Titanium-catalysed deoxygenation of benzylic alcohols and lignin model compounds

Abstract

We report a catalytic system for direct deoxygenation of benzylic alcohols by using non-precious precatalyst Cp2TiCl2 and 2 MeTHF as solvent. Mechanistic studies showed that the used silane Me(EtO)2SiH acts...

Photoinduced Low‐Valent Zirconium Catalysis for Cross‐Electrophile Coupling of Ethers

“…For instance, activated benzylic alcohols could undergo β-scission or single electron transformation (SET) to form C(sp3) radicals for further cross-coupling with alkyl (pseudoÀ ) halides in nickel catalysis, [20][21][22][23][24][25][26] homolysis of tertiary alcohol-titanium adduct could generate a C(sp3) radical for Giese-type reactions constructing C(sp3)À C(sp3) bonds. [27][28][29][30][31][32][33] Oxidative addition of low-valent Ni into etheric CÀ O bonds via directing-group strategy followed by cross-coupling with alkyl Grignard leading to C(sp3)À C(sp3) bonds. [34] Based on the reported observations, it is obvious that the construction of quaternary stereogenic carbon centers realized via XECs have been less developed.…”

“…Meanwhile, there are some examples in which aliphatic alcohols or their derivatives are applied via activation of C( sp3 )−O bonds (Figure 1a). For instance, activated benzylic alcohols could undergo β‐scission or single electron transformation (SET) to form C( sp3 ) radicals for further cross‐coupling with alkyl (pseudo−) halides in nickel catalysis, [20–26] homolysis of tertiary alcohol‐titanium adduct could generate a C( sp3 ) radical for Giese‐type reactions constructing C( sp3 )−C( sp3 ) bonds [27–33] . Oxidative addition of low‐valent Ni into etheric C−O bonds via directing‐group strategy followed by cross‐coupling with alkyl Grignard leading to C( sp3 )−C( sp3 ) bonds [34] .…”

Ph3P/ICH2CH2I-promoted reductive deoxygenation of alcohols

“…Alcohols can be first activated by a Lewis acid (LA) and would then readily undergo reduction with a hydrogen source (Scheme 1B, path d). 9 Although efficient, this approach may suffer from the high moisture sensitivity of the used Lewis acid.…”