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Facile Preparation of (2Z,4E)-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate
Published on: June 21, 2017
Selectivity control in alkylidene carbene-mediated C-H insertion and allene formation
Jun-Cheng Zheng1, Sang Young Yun, Chunrui Sun
1Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607, USA.
Electronic effects dominate regioselectivity in alkylidene carbene C-H insertion reactions, surpassing steric influences. This understanding enables precise control over carbene insertion into various C-H bonds.
Area of Science:
- Organic Chemistry
- Reaction Mechanisms
- Catalysis
Background:
- Alkylidene carbenes are reactive intermediates crucial for C-H bond functionalization.
- Controlling regioselectivity in carbene insertion reactions is essential for synthetic efficiency.
Purpose of the Study:
- To investigate the factors governing the regioselectivity of alkylidene carbene-mediated C-H insertion.
- To elucidate the interplay between electronic, conformational, steric, and stereoelectronic effects.
Main Methods:
- Exploration of C-H insertion reactions using various substrates.
- Analysis of reaction outcomes based on electronic, steric, and conformational properties of C-H bonds.
Main Results:
- Highly regio- and chemoselective carbene insertion was achieved by considering key factors.
- Electronic effects were found to be more influential than steric effects in determining selectivity.
- C-H bonds in rigid cyclic systems showed reduced reactivity compared to acyclic systems.
Conclusions:
- Understanding electronic and conformational factors allows for predictable control of carbene insertion regioselectivity.
- Competing reactions, such as allenylsilane formation, are favored under specific conditions (high concentration, deactivated C-H bonds).
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