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

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Allylations 173 Y R 3 Si R R 3 SiZ Y R R 3Si R 3 Si Scheme 7.8 Propagation steps for allylation reaction using allylsilanes (Reaction 7.74) [84]. That is, (TMS) 3Si: radical added to the double bond of allyl sulfides, giving rise to a radical intermediate that undergoes b-scission with the ejection of the thiyl radical. Hydrogen abstraction from the silane completes the cycle of these chain reactions. 2-Functionalized allyl tris(trimethylsilyl)silanes (71) have been employed in the radical-based allylation reactions. Z SPh Z = H, Me, Cl, CN, CO 2Et (TMS) 3 SiH AIBN, 80 �C RZ Y R Z (TMS) 3Si + PhSH 71, 79-92% (7.74) Radical allylations with allylsilanes 71 occur under mild conditions in good to excellent yields, provided that the radical precursor and the silane have the appropriate electronic pairing [85]. The two examples in Reactions (7.75) and (7.76) show the reactivity matching of the allylating agent with the radical. These reactions offer tin-free alternatives for the transformations that are currently carried out by allyl stannanes. (TMS) 3 Si (TMS) 3 Si Me CO 2 Et + + O O Br O AIBN O 80 �C Me t-BuOOBu-t 84% CO2Et I 140 �C 89% (7.75) (7.76)
174 Consecutive Radical Reactions Allylsilylation procedures of carbon–carbon and carbon–oxygen double bonds under free-radical conditions have been established [86]. For example the reaction of 72 with a variety of monosubstituted alkenes (R ¼ CN, CO2 Me, Ph, n-C8H 17, OBu, SPh) gives the corresponding allylsilylated products in moderate to very good yields, whereas with maleic anhydrides high stereoselectivity was observed. This methodology is also applicable to carbonyl derivatives (Scheme 7.9). Similar experiments have been performed by replacing alkenes with alkynes and the formation of bisallylic derivatives has been reported. (TMS) 3 Si R R CO 2 Me 44-91% (TMS) 3 Si O Ph H (TMS) 3 Si O 72 CO 2 Me Ph CO 2 Me 81% Scheme 7.9 Allysilylation of unsaturated bonds O O R O O (TMS) 3 Si 7.7 APPLICATION TO TANDEM AND CASCADE RADICAL REACTIONS O R O CO 2 Me R = H, 89% R = Me, 58% The increasing popularity of radical reactions is certainly due to the so-called ‘tandem or cascade reaction’, i.e., the ability of forming and breaking several bonds in a one-pot procedure. Again, the concepts of disciplined processes and predictability are applied in these successful strategies, which show the elegance and power of the synthetic plan based on radical reactions. Two examples of three-components coupling reaction are shown in Reactions (7.77) and (7.78) [27,87]. These radical chain reactions proceeded by the addition of an alkyl or vinyl radical onto carbon monoxide, generating an acyl radical intermediate, which, in turn, can further react with electron-deficient olefins to lead, after reduction, to a formal double alkylation of carbon monoxide. These three-components coupling reactions require the generation of four highly disciplined radical species, which have specific functions during the chain reaction.
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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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4 Reducing Agents 4.1 GENERAL ASPEC
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General Aspects of Radical Chain Re
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Tris(trimethylsilyl)silane 53 Therm
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Tris(trimethylsilyl)silane 55 4.3.1
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Tris(trimethylsilyl)silane 57 A goo
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Tris(trimethylsilyl)silane 59 C(O)C
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Tris(trimethylsilyl)silane 61 radic
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Tris(trimethylsilyl)silane 63 86% y
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Tris(trimethylsilyl)silane 65 RO RO
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Tris(trimethylsilyl)silane 67 O AcO
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Tris(trimethylsilyl)silane 69 Tris(
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Other Silicon Hydrides 71 The reduc
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Other Silicon Hydrides 73 The decre
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Other Silicon Hydrides 75 Ph MeS O
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Other Silicon Hydrides 77 Table 4.6
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Silicon Hydride / Thiol Mixture 79
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Silylated Cyclohexadienes 81 and (4
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References 83 34. Kawashima, E., Uc
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References 85 104. Gimisis, T., Bal
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88 Addition to Unsaturated Bonds te
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90 Addition to Unsaturated Bonds ap
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92 Addition to Unsaturated Bonds 5.
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94 Addition to Unsaturated Bonds R
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96 Addition to Unsaturated Bonds Ph
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98 Addition to Unsaturated Bonds EP
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100 Addition to Unsaturated Bonds 5
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102 Addition to Unsaturated Bonds T
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104 Addition to Unsaturated Bonds R
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106 Addition to Unsaturated Bonds a
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110 Addition to Unsaturated Bonds S
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112 Addition to Unsaturated Bonds T
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114 Addition to Unsaturated Bonds I
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120 Unimolecular Reactions 1 Si(H)M
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Page 129 and 130: 124 Unimolecular Reactions MeO Si O
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Page 143 and 144: 138 Unimolecular Reactions R3Si C C
Page 145 and 146: 140 Unimolecular Reactions Me3Si O
Page 147 and 148: 142 Unimolecular Reactions 43. Albe
Page 149 and 150: 144 Consecutive Radical Reactions c
Page 151 and 152: 146 Consecutive Radical Reactions O
Page 153 and 154: 148 Consecutive Radical Reactions a
Page 155 and 156: 150 Consecutive Radical Reactions d
Page 157 and 158: 152 Consecutive Radical Reactions T
Page 159 and 160: 154 Consecutive Radical Reactions M
Page 161 and 162: 156 Consecutive Radical Reactions F
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Page 169 and 170: 164 Consecutive Radical Reactions A
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Page 187 and 188: 182 Consecutive Radical Reactions 1
Page 189 and 190: 184 Consecutive Radical Reactions 8
Page 191 and 192: 186 Silyl Radicals in Polymers and
Page 225 and 226: 220 List of Abbreviations PED photo
Page 227 and 228: 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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