Cyclic Dipeptides Formation From Linear Dipeptides Under Potentially Prebiotic Earth Conditions

Cyclic dipeptides (DKPs) are peptide precursors and chiral catalysts in the prebiotic process. This study reports proline-containing DKPs that were spontaneously obtained from linear dipeptides under an aqueous solution. Significantly, the yields of DKPs were affected by the sequence of linear dipeptides and whether the reaction contains trimetaphosphate. These findings provide the possibility that DKPs might play a key role in the origin of life.

Access to enantioenriched compounds bearing challenging tetrasubstituted stereocenters via kinetic resolution of auxiliary adjacent alcohols

Contemporary asymmetric catalysis faces huge challenges when prochiral substrates bear electronically and sterically unbiased substituents and when substrates show low reactivities. One of the inherent limitations of chiral catalysts and ligands is their incapability in recognizing prochiral substrates bearing similar groups. This has rendered many enantiopure substances bearing several similar substituents inaccessible. Here we report the rationale, scope, and applications of the strategy of kinetic resolution of auxiliary adjacent alcohols (KRA*) that can be used to solve the above troubles. Using this method, a large variety of optically enriched tertiary alcohols, epoxides, esters, ketones, hydroxy ketones, epoxy ketones, β-ketoesters, and tetrasubstituted methane analogs with two, three, and four spatially and electronically similar groups can be readily obtained (totally 96 examples). At the current stage, the strategy serves as the optimal solution that can complement the inability caused by direct asymmetric catalysis in getting chiral molecules with challenging fully substituted stereocenters.

Thiophene fused indenocorannulenes: synthesis, variable emission, and exceptional chiral configurational stability

Graph theory and isosteric replacement leads to the design and synthesis of (chiral) thiophene-fused indenocorannulenes with exceptional configurational stability and possible use as chiral catalysts, chiroptical materials, and sensors.

Kinetic Insights into Cyanosilylation of Aldehydes Catalyzed by a Covalently Bridged Dinuclear (Salen)titanium Complex

Enantioselective addition of trimethylsilyl cyanide (TMSCN) to aldehydes is one of the most extensively studied organic reactions in asymmetric catalysis. Herein, we report our intensive kinetic investigation on the asymmetric addition of TMSCN to benzaldehyde, catalyzed by a covalently bridged dinuclear (salen)titanium complex <b>2</b>, which has been one of the most efficient artificial chiral catalysts reported so far for this reaction. It was found that the method of initial rates for kinetic investigation is not appropriate in this case because of the presence of a significant <a></a><a>incubation </a>period in the catalysis, while the method of progress rates proved to be more reliable and efficient for judging the kinetic orders of this catalytic system. The kinetic results revealed that <a>the reaction follows first order with respect to the catalyst</a> and is nearly independent of concentrations of both benzaldehyde and TMSCN<a>. A detailed catalytic mechanism for cyanosilylation of benzaldehyde in the presence of <b>2</b> was proposed, wherein the key active dinuclear species works in a cooperative manner for dual activation of both reactants.</a>

Kinetic Insights into Cyanosilylation of Aldehydes Catalyzed by a Covalently Bridged Dinuclear (Salen)titanium Complex

Enantioselective addition of trimethylsilyl cyanide (TMSCN) to aldehydes is one of the most extensively studied organic reactions in asymmetric catalysis. Herein, we report our intensive kinetic investigation on the asymmetric addition of TMSCN to benzaldehyde, catalyzed by a covalently bridged dinuclear (salen)titanium complex <b>2</b>, which has been one of the most efficient artificial chiral catalysts reported so far for this reaction. It was found that the method of initial rates for kinetic investigation is not appropriate in this case because of the presence of a significant <a></a><a>incubation </a>period in the catalysis, while the method of progress rates proved to be more reliable and efficient for judging the kinetic orders of this catalytic system. The kinetic results revealed that <a>the reaction follows first order with respect to the catalyst</a> and is nearly independent of concentrations of both benzaldehyde and TMSCN<a>. A detailed catalytic mechanism for cyanosilylation of benzaldehyde in the presence of <b>2</b> was proposed, wherein the key active dinuclear species works in a cooperative manner for dual activation of both reactants.</a>

Recent Advances in Catalytic Synthesis of Benzosultams

Benzosultams represent one category of multi-heteroatom heterocyclic scaffolds, which have been frequently found in pharmaceuticals, agricultural agents, and chiral catalysts. Given the diversely significant functions of these compounds in organic and medicinal chemistry, great efforts have been made to develop novel catalytic systems for the efficient construction of benzosultam motifs over the past decades. Herein, in this review, we mainly summarize the recent advances in the field of catalytic synthesis of benzosultams from 2017 to August of 2020, with an emphasis on the scopes and mechanisms of representative reactions.