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I am helping a friend with some upper-level mechanism problems. We came across this one. This is my proposal. Do you agree/disagree? Thank you for any input. enter image description here

Source question: enter image description here

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    $\begingroup$ In your mechanism, you have an anion next to a nitrile: that is good, but you should not draw it as a chair anymore, that carbon with a negative charge should be sp2, precisely because of the resonance stabilisation. $\endgroup$
    – orthocresol
    May 25 at 16:43
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    $\begingroup$ You shows in your second structure, Grignard attacking the $\alpha$ carbon to carbonyl (not carbonyl anymore though), yet you shows methyl on the $\beta$ carbon to carbonyl with negative charge making $\beta$ carbon pentavalent (with negative charge). This should be fixed ASAP. $\endgroup$ May 25 at 17:44
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    $\begingroup$ The first two structures in the third line are not related to the starting cyanoketone. The carbonyl group is in the wrong position in the first structure. $\endgroup$
    – user55119
    May 25 at 22:09
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    $\begingroup$ The details are here: pubs.acs.org/doi/pdf/10.1021/jo052102j $\endgroup$
    – user55119
    May 25 at 22:17
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    $\begingroup$ @user55119: You are correct about the error. Also, the carbonyl group is in the wrong position not only in the first structure, but also in the second structure. Rest is okay. $\endgroup$ May 25 at 22:35
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Mechanism I developed from the paper @user55119 graciously provided. Appreciate it! Any refinements I appreciate. :)

enter image description here

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  • $\begingroup$ One suggestion. Although the relative stereochemistry is what is important, try not to switch absolute stereochemistry as you have done in line 2. For the right hand structure in line 2, draw the same chair cyclohexane but shift all substituents one carbon to the left where axial becomes equatorial and equatorial becomes axial. $\endgroup$
    – user55119
    May 27 at 15:05

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