Cobalt-Catalyzed Z to E Geometrical Isomerization of 1,3-Dienes

Abstract

An efficient cobalt-catalyzed geometrical isomerization of 1,3-dienes is described. In the combination of a CoCl2 precatalyst with an amido-diphosphine-oxazoline ligand, the geometrical isomerization of E/Z mixtures of 1,3-dienes proceed in a stereoconvergent manner, affording (E) isomers in high stereoselectivity. This facile transformation features a broad substrate scope with good functional group tolerance and could be scaled up to the gram scale smoothly with a catalyst loading of 1 mol %.

A palladium catalyzed stereo-convergent aminocarbonylation of 1,3-dienes with nitroarenes: synthesis of (E,E)-dienamides

“…11 Thus, the development of a stereo-convergent transformation of E / Z mixtures of 1,3-dienes is highly desirable. 12 Recently, a low valence transition-metal was found to be able to serve as a π-Lewis base catalyst for the coupling of dienes with aldehyde and imine electrophiles. 13 For example, Kimura reported a Pd-catalyzed allylation of aldehydes with conjugated dienes with Et 3 B as the Lewis acid activator to obtain dienyl homoallyl alcohols.…”

Ligand-controlled cobalt-catalyzed isomerization and reductive C–O bond cleavage of allylic ethers

“…In view of the above experimental observations and previous reports, 20 the possible catalytic cycles for the cobalt-catalyzed isomerization and reductive C–O bond cleavage reactions are outlined in Scheme 4. First, the ligated cobalt-hydride species ( A ) could be formed in situ by mixing CoCl 2 and ligand with NaBHEt 3 .…”

Cobalt-Catalyzed Asymmetric Hydrosilylation of α-Oxygenated Ketones

“…Generally, the applications of these catalytic systems were restricted to simple aryl alkyl, diaryl, and dialkyl ketones (Scheme a). However, only limited attention was paid to the catalytic asymmetric hydrosilylation of α-oxygenated ketones, and the enantioselectivity was far from satisfactory in sporadic examples studied. , Very recently, we found that the combination of cobalt salt with a phosphine-amido-oxazoline (PAO) ligand showed unique catalytic activity for alkene and diene isomerization . Following our interest in related fields, in this work we disclose a cobalt-catalyzed asymmetric hydrosilylation of α-acyloxyl and α-phenoxy ketones with a chiral PAO ligand, affording a series of chiral 1,2-diol derivatives with high enantioselectivities (Scheme b).…”