Talk:Claisen rearrangement

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Wiki should be able to name organic reactions and not wait for others, I have never heard of a named reaction named after a female [1] could be a first!.

Wiki Education Foundation-supported course assignment

This article is or was the subject of a Wiki Education Foundation-supported course assignment. Further details are available on the course page. Student editor(s): Kchemyoung.

Above undated message substituted from Template:Dashboard.wikiedu.org assignment by PrimeBOT (talk) 17:46, 16 January 2022 (UTC) == There are people who are taken to calling nucleophilic interception of the Staudinger ligation product the "Bertozzi-Staudinger reaction", but it's not synthetically useful, and it's not particularly novel. Also, the transition-metal catalyzed version of the Mapp Reaction was independently and concurrently reported in the literature by another group, but the Mapp group did a more thorough characterization of both reactions very shortly afterward.[reply]

In the image http://en.wikipedia.org/wiki/Image:Ireland-Claisen_Rearrangement_Scheme.png BuLi is not the correct base to have over the reaction arrow. The problem is that BuLi will reaction with the ester at the carbonyl (as a nucleophile rather than a base) to produce a tertiary alcohol. LDA is a better choice of base. I can re-do the figure, but at the moment I'll leave this edit for the author of the original figure. BTW: Nice page!

for the chromium oxidation step, it is easier to picture the arrows as being drawn from the Cr-alkoxide attacking the activated alcohol in an sn2' type attack. also, this is the Dauben Oxidation. etheiste —Preceding unsigned comment added by Etheiste (talk • contribs) 19:10, 7 July 2009 (UTC)[reply]

Incorrectly drawn mechanisms!

The arrows for critical steps of the mechanisms for the Eschenmoser-Claisen, the Ireland-Claisen, Johnson-Claisen and the Chromium oxidation are incorrectly drawn and should reflect the proper flow of electrons during the rearrangement process. It would also be of better service to cite a peer reviewed journal article such as Chemical Review or any of the other numerous reviews or a commonly used advanced text book instead of the rare specialty books. It may also make more sense to move the oxidation chemistry and the allylic rearrangements to individual pages and include links. DrRerNatDHW (talk) 15:27, 6 March 2011 (UTC)[reply]

Easy enough to fix the diagrams, if you could please clarify which specific pieces of which specific files are wrong? For example, the key pericyclic step of the Johnson-Claisen mechanism, the mechanism for the "heat" of File:Johnson Claisen Mechanism.png, looks fine in that reaction sequence. DMacks (talk) 19:13, 12 March 2011 (UTC)[reply]

I disagree with the way the arrows are drawn in the rearrangement step of the depicted Claisen rearrangements. In a sigmatropic rearrangement the bonds are broken and made at the same time, the transition state is cyclic and characterized by a negative entropy of activation (-ΔS‡), a negative volume of activation (-ΔV‡), and first order kinetics.(1, 2) Although the bonds are roughly made and broken at the same time the mechanism is clearly asynchronous and electron donating and withdrawing groups affect the rate of reaction. As such, the mechanism can be drawn in several ways with varying degrees of appropriateness. Computational and physical studies have indicated that the transition state can go by either a chair or boat conformation and both pathways can be operating at the same time.(3) However, pushing arrows is especially appropriate when polar groups are involved and can give a better “feel” to the electron flow. There is logic to pushing arrows that should be followed when attempting to convey mechanisms to accurately reflect the observations. Drawn below is the corrected arrow pushing mechanism. Here the electron rich vinyl diether group which is typically very nucleophilic will donate electrons from the π bond between C2 and C3 to a new σ bond between C3 and C4, this is drawn correctly by starting from the middle of the double bond with the arrow pointing to the C4 carbon (to signify the electron movement to that group). To do this, the π bond between C4 and C5 is shifted to a new π bond between C5 and C6, correctly drawn by starting from the middle of the C=C bond between C4 and C5 to the middle of the new bond forming between C5 and C6. The C-O σ bond between C6 and O1 breaks and the electrons flow to the more electronegative atom or into the most electron withdrawing group in the new molecule, namely the resulting carbonyl of the ester, this is drawn with the arrow leaving from the middle of the C-O σ bond (signifying that bond is breaking) to the middle of the newly forming carbonyl group (signifying that bond is being made). The last problem I have with the mechanisms as drawn are the double arrows, which in a simplified overview are correct in that the Claisen can be a reversible process, in effect the reaction toward the ester product is so downhill it is for all normal purposes irreversible (with a few notable exceptions). References 1. Ziegler, F. E., The thermal, aliphatic Claisen rearrangement. Chemical Reviews 1988, 88, (8), 1423-1452. 2. Gajewski, J. J., The Claisen Rearrangement. Response to Solvents and Substituents: The Case for Both Hydrophobic and Hydrogen Bond Acceleration in Water and for a Variable Transition State. Accounts of Chemical Research 1997, 30, (5), 219-225. 3. Martín Castro, A. M., Claisen Rearrangement over the Past Nine Decades. Chemical Reviews 2004, 104, (6), 2939-3002. — Preceding unsigned comment added by DrRerNatDHW (talk • contribs) 16:45, 28 March 2011 (UTC)[reply]