Titanium(IV) Chloride-Diazabicyclo[5.4.0]undec-7-ene


[7550-45-0]  · Cl4Ti  · Titanium(IV) Chloride-Diazabicyclo[5.4.0]undec-7-ene  · (MW 189.68) (DBU)

[6674-22-2]  · C9H16N2  · Titanium(IV) Chloride-Diazabicyclo[5.4.0]undec-7-ene  · (MW 152.27)

(combination of reagents which allows the opening of epoxides to give chlorohydrins in the presence of acid labile groups1)

Physical Data: see Titanium(IV) Chloride and 1,8-Diazabicyclo[5.4.0]undec-7-ene.

Solubility: TiCl4: sol aromatic hydrocarbons, ether, THF, dioxane, chlorohydrocarbons. DBU: sol ethers, chlorohydrocarbons, aromatic solvents.

Form Supplied in: TiCl4: colorless liquid, or as a crystalline complex with THF. DBU: colorless liquid.

Preparative Methods: DBU (2 equiv) is added to a solution of the epoxide in dichloromethane. The mixture is cooled to -78 °C. TiCl4 (1 equiv) is then added and the mixture allowed to warm to rt.

Handling, Storage, and Precautions: TiCl4 is corrosive and moisture sensitive. DBU is a flammable liquid. The combination reagent is moisture sensitive and reactions are best performed under a dry inert atmosphere. Solvents should be dried before use.

Preparation of Chlorohydrins.

Epoxides are treated with the reagent to give chlorohydrins.1 Mono- and disubstituted epoxides are converted in excellent yields (eq 1). Trisubstituted epoxides give moderate yields. The regiochemical outcome is such that the chlorine is added to the more stabilized carbocation center and the stereochemistry is that of a trans opening of the epoxide. The chlorohydrin (2) obtained from (-)-dihydrogeraniol epoxide (1) could be converted back to the epoxide without loss of optical activity (eq 2).1 The presence of DBU is essential for the survival of acid-sensitive groups such as acetals. 4-Dimethylaminopyridine has been used as an alternative to DBU but the yields are lower.

Related Reagents.

Dichlorotitanium Diisopropoxide; Tin(II) Chloride; Titanium(IV) Chloride.

1. Spawn, C. L.; Drtina, G. J.; Wiemer, D. F. S 1986, 315.

Ian C. Richards

AgrEvo, Saffron Walden, UK

Copyright 1995-2000 by John Wiley & Sons, Ltd. All rights reserved.