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    A New Rotane Family:  Synthesis, Structure, Conformation, and Dynamics of [3.4]-, [4.4]-, [5.4]-, and [6.4]Rotane<sup>1</sup> by Lutz Fitjer (2466634)

    Published 1998
    “…All syntheses are based on bicyclobutylidene (<b>9</b>):  [2+1] cycloaddition of cyclobutylidene yields [3.4]rotane (<b>5</b>) (<b>9</b>−<b>5</b>), [2+2] cycloaddition of trimethyleneketene followed by spiroalkylation of the resulting trispiroketone <b>10</b> yields [4.4]rotane (<b>6</b>) (<b>9</b>−<b>10</b>−<b>13</b>−<b>14</b>−<b>6</b>), homologization of <b>10</b> via β-hydroxy selenides gives access to tetraspiroketone <b>11</b> and pentaspiroketone <b>12</b> (<b>10</b>−<b>15</b>−<b>11</b>−<b>16</b>−<b>12</b>), and further elaboration directed toward a cyclopropylcarbene−cyclobutene rearrangement yields [5.4]rotane (<b>7</b>) and [6.4]rotane (<b>8</b>) [<b>11</b>(<b>12</b>)−<b>18</b>(<b>24</b>)−<b>19</b>(<b>25</b>)−<b>20</b>(<b>26</b>)−<b>21</b>(<b>27</b>)−<b>22</b>(<b>28</b>)−<b>23</b>(<b>29</b>)−<b>7</b>(<b>8</b>)]. …”
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