Ligand- and Additive-Controlled Pd-Catalyzed Aminocarbonylation of Alkynes with Aminophenols: Highly Chemo- and Regioselective Synthesis of α,β-Unsaturated Amides

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-<i>tert</i>-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 <i>p</i>-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

Highly Ligand-Controlled Regioselective Pd-Catalyzed Aminocarbonylation of Styrenes with Aminophenols

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 (<b>L3</b>) 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 (<b>L5</b>). 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

Chemo- and Regioselective Assembly of Polysubstituted Pyridines and Isoquinolines from Isocyanides, Arynes, and Terminal Alkynes

We have disclosed a general and efficient synthetic strategy for polysubstituted pyridines and isoquinolines with high chemo- and regioselectivity. In this methodology, 1-alkynyl imines act as the key compound to undergo a sequential alkynyl imine–allenyl imine isomerization/aza-Diels–Alder reaction/aromatization. In the first place, 1-alkynyl imines were formed in situ by a highly selective multicomponent reaction of isocyanides, arynes, and terminal alkynes and reacted with another molecule of arynes or terminal alkynes to furnish target heterocyclic products in a highly efficient and atom-economic manner. On the other hand, we attempted to prepare 1-alkynyl imines by other approaches to undergo a similar reaction sequence to afford polysubstituted pyridines and isoquinolines with a wider range. Different from the first approach, the second approach utilized the preprepared 1-alkynyl imines to introduce the related different substitutents into the final products: arynes or terminal alkynes bearing substituents different from those of 1-alkynyl imines have been successfully applied for the synthesis a wide variety of pyridines and isoquinolines with diversity

Chemo- and Regioselective Assembly of Polysubstituted Pyridines and Isoquinolines from Isocyanides, Arynes, and Terminal Alkynes

We have disclosed a general and efficient synthetic strategy for polysubstituted pyridines and isoquinolines with high chemo- and regioselectivity. In this methodology, 1-alkynyl imines act as the key compound to undergo a sequential alkynyl imine–allenyl imine isomerization/aza-Diels–Alder reaction/aromatization. In the first place, 1-alkynyl imines were formed in situ by a highly selective multicomponent reaction of isocyanides, arynes, and terminal alkynes and reacted with another molecule of arynes or terminal alkynes to furnish target heterocyclic products in a highly efficient and atom-economic manner. On the other hand, we attempted to prepare 1-alkynyl imines by other approaches to undergo a similar reaction sequence to afford polysubstituted pyridines and isoquinolines with a wider range. Different from the first approach, the second approach utilized the preprepared 1-alkynyl imines to introduce the related different substitutents into the final products: arynes or terminal alkynes bearing substituents different from those of 1-alkynyl imines have been successfully applied for the synthesis a wide variety of pyridines and isoquinolines with diversity

Poverty concentration in an affluent city: Geographic variation and correlates of neighborhood poverty rates in Hong Kong

<div><p>Previous investigations of geographic concentration of urban poverty indicate the contribution of a variety of factors, such as economic restructuring and class-based segregation, racial segregation, demographic structure, and public policy. However, the models used by most past research do not consider the possibility that poverty concentration may take different forms in different locations across a city, and most studies have been conducted in Western settings. We investigated the spatial patterning of neighborhood poverty and its correlates in Hong Kong, which is amongst cities with the highest GDP in the region, using the city-wide ordinary least square (OLS) regression model and the local-specific geographically weighted regression (GWR) model. We found substantial geographic variations in small-area poverty rates and identified several poverty clusters in the territory. Factors found to contribute to urban poverty in Western cities, such as socioeconomic factors, ethnicity, and public housing, were also mostly associated with local poverty rates in Hong Kong. Our results also suggest some heterogeneity in the associations of poverty with specific correlates (e.g. access to hospitals) that would be masked in the city-wide OLS model. Policy aimed to alleviate poverty should consider both city-wide and local-specific factors.</p></div

LISA maps of the independent variables of 1,620 LSBs in Hong Kong, 2011 (data in S4 File).

<p>LISA maps of the independent variables of 1,620 LSBs in Hong Kong, 2011 (data in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0190566#pone.0190566.s004" target="_blank">S4 File</a>).</p

Organocatalyzed Enantioselective Mannich Reaction of Pyrazoleamides with Isatin-Derived Ketimines

The first organocatalytic enantioselective Mannich reaction of pyrazoleamides with isatin-derived <i>N</i>-Boc ketimines has been developed to afford 2-oxindole-based chiral β-amino amides in good yields (84–97%) with excellent diastereo- and enantioselectivities (up to 99:1 dr and >99% ee)

Mapping the poverty rates (%) of 1,620 LSBs in Hong Kong, 2011 (data in S2 File).

<p>Mapping the poverty rates (%) of 1,620 LSBs in Hong Kong, 2011 (data in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0190566#pone.0190566.s002" target="_blank">S2 File</a>).</p

Map of Hong Kong (data in S1 File).

<p>Map of Hong Kong (data in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0190566#pone.0190566.s001" target="_blank">S1 File</a>).</p

Local <i>R</i>² calculated from the GWR model of the correlates of neighborhood poverty rate in Hong Kong (data in S5 File).

<p>Local <i>R</i>² calculated from the GWR model of the correlates of neighborhood poverty rate in Hong Kong (data in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0190566#pone.0190566.s005" target="_blank">S5 File</a>).</p