Birch Reduction of Electron-Rich and Electron-Poor Aromatic Molecules – Examples và Mechanisms
The Birch Reduction is a process for converting benzene (and its aromatic relatives) khổng lồ 1,4-cyclohexadiene using sodium (or lithium) as a reducing agent in liquid ammonia as solvent (boiling point: –33°C) in the presence of an alcohol such as ethanol, methanol or t-butanol.
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Table of Contents
1. The Birch Reduction
When benzene is treated with metallic sodium (or lithium) in liquid ammonia as a solvent, in the presence of a proton source (e.g. Ethanol, methanol, or t-butanol) the result is the net reduction of one of the double bonds of the benzene ring khổng lồ give 1,4-cyclohexadiene.
(Advanced) References & Further Reading
This article from the In The Pipeline blog by Derek Lowe provides an accessible (no formulae), colorful, & interesting background on the Birch reduction, along with a discussion of a recent (2019) advance in the electrochemical Birch reduction (see reference 8).
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Running A Birch Reduction. From ChemTips
These handouts on the Birch Reduction from the groups of Prof. Andrew G. Myers (Harvard) & Prof. Phil S. Baran (Scripps) are particularly useful for advanced undergraduate / graduate-level students
Nobel Laureate Sir John Cornforth wrote a biographical sketch of Birch in Biographical Memoirs of Fellows of The Royal Society. This paper also notes the first chemist to use the term “Birch Reduction” was Carl Djerassi.