Titanium(IV) Chloride-2,2,6,6-Tetramethylpiperidine


[7550-45-0]  · Cl4Ti  · Titanium(IV) Chloride-2,2,6,6-Tetramethylpiperidine  · (MW 189.68) (TMP)

[768-66-1]  · C9H19N  · Titanium(IV) Chloride-2,2,6,6-Tetramethylpiperidine  · (MW 141.29)

(oxophilic Lewis acid for the intramolecular cyclization of unsaturated (Z)-allylic alcohols1)

Physical Data: see Titanium(IV) Chloride and 2,2,6,6-Tetramethylpiperidine.

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

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

Preparative Methods: TMP (1.5 equiv) is added to a solution of TiCl4 (1.5 equiv) in dichloromethane at 0 °C. It is assumed that a complex, analogous to the TiCl4-N-methylaniline complex,1,2 is formed. The mixture is then cooled to -23 °C and the (Z)-allylic alcohol added.

Handling, Storage, and Precautions: TiCl4 is corrosive and moisture-sensitive. TMP is a flammable liquid which should be stored in colored glass. The reagent will be moisture sensitive so the reactions are best performed under a dry inert atmosphere. Solvents should be dried before use.

Cyclization of Unsaturated (Z)-Allylic Alcohols.

Nerol has been cyclized using TiCl4-TMP to give the chloroisopropylcyclohexene shown (eq 1).1 Use of TiCl4 alone gave a complex mixture. The use of N-methylaniline in place of TMP gave (1) in 67%; this latter reagent has been much more widely used. By analogy, (E)-allylic alcohols could be expected to give the allylic halide, as could (Z)-allylic alcohols lacking further suitably disposed alkenic bonds.

Related Reagents.

Titanium(IV) Chloride.

1. Saito, T.; Itoh, A.; Oshima, K.; Nozaki, H. TL 1979, 3519.
2. See also Burger, V. H.; Nesse, H. J. Z. Anorg. Allg. Chem. 1969, 365, 243.

Ian C. Richards

AgrEvo, Saffron Walden, UK

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