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Base Mediated Displacement

Mechanism + Description

Intramolecular ring closure of alcohol α to a suitable leaving group.

General comments

Generally scalable epoxide formation by SN2 displacement of a leaving group adjacent to a hydroxyl function. Widely applicable for a range of substrates. May not be suitable where other base sensitive groups are present. For the closure of halohydrins, the reaction is often combined with the oxidation of the alkene with halogen reagents and acids/PTC’s. Epoxidations with bleach (NaOCl) normally occur via formation of the chlorohydrin and in situ closure to the epoxide.

Key references

Adv. Synth. Catal. 2003, 345, No. 3, 389 Convenient Method for Epoxidation of Olefins without Metal Catalysts
Org. Synth. Coll. Vol. 8, 1993, 434-442 (1988, 66, 160-168) example of base epoxidation.
J. Am. Chem. Soc., 2004, 126, 6844-6845  chiral catalysts for the highly enantioselective epoxidation of α,β-unsaturated ketones

Relevant scale up example

Gram scale

Org. Process Res. Dev. 2009, 13, 1111–1121

82 kg scale

Org. Process Res. Dev. 2002, 6, 721- 728s

3 kg scale

Org. Process Res. Dev. 2002, 6, 721- 728

1 kg scale

Org. Process Res. Dev. 2012, 16 1558–1565