"Front Matter". In: Organosilanes in Radical Chemistry - Index of

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Carbon–Carbon Double Bonds 91 (Z)-3-Hexen-1-ol, % 100 80 60 40 20 0 0 2 4 6 time, h 8 10 12 Figure 5.1 Reaction profile for the isomerization of (Z)-3-hexen-1-ol to (E)-3-hexen-1-ol and vice versa by (TMS) 3Si: radical in refluxing benzene degree of stabilization of the cyclohexadienyl-type radical rather than by polar effects. Kinetic studies have shown that all phenyl substituted silyl radicals can add to an aromatic ring of their precursor ( 10 6 M 1 s 1 ), in contrast with trialkylsilyl radicals which decay by combination–disproportionation reactions under similar conditions [24]. The reversibility has been studied in radical 3, generated from the corresponding cyclohexadiene and either photogenerated (0 8C) or thermally-generated (130 8C) t-BuO: radicals (Scheme 5.2). The elimination of Me3Si: radical is a primary step at high temperatures but unimportant at 0 8C [22]. This mechanistic concept has been used for designing a class of silylating agents, namely, silylated cyclohexadienes that will be further described in this chapter (see also Section 4.7). Me3Si SiMe3 t-BuO H H Me 3Si Me 3 Si 3 SiMe 3 H Scheme 5.2 Prove of the reversibility of the Me3Si: radical addition to substituted benzenes
92 Addition to Unsaturated Bonds 5.1.2 HYDROSILYLATION OF ALKENES Hydrosilylation of monosubstituted and gem-disubstituted olefins (Reactions 5.3 and 5.4) are efficient processes and have been shown to occur with high regioselectivity (anti-Markovnikov) in the case of both electron-rich and electron-poor olefins [25]. For cis or trans disubstituted double bonds, hydrosilylation is still an efficient process, although it requires slightly longer reaction times and an activating substituent (Reaction 5.5) [25]. Any hydrosilylation product has been observed with 1,2-dialkyl-and 1,2-diaryl-substituted olefins, due to the predominant reversible addition of (TMS) 3Si: radical to the double bond [19]. Me OBu CO 2Et Me CN (TMS) 3 SiH (TMS) 3Si AIBN, 80 �C OBu (5.3) (TMS) 3 SiH AIBN, 80 �C (TMS) 3 SiH AIBN, 80 �C 92% (TMS) 3Si (TMS) 3Si Me 77% CO 2Et The reversible addition of (TMS) 3Si: radical to the double bonds can be noteworthy also from a synthetic point of view. An example based on the isomerization of the industrially important 1,5,9-cyclododecatriene (4) is shown in Scheme 5.3 [19]. The final isomeric composition of 78:20:2 for (E,E,E)-4:(Z,E,E)-4:(Z,Z,E)-4, which is independent of the starting isomer or isomeric mixture, is reached in 5 h, by using (TMS) 3SiH=t-BuOOBu-t=143 8C and the yield is ca 80 %. (TMS) 3 Si (TMS) 3 Si 74% Me (E,E,E)-4 (Z,E,E)-4 (Z,Z,E)-4 Scheme 5.3 (Z)–(E) interconversion catalysed by (TMS) 3Si: radicals CN (5.4) (5.5)
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Organosilanes in Radical Chemistry
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DEDICATION To my parents XrZstoB an
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viii Contents 3.6 Hydrogen Atom: An
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PREFACE A large number of papers de
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ACKNOWLEDGEMENTS I thank Keith U. I
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2 Formation and Structures of Silyl
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10 Formation and Structures of Sily
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2 Thermochemistry 2.1 GENERAL CONSI
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Bond Dissociation Enthalpies 21 Tab
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Bond Dissociation Enthalpies 23 2.2
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Ion Thermochemistry 25 Table 2.4 Re
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Ion Thermochemistry 27 Table 2.5 El
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References 29 3. Goumri, A., Yuan,
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32 Hydrogen Donor Abilities of Sili
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Page 45 and 46: 38 Hydrogen Donor Abilities of Sili
Page 55 and 56: 4 Reducing Agents 4.1 GENERAL ASPEC
Page 57 and 58: General Aspects of Radical Chain Re
Page 59 and 60: Tris(trimethylsilyl)silane 53 Therm
Page 61 and 62: Tris(trimethylsilyl)silane 55 4.3.1
Page 63 and 64: Tris(trimethylsilyl)silane 57 A goo
Page 65 and 66: Tris(trimethylsilyl)silane 59 C(O)C
Page 67 and 68: Tris(trimethylsilyl)silane 61 radic
Page 69 and 70: Tris(trimethylsilyl)silane 63 86% y
Page 71 and 72: Tris(trimethylsilyl)silane 65 RO RO
Page 73 and 74: Tris(trimethylsilyl)silane 67 O AcO
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Page 77 and 78: Other Silicon Hydrides 71 The reduc
Page 79 and 80: Other Silicon Hydrides 73 The decre
Page 81 and 82: Other Silicon Hydrides 75 Ph MeS O
Page 83 and 84: Other Silicon Hydrides 77 Table 4.6
Page 85 and 86: Silicon Hydride / Thiol Mixture 79
Page 87 and 88: Silylated Cyclohexadienes 81 and (4
Page 89 and 90: References 83 34. Kawashima, E., Uc
Page 91 and 92: References 85 104. Gimisis, T., Bal
Page 93 and 94: 88 Addition to Unsaturated Bonds te
Page 95: 90 Addition to Unsaturated Bonds ap
Page 99 and 100: 94 Addition to Unsaturated Bonds R
Page 101 and 102: 96 Addition to Unsaturated Bonds Ph
Page 103 and 104: 98 Addition to Unsaturated Bonds EP
Page 105 and 106: 100 Addition to Unsaturated Bonds 5
Page 107 and 108: 102 Addition to Unsaturated Bonds T
Page 109 and 110: 104 Addition to Unsaturated Bonds R
Page 111 and 112: 106 Addition to Unsaturated Bonds a
Page 115 and 116: 110 Addition to Unsaturated Bonds S
Page 117 and 118: 112 Addition to Unsaturated Bonds T
Page 119 and 120: 114 Addition to Unsaturated Bonds I
Page 125 and 126: 120 Unimolecular Reactions 1 Si(H)M
Page 127 and 128: 122 Unimolecular Reactions t-Bu t-B
Page 129 and 130: 124 Unimolecular Reactions MeO Si O
Page 131 and 132: 126 Unimolecular Reactions t-Bu t-B
Page 133 and 134: 128 Unimolecular Reactions R 1 R 2
Page 135 and 136: 130 Unimolecular Reactions From the
Page 137 and 138: 132 Unimolecular Reactions rearrang
Page 139 and 140: 134 Unimolecular Reactions H 3 C +
Page 141 and 142: 136 Unimolecular Reactions Br O Si(
Page 143 and 144: 138 Unimolecular Reactions R3Si C C
Page 145 and 146: 140 Unimolecular Reactions Me3Si O
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142 Unimolecular Reactions 43. Albe
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144 Consecutive Radical Reactions c
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146 Consecutive Radical Reactions O
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148 Consecutive Radical Reactions a
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150 Consecutive Radical Reactions d
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152 Consecutive Radical Reactions T
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154 Consecutive Radical Reactions M
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156 Consecutive Radical Reactions F
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162 Consecutive Radical Reactions i
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164 Consecutive Radical Reactions A
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168 Consecutive Radical Reactions r
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170 Consecutive Radical Reactions E
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174 Consecutive Radical Reactions A
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176 Consecutive Radical Reactions P
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178 Consecutive Radical Reactions f
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182 Consecutive Radical Reactions 1
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184 Consecutive Radical Reactions 8
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186 Silyl Radicals in Polymers and
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220 List of Abbreviations PED photo
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222 Index Carbonyl sulfide 111 Carb
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224 Index Organosilicon boranes 2,
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226 Index Triethylsilane as mediato
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