Treatment of a titanatrane complex with trimethylsilyl chloride and magnesium powder in tetrahydrofuran generated a low‐valent titanium species. This species catalyzed the radical ring opening of epoxides and oxetanes to produce the corresponding less substituted alcohols. The reagent also catalyzed the deallylation and depropargylation of allylic and propargylic ethers, respectively, to provide the parent alcohols.magnified image

A low-valent titanium species derived in situ from Ti(O-i-Pr)(4), Me(3)SiCl and Mg powder in tetrahydrofuran reacted with epoxides to selectively provide less hindered alcohols via a homolytic ring-opening of epoxides, in which the intermediate β-titanoxy radical intramolecularly abstracted a hydrogen atom from an alkoxy moiety in the titanium complexes.

Abstraction in β-Titanoxy Radical Intermediates. -A new method for the synthesis of less hindered alcohols via homolytic ring opening of epoxides is described. Mechanistic studies indicate an intramolecular hydrogen abstraction from the Ti-isopropoxy moiety. The addition of an external hydrogen atom source is therefore not required and furthermore allows for a stereoselective conversion of bicyclic epoxides (IX) to give the corresponding anti-configured products (X). Functionalities such as acetal, alkene and silyl ether groups are tolerated under the reaction conditions. -(KAWAJI, T.; SHOHJI, N.; MIYASHITA, K.; OKAMOTO*, S.; Chem. Commun. (Cambridge) 47 (2011) 27, 7857-7859, http://dx.

The first examples of the C-O bond cleavage of various oxetanes at the 2-position using low valent titanium alkoxides, generated in situ from the titanatrane complex, Mg, and TmsCl, are presented. Addition of 1,4-cyclohexadiene is beneficial. The catalytic system is also effective in the deallylation and depropargylation of ethers. -(TAKEKOSHI, N.; MIYASHITA, K.; SHOJI, N.; OKAMOTO*, S.; Adv. Synth. Catal. 355 (2013) 11-12, 2151-2157, http://dx.