Titanium (low valent)
A one-pot, selective cross pinacol-type coupling between two structurally similar aromatic aldehydes in the presence of low-valent titanium gave unsymmetrical pinacols in good yields and diastereoselectivities. This synthetic methodology, which is based on the affinity of the substituents to the surface of titanium, significantly extends the scope of the cross pinacol-type couplings.
X.-F. Duan, J.-X. Feng, G.-F. Zi, Z.-B. Zhang, Synthesis, 2009, 277-282.
Low-valent Cp2TiCl selectively reduces selected α,β-epoxy ketones to the corresponding aldol products under mild conditions. A chiral epoxide was converted without any loss of optical purity. The addition of collidine hydrochloride enables a system catalytic in titanocene.
C. Hardouin, F. Chevallier, B. Rousseau, E. Doris, J. Org. Chem., 2001, 66, 1046-1048.
A low-valent titanium generated in situ from Ti(O-i-Pr)4, Me3SiCl, and Mg powder in THF reacted with a broad range of sulfonamides in a reductive bond cleaving pathway to provide the corresponding amines, hydrocarbons and thiols. The reagent could also cleave sulfonates to the corresponding alcohols.
N. Shohji, T. Kawaji, S. Okamoto, Org. Lett., 2011, 13, 2626-2629.
A nickel-catalyzed cross-electrophile coupling reaction between benzyl alcohols and aryl halides is mediated by a low-valent titanium reagent generated from TiCl4(2,6-lutidine) and manganese powder. The reaction afforded the cross-coupled product in high yield.
T. Suga, Y. Ukaji, Org. Lett., 2018, 20, 7846-7850.