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Silyl enol ether
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<h2 id="synthesis">Synthesis</h2> <p>Silyl enol ethers are generally prepared by reacting an enolizable <a href="/facts/Carbonyl_group/KJ71bo3X">carbonyl</a> compound with a silyl <a href="/facts/Electrophile/1AHFg1zm">electrophile</a> and a <a href="/facts/Base_(chemistry)/M9wA7qeM">base</a>, or just reacting an <a href="/facts/Enolate/D13WdFNR">enolate</a> with a silyl electrophile.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> Since silyl electrophiles are <a href="/facts/HSAB_theory/yguwscxc">hard</a> and silicon-oxygen bonds are very strong, the oxygen (of the carbonyl compound or enolate) acts as the <a href="/facts/Nucleophile/xYccoaJQ">nucleophile</a> to form a Si-O single bond.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> </p><p>The most commonly used silyl electrophile is <a href="/facts/Trimethylsilyl_chloride/CKlvuSgR">trimethylsilyl chloride</a>.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> To increase the rate of reaction, <a href="/facts/Trimethylsilyl_triflate/NhKjtHxd">trimethylsilyl triflate</a> may also be used in the place of trimethylsilyl chloride as a more electrophilic substrate.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a><a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> </p><p>When using an unsymmetrical enolizable carbonyl compound as a substrate, the choice of reaction conditions can help control whether the kinetic or thermodynamic silyl enol ether is preferentially formed.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> For instance, when using <a href="/facts/Lithium_diisopropylamide/5rcW8ERX">lithium diisopropylamide</a> (LDA), a strong and sterically hindered base, at low temperature (e.g., −78°C), the kinetic silyl enol ether (with a less substituted double bond) preferentially forms due to sterics.<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a><a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> When using <a href="/facts/Triethylamine/6DjzaGGv">triethylamine</a>, a weak base, the thermodynamic silyl enol ether (with a more substituted double bond) is preferred.<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a><a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a><a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> </p> <p>Alternatively, a rather exotic way of generating silyl enol ethers is via the <a href="/facts/Brook_rearrangement/FcKGXDxF">Brook rearrangement</a> of appropriate substrates.<a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a> </p> <h2 id="reactions">Reactions</h2> <h3>General reaction profile</h3> <p>Silyl enol ethers are neutral, mild nucleophiles (milder than <a href="/facts/Enamine/TaubsvCU">enamines</a>) that react with good electrophiles such as <a href="/facts/Aldehyde/xSIRkW03">aldehydes</a> (with <a href="/facts/Lewis_acid_catalysis/7q1hy6bQ">Lewis acid catalysis</a>) and <a href="/facts/Carbocation/vIggUxTh">carbocations</a>.<a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a><a class="footnote-ref" id="fnref:16" href="#fn:16"><sup>16</sup></a><a class="footnote-ref" id="fnref:17" href="#fn:17"><sup>17</sup></a><a class="footnote-ref" id="fnref:18" href="#fn:18"><sup>18</sup></a> Silyl enol ethers are stable enough to be isolated, but are usually used immediately after synthesis.<a class="footnote-ref" id="fnref:19" href="#fn:19"><sup>19</sup></a> </p> <h3>Generation of lithium enolate</h3> <p>Lithium enolates, one of the precursors to silyl enol ethers,<a class="footnote-ref" id="fnref:20" href="#fn:20"><sup>20</sup></a><a class="footnote-ref" id="fnref:21" href="#fn:21"><sup>21</sup></a> can also be generated from silyl enol ethers using <a href="/facts/Methyllithium/Fo5UzmsP">methyllithium</a>.<a class="footnote-ref" id="fnref:22" href="#fn:22"><sup>22</sup></a><a class="footnote-ref" id="fnref:23" href="#fn:23"><sup>23</sup></a> The reaction occurs via <a href="/facts/Nucleophilic_substitution/MLLeSsnr">nucleophilic substitution</a> at the silicon of the silyl enol ether, producing the lithium enolate and <a href="/facts/Tetramethylsilane/05nHMHJU">tetramethylsilane</a>.<a class="footnote-ref" id="fnref:24" href="#fn:24"><sup>24</sup></a><a class="footnote-ref" id="fnref:25" href="#fn:25"><sup>25</sup></a> </p> <h3>C–C bond formation</h3> <p>Silyl enol ethers are used in many reactions resulting in <a href="/facts/Alkylation/1rd5SNbt">alkylation</a>, e.g., <a href="/facts/Mukaiyama_aldol_addition/UzKe7pNh">Mukaiyama aldol addition</a>, <a href="/facts/Michael_reaction/yqLD22AQ">Michael reactions</a>, and Lewis-acid-catalyzed reactions with <a href="/facts/SN1_reaction/2myaFQEv">SN1</a>-reactive electrophiles (e.g., <a href="/facts/Tertiary_(chemistry)/2tdmz8wG">tertiary</a>, <a href="/facts/Allylic/CDxPwyvF">allylic</a>, or <a href="/facts/Benzylic/kHmqYwqH">benzylic</a> <a href="/facts/Alkyl_halides/Enb7LQqt">alkyl halides</a>).<a class="footnote-ref" id="fnref:26" href="#fn:26"><sup>26</sup></a><a class="footnote-ref" id="fnref:27" href="#fn:27"><sup>27</sup></a><a class="footnote-ref" id="fnref:28" href="#fn:28"><sup>28</sup></a><a class="footnote-ref" id="fnref:29" href="#fn:29"><sup>29</sup></a><a class="footnote-ref" id="fnref:30" href="#fn:30"><sup>30</sup></a> Alkylation of silyl enol ethers is especially efficient with tertiary alkyl halides, which form stable carbocations in the presence of Lewis acids like <a href="/facts/Titanium_tetrachloride/bGS32SsD">TiCl4</a> or <a href="/facts/Tin(IV)_chloride/MgGG3FJJ">SnCl4</a>.<a class="footnote-ref" id="fnref:31" href="#fn:31"><sup>31</sup></a> </p> <h3>Halogenation and oxidations</h3> <p>Halogenation of silyl enol ethers gives <a href="/facts/Haloketone/nR5a3YXD">haloketones</a>.<a class="footnote-ref" id="fnref:32" href="#fn:32"><sup>32</sup></a><a class="footnote-ref" id="fnref:33" href="#fn:33"><sup>33</sup></a> </p> <p><a href="/facts/Acyloin/Q9T0pL8T">Acyloins</a> form upon <a href="/facts/Organic_oxidation/6DdmXG4S">organic oxidation</a> with an electrophilic source of oxygen such as an <a href="/facts/Oxaziridine/Q8AIFVmY">oxaziridine</a> or <a href="/facts/MCPBA/xflsEmAN">mCPBA</a>.<a class="footnote-ref" id="fnref:34" href="#fn:34"><sup>34</sup></a> </p><p>In the <a href="/facts/Saegusa%E2%80%93Ito_oxidation/FUjXD2Yn">Saegusa–Ito oxidation</a>, certain silyl enol ethers are oxidized to <a href="/facts/Enone/gAflh5z4">enones</a> with <a href="/facts/Palladium(II)_acetate/LyGTuTVF">palladium(II) acetate</a>. </p> <h3>Sulfenylation</h3> <p>Reacting a silyl enol ether with PhSCl, a good and soft electrophile, provides a carbonyl compound sulfenylated at an <a href="/facts/Alpha_carbon/E44SeQ1L">alpha carbon</a>.<a class="footnote-ref" id="fnref:35" href="#fn:35"><sup>35</sup></a><a class="footnote-ref" id="fnref:36" href="#fn:36"><sup>36</sup></a> In this reaction, the <a href="/facts/Trimethylsilyl/RJuCYXfk">trimethylsilyl</a> group of the silyl enol ether is removed by the <a href="/facts/Chloride/m9NUaUDR">chloride</a> ion released from the PhSCl upon attack of its electrophilic sulfur atom.<a class="footnote-ref" id="fnref:37" href="#fn:37"><sup>37</sup></a> </p> <h3>Hydrolysis</h3> <p><a href="/facts/Hydrolysis/JTvwIHPs">Hydrolysis</a> of a silyl enol ether results in the formation of a carbonyl compound and a <a href="/facts/Disiloxane/vpfSHDBq">disiloxane</a>.<a class="footnote-ref" id="fnref:38" href="#fn:38"><sup>38</sup></a><a class="footnote-ref" id="fnref:39" href="#fn:39"><sup>39</sup></a> In this reaction, water acts as an oxygen nucleophile and attacks the silicon of the silyl enol ether.<a class="footnote-ref" id="fnref:40" href="#fn:40"><sup>40</sup></a> This leads to the formation of the carbonyl compound and a <a href="/facts/Trimethylsilanol/N9czlqxt">trimethylsilanol</a> intermediate that undergoes nucleophilic substitution at silicon (by another trimethylsilanol) to give the disiloxane.<a class="footnote-ref" id="fnref:41" href="#fn:41"><sup>41</sup></a> </p> <h3>Ring contraction</h3> <p>Cyclic silyl enol ethers undergo regiocontrolled one-carbon ring contractions.<a class="footnote-ref" id="fnref:42" href="#fn:42"><sup>42</sup></a><a class="footnote-ref" id="fnref:43" href="#fn:43"><sup>43</sup></a> These reactions employ electron-deficient sulfonyl azides, which undergo chemoselective, uncatalyzed [3+2] cycloaddition to the silyl enol ether, followed by loss of dinitrogen, and alkyl migration to give ring-contracted products in good yield. These reactions may be directed by substrate stereochemistry, giving rise to stereoselective ring-contracted product formation. </p> <h2 id="silyl-ketene-acetals">Silyl ketene acetals</h2> <p>Silyl enol ethers of <a href="/facts/Ester/FoUAIIw4">esters</a> (−OR) or <a href="/facts/Carboxylic_acid/U4xuMosy">carboxylic acids</a> (−COOH) are called silyl ketene acetals<a class="footnote-ref" id="fnref:44" href="#fn:44"><sup>44</sup></a> and have the general structure R3Si−O−C(OR)=CR2. These compounds are more nucleophilic than the silyl enol ethers of <a href="/facts/Ketone/BqQXpLo4">ketones</a> (>C=O).<a class="footnote-ref" id="fnref:45" href="#fn:45"><sup>45</sup></a> </p> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Peter Brownbridge (1983). "Silyl Enol Ethers in Synthesis - Part I". Synthesis. 1983: 1–28. doi:10.1055/s-1983-30204. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Ian Fleming (2007). "A Primer on Organosilicon Chemistry". Ciba Foundation Symposium 121 - Silicon Biochemistry. Novartis Foundation Symposia. Vol. 121. Wiley. pp. 112–122. doi:10.1002/9780470513323.ch7. ISBN 978-0-470-51332-3. PMID 3743226. <a href="978-0-470-51332-3" target="_blank">978-0-470-51332-3</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Clayden, J., Greeves, N., & Warren, S. (2012). Silyl enol ethers. In Organic chemistry (Second ed., pp. 466-467). Oxford University Press. <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Clayden, J., Greeves, N., & Warren, S. (2012). Silyl enol ethers. In Organic chemistry (Second ed., pp. 466-467). Oxford University Press. <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Clayden, J., Greeves, N., & Warren, S. (2012). Silyl enol ethers. In Organic chemistry (Second ed., pp. 466-467). Oxford University Press. <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Clayden, J., Greeves, N., & Warren, S. (2012). Nucleophilic substitution at silicon. In Organic chemistry (Second ed., pp. 669-670). Oxford University Press. <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>Jung, M. E., & Perez, F. (2009). Synthesis of 2-Substituted 7-Hydroxybenzofuran-4-carboxylates via Addition of Silyl Enol Ethers to o -Benzoquinone Esters. Organic Letters, 11(10), 2165–2167. doi:10.1021/ol900416x <a href="//doi.org/10.1021/ol900416x" target="_blank">//doi.org/10.1021/ol900416x</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Chan, T.-H. (1991). Formation and Addition Reactions of Enol Ethers. In Comprehensive Organic Synthesis (pp. 595–628). Elsevier. doi:10.1016/B978-0-08-052349-1.00042-1 <a href="//doi.org/10.1016/B978-0-08-052349-1.00042-1" target="_blank">//doi.org/10.1016/B978-0-08-052349-1.00042-1</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>Chan, T.-H. (1991). Formation and Addition Reactions of Enol Ethers. In Comprehensive Organic Synthesis (pp. 595–628). Elsevier. doi:10.1016/B978-0-08-052349-1.00042-1 <a href="//doi.org/10.1016/B978-0-08-052349-1.00042-1" target="_blank">//doi.org/10.1016/B978-0-08-052349-1.00042-1</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>Clayden, J., Greeves, N., & Warren, S. (2012). Kinetically controlled enolate formation. In Organic chemistry (Second ed., pp. 600-601). Oxford University Press. <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>Chan, T.-H. (1991). Formation and Addition Reactions of Enol Ethers. In Comprehensive Organic Synthesis (pp. 595–628). Elsevier. doi:10.1016/B978-0-08-052349-1.00042-1 <a href="//doi.org/10.1016/B978-0-08-052349-1.00042-1" target="_blank">//doi.org/10.1016/B978-0-08-052349-1.00042-1</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>Clayden, J., Greeves, N., & Warren, S. (2012). Thermodynamically controlled enolate formation. In Organic chemistry (Second ed., pp. 599-600). Oxford University Press. <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>Clayden, J., Greeves, N., & Warren, S. (2012). Making the more substituted enolate equivalent: thermodynamic enolates. In Organic chemistry (Second ed., p. 636). Oxford University Press. <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> <li id="fn:14"><p>Clive, Derrick L. J. & Sunasee, Rajesh (2007). "Formation of Benzo-Fused Carbocycles by Formal Radical Cyclization onto an Aromatic Ring". Org. Lett. 9 (14): 2677–2680. doi:10.1021/ol070849l. PMID 17559217. <a href="/wiki/Organic_Letters" target="_blank">/wiki/Organic_Letters</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></p></li> <li id="fn:15"><p>Clayden, J., Greeves, N., & Warren, S. (2012). Silyl enol ethers in aldol reactions. In Organic chemistry (Second ed., pp. 626-627). Oxford University Press. <a href="#fnref:15" class="footnote-back-ref">↩</a></p></li> <li id="fn:16"><p>Clayden, J., Greeves, N., & Warren, S. (2012). Silyl enol ethers are alkylated by SN1-reactive electrophiles in the presence of Lewis acid. In Organic chemistry (Second ed., p. 595). Oxford University Press. <a href="#fnref:16" class="footnote-back-ref">↩</a></p></li> <li id="fn:17"><p>Clayden, J., Greeves, N., & Warren, S. (2012). Conjugate addition of silyl enol ethers leads to the silyl enol ether of the product. In Organic chemistry (Second ed., pp. 608-609). Oxford University Press. <a href="#fnref:17" class="footnote-back-ref">↩</a></p></li> <li id="fn:18"><p>Quirk, R.P., & Pickel, D.L. (2012). Silyl enol ethers. In Controlled end-group functionalization (including telechelics) (pp. 405-406). Elsevier. doi:10.1016/B978-0-444-53349-4.00168-0 <a href="//doi.org/10.1016/B978-0-444-53349-4.00168-0" target="_blank">//doi.org/10.1016/B978-0-444-53349-4.00168-0</a> <a href="#fnref:18" class="footnote-back-ref">↩</a></p></li> <li id="fn:19"><p>Clayden, J., Greeves, N., & Warren, S. (2012). Silyl enol ethers in aldol reactions. In Organic chemistry (Second ed., pp. 626-627). Oxford University Press. <a href="#fnref:19" class="footnote-back-ref">↩</a></p></li> <li id="fn:20"><p>Chan, T.-H. (1991). Formation and Addition Reactions of Enol Ethers. In Comprehensive Organic Synthesis (pp. 595–628). Elsevier. doi:10.1016/B978-0-08-052349-1.00042-1 <a href="//doi.org/10.1016/B978-0-08-052349-1.00042-1" target="_blank">//doi.org/10.1016/B978-0-08-052349-1.00042-1</a> <a href="#fnref:20" class="footnote-back-ref">↩</a></p></li> <li id="fn:21"><p>Clayden, J., Greeves, N., & Warren, S. (2012). Kinetically controlled enolate formation. In Organic chemistry (Second ed., pp. 600-601). Oxford University Press. <a href="#fnref:21" class="footnote-back-ref">↩</a></p></li> <li id="fn:22"><p>House, H. O., Gall, M., & Olmstead, H. D. (1971). Chemistry of carbanions. XIX. Alkylation of enolates from unsymmetrical ketones. The Journal of Organic Chemistry, 36(16), 2361–2371. doi:10.1021/jo00815a037 <a href="//doi.org/10.1021/jo00815a037" target="_blank">//doi.org/10.1021/jo00815a037</a> <a href="#fnref:22" class="footnote-back-ref">↩</a></p></li> <li id="fn:23"><p>Clayden, J., Greeves, N., & Warren, S. (2012). Silyl enol ethers. In Organic chemistry (Second ed., pp. 466-467). Oxford University Press. <a href="#fnref:23" class="footnote-back-ref">↩</a></p></li> <li id="fn:24"><p>House, H. O., Gall, M., & Olmstead, H. D. (1971). Chemistry of carbanions. XIX. Alkylation of enolates from unsymmetrical ketones. The Journal of Organic Chemistry, 36(16), 2361–2371. doi:10.1021/jo00815a037 <a href="//doi.org/10.1021/jo00815a037" target="_blank">//doi.org/10.1021/jo00815a037</a> <a href="#fnref:24" class="footnote-back-ref">↩</a></p></li> <li id="fn:25"><p>Clayden, J., Greeves, N., & Warren, S. (2012). Silyl enol ethers. In Organic chemistry (Second ed., pp. 466-467). Oxford University Press. <a href="#fnref:25" class="footnote-back-ref">↩</a></p></li> <li id="fn:26"><p>Matsuo, J., & Murakami, M. (2013). The Mukaiyama Aldol Reaction: 40 Years of Continuous Development. Angewandte Chemie International Edition, 52(35), 9109–9118. doi:10.1002/anie.201303192 <a href="//doi.org/10.1002/anie.201303192" target="_blank">//doi.org/10.1002/anie.201303192</a> <a href="#fnref:26" class="footnote-back-ref">↩</a></p></li> <li id="fn:27"><p>Narasaka, K., Soai, K., Aikawa, Y., & Mukaiyama, T. (1976). The Michael Reaction of Silyl Enol Ethers with α, β-Unsaturated Eetones and Acetals in the Presence of Titanium Tetraalkoxide and Titanium Tetrachloride. Bulletin of the Chemical Society of Japan, 49(3), 779-783. doi:10.1246/bcsj.49.779 <a href="//doi.org/10.1246/bcsj.49.779" target="_blank">//doi.org/10.1246/bcsj.49.779</a> <a href="#fnref:27" class="footnote-back-ref">↩</a></p></li> <li id="fn:28"><p>M. T. Reetz & A. Giannis (1981) Lewis Acid Mediated α-Thioalkylation of Ketones, Synthetic Communications, 11:4, 315-322, doi:10.1080/00397918108063611 <a href="//doi.org/10.1080/00397918108063611" target="_blank">//doi.org/10.1080/00397918108063611</a> <a href="#fnref:28" class="footnote-back-ref">↩</a></p></li> <li id="fn:29"><p>Clayden, J., Greeves, N., & Warren, S. (2012). Conjugate addition of silyl enol ethers leads to the silyl enol ether of the product. In Organic chemistry (Second ed., pp. 608-609). Oxford University Press. <a href="#fnref:29" class="footnote-back-ref">↩</a></p></li> <li id="fn:30"><p>Clayden, J., Greeves, N., & Warren, S. (2012). Silyl enol ethers are alkylated by SN1-reactive electrophiles in the presence of Lewis acid. In Organic chemistry (Second ed., p. 595). Oxford University Press. <a href="#fnref:30" class="footnote-back-ref">↩</a></p></li> <li id="fn:31"><p>Clayden, J., Greeves, N., & Warren, S. (2012). Silyl enol ethers are alkylated by SN1-reactive electrophiles in the presence of Lewis acid. In Organic chemistry (Second ed., p. 595). Oxford University Press. <a href="#fnref:31" class="footnote-back-ref">↩</a></p></li> <li id="fn:32"><p>Teruo Umemoto; Kyoichi Tomita; Kosuke Kawada (1990). "N-Fluoropyridinium Triflate: An Electrophilic Fluorinating Agent". Organic Syntheses. 69: 129. doi:10.1002/0471264180.os069.16. ISBN 0-471-26422-9. <a href="0-471-26422-9" target="_blank">0-471-26422-9</a> <a href="#fnref:32" class="footnote-back-ref">↩</a></p></li> <li id="fn:33"><p>Clayden, J., Greeves, N., & Warren, S. (2012). Reactions of silyl enol ethers with halogen and sulfur electrophiles. In Organic chemistry (Second ed., pp. 469-470). Oxford University Press. <a href="#fnref:33" class="footnote-back-ref">↩</a></p></li> <li id="fn:34"><p>Organic Syntheses, Coll. Vol. 7, p.282 (1990); Vol. 64, p.118 (1986) Article. <a href="/wiki/Organic_Syntheses" target="_blank">/wiki/Organic_Syntheses</a> <a href="#fnref:34" class="footnote-back-ref">↩</a></p></li> <li id="fn:35"><p>Chibale, K., & Warren, S. (1996). Kinetic resolution in asymmetric anti aldol reactions of branched and straight chain racemic 2-phenylsulfanyl aldehydes: asymmetric synthesis of cyclic ethers and lactones by phenylsulfanyl migration. Journal of the Chemical Society, Perkin Transactions 1, (16), 1935-1940. doi:10.1039/P19960001935 <a href="//doi.org/10.1039/P19960001935" target="_blank">//doi.org/10.1039/P19960001935</a> <a href="#fnref:35" class="footnote-back-ref">↩</a></p></li> <li id="fn:36"><p>Clayden, J., Greeves, N., & Warren, S. (2012). Reactions of silyl enol ethers with halogen and sulfur electrophiles. In Organic chemistry (Second ed., pp. 469-470). Oxford University Press. <a href="#fnref:36" class="footnote-back-ref">↩</a></p></li> <li id="fn:37"><p>Clayden, J., Greeves, N., & Warren, S. (2012). Reactions of silyl enol ethers with halogen and sulfur electrophiles. In Organic chemistry (Second ed., pp. 469-470). Oxford University Press. <a href="#fnref:37" class="footnote-back-ref">↩</a></p></li> <li id="fn:38"><p>Clayden, J., Greeves, N., & Warren, S. (2012). Hydrolysis of enol ethers. In Organic chemistry (Second ed., pp. 468-469). Oxford University Press. <a href="#fnref:38" class="footnote-back-ref">↩</a></p></li> <li id="fn:39"><p>Gupta, S. K., Sargent, J. R., & Weber, W. P. (2002). Synthesis and photo-oxidative degradation of 2, 6-bis-[ω-trimethylsiloxypolydimethylsiloxy-2′-dimethylsilylethyl] acetophenone. Polymer, 43(1), 29-35. doi:10.1016/S0032-3861(01)00602-4 <a href="//doi.org/10.1016/S0032-3861(01)00602-4" target="_blank">//doi.org/10.1016/S0032-3861(01)00602-4</a> <a href="#fnref:39" class="footnote-back-ref">↩</a></p></li> <li id="fn:40"><p>Clayden, J., Greeves, N., & Warren, S. (2012). Hydrolysis of enol ethers. In Organic chemistry (Second ed., pp. 468-469). Oxford University Press. <a href="#fnref:40" class="footnote-back-ref">↩</a></p></li> <li id="fn:41"><p>Clayden, J., Greeves, N., & Warren, S. (2012). Hydrolysis of enol ethers. In Organic chemistry (Second ed., pp. 468-469). Oxford University Press. <a href="#fnref:41" class="footnote-back-ref">↩</a></p></li> <li id="fn:42"><p>(a) Wohl, R. Helv. Chim. Acta 1973, 56, 1826. (b) Xu, Y. Xu, G.; Zhu, G.; Jia, Y.; Huang, Q. J. Fluorine Chem. 1999, 96, 79. <a href="#fnref:42" class="footnote-back-ref">↩</a></p></li> <li id="fn:43"><p>Mitcheltree, M. J.; Konst, Z. A.; Herzon, S. B. Tetrahedron 2013, 69, 5634. <a href="#fnref:43" class="footnote-back-ref">↩</a></p></li> <li id="fn:44"><p>Clayden, J., Greeves, N., & Warren, S. (2012). Conjugate addition of silyl enol ethers leads to the silyl enol ether of the product. In Organic chemistry (Second ed., pp. 608-609). Oxford University Press. <a href="#fnref:44" class="footnote-back-ref">↩</a></p></li> <li id="fn:45"><p>Clayden, J., Greeves, N., & Warren, S. (2012). Conjugate addition of silyl enol ethers leads to the silyl enol ether of the product. In Organic chemistry (Second ed., pp. 608-609). Oxford University Press. <a href="#fnref:45" class="footnote-back-ref">↩</a></p></li> </ol>