of Catalysis at Dalian Institute of Chemical Physics. His research interests include (1) CO 2 hydrogenation to chemicals and fuels, (2) methanol steam reforming to hydrogenation, and (3) liquid solar fuel synthesis.
Achieving chemo- and regioselectivity simultaneously is challenging in organic synthesis. Transition metal-catalyzed reactions are effective in addressing this problem by the diverse ligand effect on the catalyst center. Ligand-controlled regioselective Pd-catalyzed carbonylation of styrenes with aminophenols was realized, chemoselectively affording amides. Using a combination of boronic acid and 5-chlorosalicylic acid as the additives, linear amides were obtained in high yields and selectivity using tris(4-methoxyphenyl)phosphine (L3) in acetonitrile, while branched amides were obtained in high yields and selectivity in butanone by changing the ligand to 1,3,5,7-tetramethyl-2,4,8-trioxa-6-phenyl-6-phosphaadamantane (L5). Further studies show that the nature of the ligand is key to the regioselectivity. Cone angle and Tolman electronic parameter (TEP) have been correlated to the reactivity and regioselectivity. Studies on the acid additives show that different acids act as the proton source and the corresponding counterion can help enhance the reactivity and selectivity.
Many components make light work: A novel synthetic strategy for the preparation of pyridines and isoquinolines in high chemo- and regioselectivity has been developed. By manipulating the reaction conditions, either product can be generated smoothly in a highly efficient and atom-economic manner (see scheme).
This
work describes the chemo- and regioselective direct aminocarbonylation
of alkynes and aminophenols to form hydroxy-substituted α,β-unsaturated
amides in good to excellent yields. The latter are valuable compounds
in pharmaceuticals and natural products. By a simple choice of different
ligands and additives, branched or linear isomers could be selectively
formed in excellent regioselectivity. Using a combination of boronic
acid and 5-chlorosalicylic acid (“BCSA”) as the additives,
linear amides were obtained in high yields and selectivities using
1,2-bis(di-tert-butylphosphinomethyl)benzene (DTBPMB)
as the ligand. On the other hand, branched amides could be approached
by introducing 1,3-bis(diphenylphosphino)propane as the ligand and p-TsOH·H2O as the additive. In addition
to the hydroxyl group, other functional substituents, such as carboxyl
and vinyl groups, could also be tolerated using this method. As an
application of this strategy, the natural product avenanthramide A
could be synthesized directly in 84% yield and in 99% regioselectivity
via the carbonylation of 2-amino-5-hydroxybenzoic acid and 4-ethynylphenol.
Further studies show that the ligands and the additives are keys to
good yields and selectivities.
Several high-frequency RDH12 variants were identified in patients with inherited retinal dystrophies, most of which were missense mutations. Variable but characteristic phenotypes of a progressive nature was observed. Overall, the findings indicated that biallelic RDH12 mutations are a common cause of early-onset retinal dystrophy and a rare cause of cone-rod dystrophy.
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