[azmanam]

LAH question is still open, btw 

QUESTION: Provide a complete, arrow pushing mechanism for the following reaction.

(ps, I'm out of town next Mon, so if someone else wants to come up with a POTW, feel free to post it next week )

[Dan]

OK, this was my first thought. Not entirely confident about the 4-membered transition state in the second step, but here it is...

This would give the racemic trans substituted cyclohexane, I assume you left out the stereochem because that was going to be your next question, or is it completely scrambled?

[nj_bartel]

Seems plausible to me given you're reintroducing the aromaticity.

[azmanam]

Good guess, but no.

I left out stereochemistry because it wasn't in the original question... but I meant to add it as a bonus question.  the stereochem is not indicated in the question, but I think one could rationalize a particular orientation.  So... uh... right! that's my next question!

You're sort of on the right track, but just far enough off track to be wrong.  I get that the C-C bond cleavage restores aromaticity, but I agree with your concern over a 4-membered TS.  There's a better, less demanding way to do it.

Here's my hint:  If you go through and systematically isotopically label the molecule one at a time, the labels in the actual final product are not in the same place as the labels in your final product.

[nj_bartel]

I've got something, not sure it's more plausible than the 4 membered ring though   Give me a couple to draw

[nj_bartel]

attached.  Looking back at it, I don't think my last step is really plausible at all.

edit:  also, what do you all use to draw mechanisms?  I don't see the curvy arrow feature on chemsketch and paint does not work so well

[azmanam]

Interesting thought, but no, not quite.

I think that enolate would be preferentially nucleophilic at carbon, not oxygen, imho.  Your final structure suffers from the same labeling problem that Dan's did.  If you label the starting material, the labels would not be in the right place in your products.

as for drawing, I use ChemDraw (with TotSyn Style: http://totallysynthetic.com/blog/?page_id=287), and it looks like Dan's is also ChemDraw (but ACS style).  To do curved arrows in ChemSketch, click DRAW (next to structure in top left), then select the arrow tool (5th from top in vertical toolbar on left), then select curve (second from top in vertical toolbar on left).  You should then be able to draw a curved arrow.

[nj_bartel]

Thanks

[azmanam]

Here's that same labeling hint in pictorial form.

[orgopete]

This is my suggestion. First, the alpha-methylene loses a hydrogen (hydride?). How can I accomplish it? The phenol will stabilize or enable the donation by forming a protonated quinone methide. The complex of BF3 with the enone will accept an intramolecularly transferred hydride. Then, the newly formed enolate-BF3 complex can form a new bond to the quininone methide. That will give a six-membered ring with an alpha-acetyl group and the 13-C label will not attached to the phenyl ring.

[azmanam]

I think that sounds ok.  Someone want to draw it out?  And use that drawing to predict relative stereochemistry of product?