Propellane

<h2 id="nomenclature">Nomenclature</h2>

The name derives from a supposed resemblance of the molecule to a <a href="/facts/Propeller/0IN0JKXC">propeller</a>: namely, the rings would be the propeller's blades, and the shared C–C bond would be its axis. The bond shared by the three cycles is usually called the "bridge"; the shared carbon atoms are then the "bridgeheads".
The IUPAC nomenclature of the homologue series of all-carbon propellanes would be called tricyclo[x.y.z.01,(x+2)]alkane. More common in literature is the notation [x.y.z]propellane means the member of the family whose rings have x, y, and z carbons, not counting the two bridgeheads; or x + 2, y + 2, and z + 2 carbons, counting them. The chemical formula is therefore C2+x+y+zH2(x+y+z). The minimum value for x, y, and z is 1, meaning three fused cyclopropyl-rings forming the [1.1.1]propellane. There is no structural ordering between the rings; for example, [1.3.2]propellane is the same substance as [3.2.1]propellane. Therefore, it is customary to sort the indices in decreasing order, x ≥ y ≥ z.
Further, heterosubstituted propellanes or structurally embedded propellane moieties exist and have been synthesised and follow a more complex nomenclature (see below).

<h2 id="general-properties">General properties</h2>
<h3>Strain</h3>
Propellanes with small cycles, such as <a href="/facts/1.1.1-Propellane/L6sPCqg0">[1.1.1]propellane</a> or <a href="/facts/2.2.2-Propellane/B33lT9da">[2.2.2]propellane</a>, bear a high absolute strain energy. The two interbridgeheaded carbons have an <a href="/facts/Inverted_tetrahedral_geometry/583AL1sP">inverted tetrahedral geometry</a>.

Computed Strain energies of Propellanes<a class="footnote-ref" id="fnref:5" href="#fn:5">5</a><table><tbody><tr><th>Propellane</th><th>Strain energy</th></tr><tr><td>[1.1.1]Propellane</td><td>98 kcal mol−1</td></tr><tr><td>[3.1.1]Propellane</td><td>76 kcal mol−1</td></tr><tr><td>[2.1.1]Propellane</td><td>86 kcal mol−1</td></tr><tr><td>[2.2.1]Propellane</td><td>82 kcal mol−1</td></tr><tr><td>[3.2.1]Propellane</td><td>67 kcal mol−1</td></tr></tbody></table>
The resulting strain causes such compounds to be unstable and highly reactive. The interbridgehead C-C bond is easily broken (even spontaneously) to yield less-strained bicyclic or even monocyclic hydrocarbons. This so-called strain-release chemistry is used in strategies to access otherwise hard-to-obtain structures.
Surprisingly, the most strained member [1.1.1] is far more stable than the other small ring members ([2.1.1], [2.2.1], [2.2.2], [3.2.1], [3.1.1], and [4.1.1]),<a class="footnote-ref" id="fnref:6" href="#fn:6">6</a> which can be explained by special bonding situation of the interbridgehead bond.

<h3>Bonding properties</h3>
The bonding situation of small-ring propellanes, such as [n.1.1]propellanes, is topic of debate. Recent computational studies explain the interbridgehead bond as a <a href="/facts/Charge-shift_bond/T4g4kdjy">Charge-shift bond</a> possessing an unusual positive <a href="/facts/Laplace_operator/kov9u3PT">Laplace operator</a> 
 
 
 
 
 ∇
 
 2
 
 
 
 
 {\displaystyle \nabla ^{2}}
 
 of the electron density 
 
 
 
 ρ
 
 
 {\displaystyle \rho }
 
.<a class="footnote-ref" id="fnref:7" href="#fn:7">7</a> Studies by Sterling et al. suggest delocalisation effects onto the three-membered bridges relaxing Pauli-repulsion and thus stabilising the propellane core.<a class="footnote-ref" id="fnref:8" href="#fn:8">8</a>

<h3>Reactivity</h3>
Propellanes, especially the synthetically studied [1.1.1]Propellane, is known to possess omniphilic reactivity. Anions and radicals add towards the interbridgehead bond resulting in bicyclo[1.1.1]pentyl-units. In contrary, cations and metals decompose the tricyclic core towards monocyclic systems by opening of the bridged bonds forming exo-methylene cyclobutanes.<a class="footnote-ref" id="fnref:9" href="#fn:9">9</a> For [3.1.1]propellane only radical addition is reported.<a class="footnote-ref" id="fnref:10" href="#fn:10">10</a><a class="footnote-ref" id="fnref:11" href="#fn:11">11</a> The reactivity of other propellanes is far less explored and their reactivity profile is less clear.

<h3>Polymerization</h3>
In principle, any propellane can be <a href="/facts/Polymer/eF32E50K">polymerized</a> by breaking the axial C–C bond to yield a <a href="/facts/Radical_(chemistry)/qFymuVoT">radical</a> with two active centers, and then joining these radicals in a linear chain. For the propellanes with small cycles (such as [1.1.1], [3.2.1], or 1,3-dihydroadamantane), this process is easily achieved, yielding either simple polymers or <a href="/facts/Alternating_polymer/35D97DuV">alternating copolymers</a>. For example, [1.1.1]propellane yields spontaneously an interesting rigid polymer called <a href="/facts/Staffane/23qvIYQx">staffane</a>;<a class="footnote-ref" id="fnref:12" href="#fn:12">12</a> and [3.2.1]propellane combines spontaneously with oxygen at room temperature to give a copolymer where the bridge-opened propellane units [–C8H12–] alternate with [–O–O–] groups.<a class="footnote-ref" id="fnref:13" href="#fn:13">13</a>

<h3>Synthesis</h3>
The smaller-cycle propellanes are difficult to synthesize because of their strain. Larger members are more easily obtained. Weber and Cook described in 1978 a general method which should yield [n.3.3]propellanes for any n ≥ 3.<a class="footnote-ref" id="fnref:14" href="#fn:14">14</a>

<h2 id="members">Members</h2>
<h3>True propellanes</h3>
<ul><li><a href="/facts/1.1.1-Propellane/L6sPCqg0">[1.1.1]Propellane</a>, C5H6, <a href="/facts/CAS_number/zjXjCGPx">CAS number</a> <a href="https://commonchemistry.cas.org/detail?cas_rn=35634-10-7&title=">35634-10-7</a> (<a href="/facts/Kenneth_B._Wiberg/QU5TuSye">K. Wiberg</a> and F. Walker, 1982).<a class="footnote-ref" id="fnref:15" href="#fn:15">15</a> It is a highly strained molecule: the two central carbons have an inverted tetrahedron geometry, and each of the three cycles is the notoriously strained <a href="/facts/Cyclopropane/BAUAYB7s">cyclopropane</a> ring. The <a href="/facts/Bond_length/rHHIBH6q">length of the central bond</a> is only 160 pm. It is an unstable product that undergoes thermal <a href="/facts/Isomerization/sxv23uKl">isomerization</a> to 3-methylene<a href="/facts/Cyclobutene/FKF1XqKh">cyclobutene</a> at 114 °C,and spontaneously reacts with <a href="/facts/Acetic_acid/uyBKA2Pd">acetic acid</a> to form a methylenecyclobutane <a href="/facts/Ester/FoUAIIw4">ester</a>.<a class="footnote-ref" id="fnref:16" href="#fn:16">16</a> Several synthetic procedures are established making it accessible on scales useful for synthesis to derive bicyclo[1.1.1]pentane which are used a bioisosteres for para-substituted arene systems.<a class="footnote-ref" id="fnref:17" href="#fn:17">17</a></li>
<li>[2.1.1]Propellane, C6H8, CAS number <a href="https://commonchemistry.cas.org/detail?cas_rn=36120-91-9&title=">36120-91-9</a> (K. Wiberg, F. Walker, W. Pratt, and J. Michl). This compound was detected by <a href="/facts/Infrared_spectroscopy/u1Hzx617">infrared spectroscopy</a> at 30 <a href="/facts/Kelvin/E3trzC4C">K</a> but has not been isolated as a stable molecule at room temperature (as of 2003). It is believed to polymerize above 50 K. The bonds of the shared carbons have an inverted tetrahedral geometry; the compound's strain energy was estimated as 106 kcal/mol.<a class="footnote-ref" id="fnref:18" href="#fn:18">18</a></li>
<li>[2.2.1]Propellane, C7H10, CAS number <a href="https://commonchemistry.cas.org/detail?cas_rn=36120-90-8&title=">36120-90-8</a> (F. Walker, K. Wiberg, and J. Michl, 1982). Obtained gas-phase dehalogenation with <a href="/facts/Alkali_metal/IkWbCLk2">alkali metal</a> atoms. Stable only in frozen gas matrix below 50 K; oligomerizes or polymerizes at higher temperatures. The strain energy released by breaking the axial bond was estimated as 75 kcal/mol.<a class="footnote-ref" id="fnref:19" href="#fn:19">19</a></li>
<li>[3.1.1]Propellane, C7H10, CAS number <a href="https://commonchemistry.cas.org/detail?cas_rn=65513-21-5&title=">65513-21-5</a> (<a href="/facts/Paul_G._Gassman/7lt56y8j">Gassman</a>, 1980;<a class="footnote-ref" id="fnref:20" href="#fn:20">20</a> Szeimies, 1992;<a class="footnote-ref" id="fnref:21" href="#fn:21">21</a> <a href="/facts/Edward_Anderson_(chemist)/6BdyrREj">Anderson</a>, 2022<a class="footnote-ref" id="fnref:22" href="#fn:22">22</a>). Several synthetic procedures are established making it accessible on scales useful for synthesis to derive bicyclo[3.1.1]heptanes which are proposed as isosteres for meta-substituted arene systems.<a class="footnote-ref" id="fnref:23" href="#fn:23">23</a></li>
<li>[3.2.1]Propellane or tricyclo[3.2.1.01,5]octane, C8H12, CAS number <a href="https://commonchemistry.cas.org/detail?cas_rn=19074-25-0&title=">19074-25-0</a> (K. Wiberg and G. Burgmaier, 1969). Isolable. Has inverted tetrahedral geometry at the shared carbons. Estimated strain energy of 60 kcal/mol. Remarkably resistant to <a href="/facts/Thermal_decomposition/Qqx9RqkW">thermolysis</a>; polymerizes in <a href="/facts/Diphenyl_ether/SRlyMjHG">diphenyl ether</a> solution with halflife of about 20 hours at 195 °C. It reacts spontaneously with oxygen at room temperature to give a copolymer with –O–O– bridges.<a class="footnote-ref" id="fnref:24" href="#fn:24">24</a><a class="footnote-ref" id="fnref:25" href="#fn:25">25</a><a class="footnote-ref" id="fnref:26" href="#fn:26">26</a><a class="footnote-ref" id="fnref:27" href="#fn:27">27</a><a class="footnote-ref" id="fnref:28" href="#fn:28">28</a></li>
<li>[4.1.1]Propellane, C8H12, CAS number <a href="https://commonchemistry.cas.org/detail?cas_rn=51273-56-4&title=">51273-56-4</a> (D. Hamon, V. Trennery, 1981) Isolable.<a class="footnote-ref" id="fnref:29" href="#fn:29">29</a><a class="footnote-ref" id="fnref:30" href="#fn:30">30</a><a class="footnote-ref" id="fnref:31" href="#fn:31">31</a><a class="footnote-ref" id="fnref:32" href="#fn:32">32</a></li>
<li><a href="/facts/2.2.2-Propellane/B33lT9da">[2.2.2]Propellane</a> or tricyclo[2.2.2.01,4]octane, C8H12, CAS number <a href="https://commonchemistry.cas.org/detail?cas_rn=36120-88-4&title=">36120-88-4</a> (<a href="/facts/Philip_Eaton/N0f9c9am">P. Eaton</a> and G. Temme, 1973).<a class="footnote-ref" id="fnref:33" href="#fn:33">33</a><a class="footnote-ref" id="fnref:34" href="#fn:34">34</a> This propellane is unstable, too, due to the three <a href="/facts/Cyclobutane/hzsbc9ML">cyclobutane</a>-like rings and the highly distorted bond angles (three of them nearly 90°, the other three nearly 120°) at the axial carbons. Its <a href="/facts/Strain_energy/xQhccQG5">strain energy</a> is estimated to be 93 kcal/mol (390 kJ/mol).</li>
<li>[3.3.3]Propellane, C11H18, CAS number <a href="https://commonchemistry.cas.org/detail?cas_rn=51027-89-5&title=">51027-89-5</a> . It is a stable solid that melts at 130 °C.<a class="footnote-ref" id="fnref:35" href="#fn:35">35</a> It was synthesized in 1978 by Robert W. Weber and James M. Cook who developed a general synthetic route for all [n, 3, 3]propellanes, with n ≥ 3:<a class="footnote-ref" id="fnref:36" href="#fn:36">36</a></li></ul>

<ul><li>[4.3.3]Propellane, C12H20, CAS number <a href="https://commonchemistry.cas.org/detail?cas_rn=7161-28-6&title=">7161-28-6</a> (R. Weber and J. Cook, 1978). A stable solid that melts at 100–101 °C.<a class="footnote-ref" id="fnref:37" href="#fn:37">37</a></li>
<li>[6.3.3]Propellane, C14H24, CAS number <a href="https://commonchemistry.cas.org/detail?cas_rn=67140-86-7&title=">67140-86-7</a> (R. Weber and J. Cook, 1978). An oily liquid that boils at 275–277 °C.<a class="footnote-ref" id="fnref:38" href="#fn:38">38</a></li>
<li>[10.3.3]Propellane, C18H32, CAS number <a href="https://commonchemistry.cas.org/detail?cas_rn=58602-52-1&title=">58602-52-1</a> (S. Yang and J. Cook, 1976). A stable solid that sublimes at 33–34 °C.<a class="footnote-ref" id="fnref:39" href="#fn:39">39</a></li></ul>
<h3>Propellane derivatives</h3>
<ul><li><a href="/facts/1%2c3-Dehydroadamantane/l3gvNFE5">1,3-Dehydroadamantane</a>, C10H14 (Pincock and Torupka, 1969).<a class="footnote-ref" id="fnref:40" href="#fn:40">40</a> This compound is formally derived from <a href="/facts/Adamantane/tlvgCxYf">adamantane</a> by removing two hydrogens and adding an internal bond. It can be viewed as [3.3.1]propellane (whose axis would be the new bond), with an extra <a href="/facts/Methylene_bridge/t3lvUJuT">methylene bridge</a> between its two larger "propeller blades". It is unstable and reactive and can be polymerized.</li>
<li>2,4-Methano-2,4-dehydroadamantane: C11H14 (Majerski, 1980)<a class="footnote-ref" id="fnref:41" href="#fn:41">41</a> It can be interpreted as an adamantyl-caged [3.1.1]propellane derivative. A general reactivity profile was investigated showing similarities to the omniphilic behaviour of [1.1.1]propellane.</li></ul>
<h3>Propellane natural products</h3>
<ul><li>Dichrocephone B, a sesquiterpenoid with a [3.3.3]propellane core was isolated in 2008 from Dichrocephala benthamii.<a class="footnote-ref" id="fnref:42" href="#fn:42">42</a> It was first synthesized in 2018<a class="footnote-ref" id="fnref:43" href="#fn:43">43</a> using a general strategy<a class="footnote-ref" id="fnref:44" href="#fn:44">44</a> for the synthesis of carbocyclic propellanes from 1,3-cycloalkanediones.</li></ul>
<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/Cycloalkane/8dQAoD1N">Cycloalkane</a></li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1">Dilmaç, A. M.; Spuling, E.; de Meijere, A.; Bräse, S. (2017). "Propellanes—From a Chemical Curiosity to "Explosive" Materials and Natural Products". Angew. Chem. Int. Ed. 56 (21): 5684–5718. doi:10.1002/anie.201603951. PMID 27905166. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></li>
<li id="fn:2">Osmont; et al. (2008). "Physicochemical Properties and Thermochemistry of Propellanes". Energy and Fuels. 22 (4): 2241–2257. doi:10.1021/ef8000423. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></li>
<li id="fn:3">Dilmaç, A. M.; Spuling, E.; de Meijere, A.; Bräse, S. (2017). "Propellanes—From a Chemical Curiosity to "Explosive" Materials and Natural Products". Angew. Chem. Int. Ed. 56 (21): 5684–5718. doi:10.1002/anie.201603951. PMID 27905166. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></li>
<li id="fn:4">Altman, J.; Babad, E.; Itzchaki, J.; Ginsburg, D. (1966). "Propellanes—I". Tetrahedron. 22: 279–304. doi:10.1016/S0040-4020(01)82189-X. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></li>
<li id="fn:5">Wiberg, Kenneth B. (1986). "The Concept of Strain in Organic Chemistry". Angew. Chem. Int. Ed. Engl. 25 (4): 312–322. doi:10.1002/anie.198603121. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></li>
<li id="fn:6">Michl, Josef; Radziszewski, George J.; Downing, John W.; Wiberg, Kenneth B.; Walker, Frederick H.; Miller, Robert D.; Kovacic, Peter; Jawdosiuk, Mikolaj; Bonačić-Koutecký, Vlasta (1983). "Highly strained single and double bonds". Pure Appl. Chem. 55 (2): 315–321. doi:10.1351/pac198855020315. <a href="https://doi.org/10.1351%2Fpac198855020315" target="_blank">https://doi.org/10.1351%2Fpac198855020315</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></li>
<li id="fn:7">Shaik, Sason; Danovich, David; Wu, Wei; Hiberty, Philippe C. (2009). "Charge-shift bonding and its manifestations in chemistry". Nature Chemistry. 1 (6): 443–449. doi:10.1038/nchem.327. PMID 21378912. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></li>
<li id="fn:8">Sterling, Alistair J.; Dürr, Alexander B.; Smith, Russel C.; Anderson, Edward A.; Duarte, Fernanda (2020). "Rationalizing the diverse reactivity of [1.1.1]propellane through σ–π-delocalization". Chem. Sci. 11 (19): 4895–4903. doi:10.1039/D0SC01386B. PMC 8159217. PMID 34122945. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8159217" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8159217</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></li>
<li id="fn:9">Wiberg, Kenneth B.; Waddell, Sherman T. (1990). "Reactions of [1.1.1]propellane". J. Am. Chem. Soc. 112 (6): 2194–2216. doi:10.1021/ja00162a022. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></li>
<li id="fn:10">Fuchs, Josef; Szeimies, Günter (1992). "Synthese von [n.1.1]Propellanen (n = 2, 3, 4)". Chem. Ber. 125 (11): 2517–2522. doi:10.1002/cber.19921251126. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></li>
<li id="fn:11">Frank, Nils; Nugent, Jeremy; Shire, Bethany R.; Pickford, Helena D.; Rabe, Patrick; Sterling, Alistair J.; Zarganes-Tzitzikas, Tryfon; Grimes, Thomas; Thompson, Amber L.; Smith, Russell C.; Schofield, Christopher J.; Brennan, Paul E.; Duarte, Fernanda; Anderson, Edward A. (2022). "Synthesis of meta-substituted arene bioisosteres from [3.1.1]propellane". Nature. 611 (7937): 721–726. doi:10.1038/s41586-022-05290-z. PMID 36108675. S2CID 252310498. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></li>
<li id="fn:12">Kaszynski, Piotr; Michl, Josef (1988). "[n]Staffanes: a molecular-size "Tinkertoy" construction set for nanotechnology. Preparation of end-functionalized telomers and a polymer of [1.1.1]propellane". J. Am. Chem. Soc. 110 (15): 5225–5226. doi:10.1021/ja00223a070. <a href="/wiki/J._Am._Chem._Soc." target="_blank">/wiki/J._Am._Chem._Soc.</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></li>
<li id="fn:13">Wiberg, Kenneth B.; Burgmaier, George J. (1972). "Tricyclo[3.2.1.01,5]octane. A 3,2,1-Propellane". J. Am. Chem. Soc. 94 (21): 7396–7401. doi:10.1021/ja00776a022. <a href="/wiki/Journal_of_the_American_Chemical_Society" target="_blank">/wiki/Journal_of_the_American_Chemical_Society</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></li>
<li id="fn:14">Weber, Robert W.; Cook, James M. (1978). "General method for the synthesis of [n.3.3]propellanes, n ≥ 3". Can. J. Chem. 56 (2): 189–192. doi:10.1139/v78-030. <a href="https://doi.org/10.1139%2Fv78-030" target="_blank">https://doi.org/10.1139%2Fv78-030</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></li>
<li id="fn:15">Wiberg, Kenneth B.; Walker, Frederick H. (1982). "[1.1.1]Propellane". J. Am. Chem. Soc. 104 (19): 5239–5240. doi:10.1021/ja00383a046. <a href="/wiki/J._Am._Chem._Soc." target="_blank">/wiki/J._Am._Chem._Soc.</a> <a href="#fnref:15" class="footnote-back-ref">↩</a></li>
<li id="fn:16">Kaszynski, Piotr; Michl, Josef (1988). "[n]Staffanes: a molecular-size "Tinkertoy" construction set for nanotechnology. Preparation of end-functionalized telomers and a polymer of [1.1.1]propellane". J. Am. Chem. Soc. 110 (15): 5225–5226. doi:10.1021/ja00223a070. <a href="/wiki/J._Am._Chem._Soc." target="_blank">/wiki/J._Am._Chem._Soc.</a> <a href="#fnref:16" class="footnote-back-ref">↩</a></li>
<li id="fn:17">Stepan, Antonia F.; et al. (2012). "Application of the Bicyclo[1.1.1]pentane Motif as a Nonclassical Phenyl Ring Bioisostere in the Design of a Potent and Orally Active γ-Secretase Inhibitor". J. Med. Chem. 55 (7): 3414–3424. doi:10.1021/jm300094u. PMID 22420884. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:17" class="footnote-back-ref">↩</a></li>
<li id="fn:18">Jarosch, Oliver; Szeimies, Günter (2003). "Thermal Behavior of [2.1.1]Propellane: A DFT/Ab Initio Study". J. Org. Chem. 68 (10): 3797–3801. doi:10.1021/jo020741d. PMID 12737556. <a href="/wiki/J._Org._Chem." target="_blank">/wiki/J._Org._Chem.</a> <a href="#fnref:18" class="footnote-back-ref">↩</a></li>
<li id="fn:19">Walker, Frederick H.; Wiberg, Kenneth B.; Michl, Josef (1982). "[2.2.1]Propellane". J. Am. Chem. Soc. 104 (7): 2056. doi:10.1021/ja00371a059. <a href="/wiki/Journal_of_the_American_Chemical_Society" target="_blank">/wiki/Journal_of_the_American_Chemical_Society</a> <a href="#fnref:19" class="footnote-back-ref">↩</a></li>
<li id="fn:20">Gassman, P. G.; Proehl, G. S. (1980). "[3.1.1]Propellane". J. Am. Chem. Soc. 102 (22): 6862. doi:10.1021/ja00542a040. <a href="/wiki/Journal_of_the_American_Chemical_Society" target="_blank">/wiki/Journal_of_the_American_Chemical_Society</a> <a href="#fnref:20" class="footnote-back-ref">↩</a></li>
<li id="fn:21">Fuchs, Josef; Szeimies, Günter (1992). "Synthese von [n.1.1]Propellanen (n = 2, 3, 4)". Chem. Ber. 125 (11): 2517–2522. doi:10.1002/cber.19921251126. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:21" class="footnote-back-ref">↩</a></li>
<li id="fn:22">Frank, Nils; Nugent, Jeremy; Shire, Bethany R.; Pickford, Helena D.; Rabe, Patrick; Sterling, Alistair J.; Zarganes-Tzitzikas, Tryfon; Grimes, Thomas; Thompson, Amber L.; Smith, Russell C.; Schofield, Christopher J.; Brennan, Paul E.; Duarte, Fernanda; Anderson, Edward A. (2022). "Synthesis of meta-substituted arene bioisosteres from [3.1.1]propellane". Nature. 611 (7937): 721–726. doi:10.1038/s41586-022-05290-z. PMID 36108675. S2CID 252310498. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:22" class="footnote-back-ref">↩</a></li>
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</ol>

Propellane open-in-new

Propellane