Lecture 35 - Acyl Insertions and alpha-Reactivity. When a nucleophilic atom bearing a good leaving group attacks a carbonyl group, an adjacent Rgroup can migrate to the new atom, inserting it into the R-acyl bond.
This mechanism can insert O, NH, or CH2 groups into the acyl bond with informative stereospecificity in the case of the Beckmann rearrangement of oximes. Although the migrating groups are formally anionic, relative migratory
aptitudes show that they give up electron density during rearrangement. Acid dissociation of protons a to a carbonyl group to form enolates, and the ease of forming enols, gives α-carbons nucleophilic reactivity under
both basic and acidic conditions. This explains H/D exchange and racemization as well as halogenation and alkylation of α-carbons.
(from oyc.yale.edu)
Lecture 35 - Acyl Insertions and alpha-Reactivity
Time
Lecture Chapters
[00:00:00]
1. Acyl Insertion of O, NH, and CH2
[00:25:26]
2. α-Acidity
[00:34:38]
3. H/D Exchange and Racemization via Enol or Enolate
[00:37:53]
4. α-Alkylation-Halogenation
[00:46:50]
5. α-Alkylation
References
Lecture 35 - Acyl Insertions and alpha-Reactivity
Instructor: Professor J. Michael McBride. Resources: Professor McBride's website resource for CHEM 125b (Spring 2011). Transcript [html]. Audio [mp3]. Download Video [mov].