Comments on: Reagent Friday: Lithium Di-isopropyl Amide (LDA) https://www.masterorganicchemistry.com/2011/08/05/reagent-friday-lithium-di-isopropyl-amide-lda/ Thu, 12 Sep 2024 17:21:30 +0000 hourly 1 https://wordpress.org/?v=6.6.2 By: James Ashenhurst https://www.masterorganicchemistry.com/2011/08/05/reagent-friday-lithium-di-isopropyl-amide-lda/#comment-706568 Thu, 12 Sep 2024 17:21:30 +0000 https://www.masterorganicchemistry.com/?p=1891#comment-706568 In reply to Moses Alege.

LDA will not attach, but it may be strong enough to form an aryne. For example one could deprotonate C-H and elimination of the best leaving group (Cl) would give an aryne, which could then undergo attack by a nucleophile. When the nucleophile does attack, it will likely do so such that the negative charge is placed closer to the electron withdrawing fluoro groups.
See this artice on arynes – possibly helpful. https://www.masterorganicchemistry.com/2018/09/17/nucleophilic-aromatic-substitution-2-benzyne/

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By: Moses Alege https://www.masterorganicchemistry.com/2011/08/05/reagent-friday-lithium-di-isopropyl-amide-lda/#comment-706466 Thu, 12 Sep 2024 03:34:53 +0000 https://www.masterorganicchemistry.com/?p=1891#comment-706466 What will the attaching position of LDA for 1-chloro-3,4-difluorobenzene?

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By: James Ashenhurst https://www.masterorganicchemistry.com/2011/08/05/reagent-friday-lithium-di-isopropyl-amide-lda/#comment-652392 Sat, 15 Apr 2023 03:33:19 +0000 https://www.masterorganicchemistry.com/?p=1891#comment-652392 In reply to Lena.

Sometimes on benzene rings with a good leaving group it will deprotonate C-H adjacent to the carbon with a good leaving group, resulting in a new pi bond. These species are called “arynes”. https://www.masterorganicchemistry.com/2018/09/17/nucleophilic-aromatic-substitution-2-benzyne/

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By: Lena https://www.masterorganicchemistry.com/2011/08/05/reagent-friday-lithium-di-isopropyl-amide-lda/#comment-652378 Fri, 14 Apr 2023 22:45:47 +0000 https://www.masterorganicchemistry.com/?p=1891#comment-652378 How does LDA react with a benzene ring?

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By: James Ashenhurst https://www.masterorganicchemistry.com/2011/08/05/reagent-friday-lithium-di-isopropyl-amide-lda/#comment-586210 Fri, 16 Oct 2020 17:58:54 +0000 https://www.masterorganicchemistry.com/?p=1891#comment-586210 In reply to Christina.

Alkylation of enolates with alkyl halides is an SN2 reaction, and SN2 reactions will only occur at sp3-hybridized carbons. In the reaction you describe, only the 1-carbon is sp3-hybridized, and thus the enolate will perform substitution at C-1. The C-Br bond at C2 will be unaffected. Sorry for taking so long to get back to you.

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By: James Ashenhurst https://www.masterorganicchemistry.com/2011/08/05/reagent-friday-lithium-di-isopropyl-amide-lda/#comment-573050 Sat, 14 Dec 2019 04:49:20 +0000 https://www.masterorganicchemistry.com/?p=1891#comment-573050 In reply to Rava.

No, but there will be a change in selectivity. It won’t be as selective for the less substituted enolate at a higher temperature.

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By: James Ashenhurst https://www.masterorganicchemistry.com/2011/08/05/reagent-friday-lithium-di-isopropyl-amide-lda/#comment-561939 Tue, 27 Aug 2019 21:08:13 +0000 https://www.masterorganicchemistry.com/?p=1891#comment-561939 In reply to Collin Rebello.

Confusingly, the name for the amide linkage you speak of, and the name of the conjugate base of an amine are both “amide”. Some chemists pronounce the two differently but that doesn’t really translate to the written word. It’s helpful to use the term “metal amide” when referring to the conjugate base – this differentiates it from the (neutral) functional group.

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By: Collin Rebello https://www.masterorganicchemistry.com/2011/08/05/reagent-friday-lithium-di-isopropyl-amide-lda/#comment-561913 Tue, 27 Aug 2019 15:16:11 +0000 https://www.masterorganicchemistry.com/?p=1891#comment-561913 Why does it have amide in the end, even though amide linkage is not seen in LDA ?

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By: James Ashenhurst https://www.masterorganicchemistry.com/2011/08/05/reagent-friday-lithium-di-isopropyl-amide-lda/#comment-560675 Thu, 15 Aug 2019 17:32:50 +0000 https://www.masterorganicchemistry.com/?p=1891#comment-560675 In reply to Raza.

LDA formation would essentially be instantaneous at –20 °C. In fact it’s not uncommon to make the LDA at sub-zero temperature and then cool it to -78 prior to using it for enolate formation.

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By: James Ashenhurst https://www.masterorganicchemistry.com/2011/08/05/reagent-friday-lithium-di-isopropyl-amide-lda/#comment-557855 Tue, 09 Jul 2019 18:55:36 +0000 https://www.masterorganicchemistry.com/?p=1891#comment-557855 In reply to Faizah.

The pKa of the CH3 adjacent to a triple bond is at least 40, so without significant heating, no.

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