol/water alkaline medium for 72 h at 110 °C to give a mixture of butyldicyclohexylphosphine oxide (27g) and tricyclohexylphosphine oxide in a 76 : 24 ratio. P 3 28f H 9C 4OH / H 2O (8 : 2) Br KOH, 110 °C P 2 O 27g + 76 : 24 + + Statistical corrections finally gave a relative rate constant of k1/2 = 1.02 (±0.06) which lead to a difference in activation free enthalpy of activation between cyclohexyl and butyl expulsion of ∆∆G ≠ ~ 0.0 kcal·mol -1 . Triisopropylmethylphoshonium iodide (28g) was then also submitted to the usual alkaline treatment but, in this case, triisopropylphosphine oxide was the sole product. This result, once again attested to the relatively large difference in activation free energy between methyl and other alkyl expulsion since it can be assumed that ∆∆G ≠ > 4.60 kcal·mol -1 . To assess the relative ease of alkyl cleavage between primary and tertiary groups, dibutyldi-tert-butylphosphonium iodide (28c) and di-tert-butyldimethylphosphonium iodide (28b) [164] were used as starting substrates. Phosphonium iodide 28c after alkaline decomposition gave a mixture of butyldi-tert-butylphosphine oxide (27a) and dibutyl-tert- butylphosphine oxide (27d) in a 97 : 3 ratio as revealed by 31 P NMR analysis. P I P O H9C4OH / H2O (8 : 2) 28c KOH, 110 °C O P 27a 27d 97 : 3 + + The relative rate constant k1/2 was in this of 30.8 (±3.90) and indicated a marked difference in promptness to form tert-butane and butane [∆∆G ≠ = 2.30 (±0.10) kcal·mol -1 ] even if alkaline decomposition gave rise to the formation of both possible phosphine oxides. Finally the alkaline decomposition of di-tert-butyldimethylphosphonium iodide (28b) [164] only + H P 3 O
35 led to the formation of di-tert-butylmethylphosphine oxide (27i) quantitatively. In view of these results, it it appears that methyl anion is formed more readily than tert-butyl anion (∆∆G ≠ > 4.6 kcal·mol -1 ). The last issue of this work was finally to compare the relative cleavage readiness between a secondary and a tertiary alkyl substituent. This was effectively assessed by decomposing tri-tert-butylisopropylphosphonium iodide (28h) under the same alkaline reaction conditions. The 31 P NMR analysis of the crude product mixture showed a 93 : 7 ratio of tri-tert- butylphosphine oxide and di-tert-butylisopropylphosphine oxide (27b) respectively. These products proportions gave a relative rate constant k1/2 = 4.68 (±0.09) which translated into a difference in activation free enthalpy between the formation of tert-butane and isopropane of ∆∆G ≠ = 1.18 (±0.08) kcal·mol -1 . In order to have a better overview on these results, the differences in activation free enthalpies, the results collected thus far are summarized in Figure 3. >4.60 1.18 (±0.08) 0.37(±0.06) ~0.0 C(CH 3) 3 CH(CH 3) 2 CH 2C(CH 3) 3 C 4H 9 C 2H 5 CH 3 2.30 (±0.10) >4.60 Figure 3. Relative ease of alkane formation determined by alkaline decomposition of phosphonium salts (∆∆G ≠ in kcal·mol -1 ). >4.60
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 and 52: 31 Table 4. Mixed tertiary alkylpho
Page 53: 33 were comparable to those obtaine
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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