Employing FeCl 2 as a cheap and readily available catalyst, a facile imidization of phosphines with N-acyloxyamides is described, affording synthetically useful N-acyliminophosphoranes with high functional group tolerance. The transformation is easily performed under an air atmosphere at room temperature and could be scaled up to gram scale with a catalyst loading of 1 mol %. The iminophosphoranyl moiety in the product was further utilized as an effective directing group for controllable ortho C(sp 2 )−H bond amidations under Rh(III) catalysis.
A catalyst- and metal-free hydrogenation of azobenzenes
to hydrazobenzenes
in the presence of thioacetic acid was achieved under visible light
irradiation. The transformation was carried out under mild conditions
in an air atmosphere at ambient temperature, generating a variety
of hydrazobenzenes with yields up to 99%. The current process is compatible
with a variety of substituents and is highly chemoselective for azo
reduction when other unsaturated functionalities (carbonyl, alkenyl,
alkynyl, etc.) are contained. Preliminary mechanistic study indicated
that the transformation could be a radical process.
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 %.
An iron(II)-catalyzed nitrene transfer reaction of sulfoxides with N-acyloxyamides has been developed, leading to the efficient construction of N-acyl sulfoximines with high functional-group compatibility. The current catalytic transformation was carried out under an air atmosphere at ambient temperature and could be scaled up to gram scale with a catalyst loading of 1 mol %. Application of the methodology was demonstrated by facile C−H acetoxylation and olefination using the N-acyl sulfoximine as the directing group.
An asymmetric hydrosilylation of α-oxygenated ketones was developed under the catalysis of Co(OAc) 2 in combination with a chiral phosphine-amido-oxazoline (PAO) ligand, providing a mild, efficient, and enantioselective access to a variety of synthetically useful 1,2-diol derivatives. This protocol can be carried out at the gram scale with a catalyst loading of 1 mol %, and its synthetic utility was demonstrated by efficient conversion of the optically enriched products into chiral α-hydroxy acid, 1,3dioxolan-2-one, ethylene oxide, and 1,2,3-1H-triazole.
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