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Boord olefin synthesis

The Boord olefin synthesis is an organic reaction forming alkenes from ethers carrying a halogen atom 2 carbons removed from the oxygen atom (β-halo-ethers) catalyzed by a metal such as magnesium or zinc. The reaction, discovered by Cecil E. Boord in 1930 ^[1] is a classic named reaction with high yields and broad scope ^[2].

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The reaction type is an elimination reaction with magnesium forming an intermediate Grignard reagent. The alkoxy group is a poor leaving group and therefore a E1cB elimination reaction mechanism is proposed ^[2].The original publication describes the organic synthesis of the compound isoheptene in several steps with the elimination the final one:

In a 1931 publication ^[3] the scope is extended to 1,4-dienes with magnesium replaced by zinc (see also: Barbier reaction). In the first part of the reaction the allyl Grignard acts as a nucleophile in nucleophilic aliphatic substitution.

References

^ The synthesis of beta-bromo-alkyl ethers and their use in further synthesis Lloyd C. Swallen and Cecil E. Boord J. Am. Chem. Soc.; 1930; 52(2) pp 651 - 660; doi:10.1021/ja01365a033
^ ^a ^b Advanced Organic Chemistry, 4th Edition, Jerry March, 1992.
^ Nuclear syntheses in the olefin series II. 1,4-diolefins Bernard H. Shoemaker and Cecil E. Boord J. Am. Chem. Soc.; 1931; 53(4) pp 1505 - 1512; doi:10.1021/ja01355a049 10.1021/ja01355a049