Synlett

Chiral guanidine-catalyzed desymmetrization of meso-indan-1,3-diols was achieved via enantioselective silylation by using chlorosilanes in good yields with high selectivity. The combination of chlorosilanes and catalysts was determined by the substituents at the C-2 position on the substrate. It was found that the fused phenyl ring on the substrate was essential for achieving high selectivity. The proposed method was found to be applicable to several types of substrates under optimized reaction conditions. Double silylative kinetic resolution with additive Horeau amplification was observed to establish high selectivity.

Nitroaromatic compounds, as hazardous industrial pollutants, have long been extensively studied for their conversion into high-value aromatic amines. However, most of these transformation reactions require either transition-metal catalysts or high-temperature conditions. Therefore, we report an electrochemical approach utilizing pinacolborane as the reducing agent for the efficient reduction of nitroaromatic compounds. The reaction is characterized by its mild conditions and simplicity of operation, and it demonstrates excellent substrate adaptability and functional group compatibility.

α-Amino ketones were synthesized by a Meinwald rearrangement of biomass-based amino epoxides using copper(II) triflate as a catalyst. The regioselectivity of the rearrangement can be rationalized in terms of the reaction proceeding via the most stable carbocationic intermediate to give various α-amino α′-aryl ketones in moderate to good yields. This is an attractive method to prepare α-amino ketones using a benign and inexpensive catalyst.

A general strategy was developed for synthesizing 2-C-glycals through a nickel-catalyzed cross-electrophile coupling reaction of 2-iodoglycals with (hetero)aryl iodides. Key to the success of this methodology is the use of an electron-deficient bipyridyl ligand. This innovative approach facilitates the efficient construction of 2-C-glycals, thereby broadening the synthetic repertoire available for glycochemistry.

We report a mild method for the preparation of Fmoc-protected dipeptides containing a 2,4-dimethoxybenzyl (DMB) or 2-hydroxy-4-methoxybenzyl (HMB) group or modified as pseudoprolines. To minimize the loss of the Fmoc protection, we optimized the saponification conditions and included a calcium additive that protected the other base-sensitive functionalities and improved the yield of the free acid (36–82%). The reaction requires a combination of CaCl2 and NaOH in a mixture of iPrOH and water at room temperature.

A one-pot synthetic protocol to access a diverse library of diamide–diester macrocycles from the same starting materials is reported. The molecular symmetry can be readily tuned based on the reaction sequence, while the core structure can be varied using amino acids and aromatic building blocks. The first class of macrocycles with C2 axes in their molecular plane were obtained in 24 h with 40–70% yield, while another class with C2 axes perpendicular to the plane were synthesized in 18 h in 10–30% yield. The phenyl- and serine-derived macrocycles of the first class could bind acetate, chloride, and phosphate ions. These macrocycles can be functionalized with hydrophobic groups and potentially be used as ion transporters.

A catalyst- and solvent-free procedure has been developed for the synthesis of p-[( benzothiazolylamino)(aryl/heteroaryl)methyl]-functionalized phenols and its O-tosylates via one-pot three-component coupling reaction of thymol or carvacrol, aryl/heteroaryl aldehydes, and 2-aminobenzothiazoles with high selectivity. The present amino methylation process is convenient to perform even on large scale with a broad scope. The products were likely formed through the initial para attack of thymol on aldehydes to generate p-quinone methide intermediate and subsequent 1,6-aza-Michael addition of 2-aminobenzothiazoles on in-situ generated p-quinone methide intermediate.

An organocatalyzed Fischer indolization is established by combining 2,2′-biphenol (10 mol%) and B(OH)3 (30 mol%) as weak, readily available, and easy-to-handle acids. The inclusion of MgSO4, which efficiently scavenges NH3 (a possible acid catalyst poison), appears to be key to the success of this process. The corresponding indoles are obtained in yields of up to 91% using this method.y

An organocatalyzed Fischer indolization is established by combining 2,2′-biphenol (10 mol%) and B(OH)3 (30 mol%) as weak, readily available, and easy-to-handle acids. The inclusion of MgSO4, which efficiently scavenges NH3 (a possible acid catalyst poison), appears to be key to the success of this process. The corresponding indoles are obtained in yields of up to 91% using this method.y

Thioxanthone has long been a prominent catalyst in the field of photocatalysis, owing to its high triplet energy and long triplet lifetime that render it suitable for energy transfer reactions. However, its low oxidation potential and short singlet lifetime have posed challenges when employing it for electron-transfer reactions. This account summarizes our efforts in developing a potent and long-lived thioxanthone-TfOH complex (9-HTXTF) catalyst, and its application in energy-demanding redox transformations such as organophotocatalytic or electrophotocatalytic reduction and functionalization reactions.1 Introduction2 Discovery and Properties of the Catalyst 9-HTXTF3 Organophotocatalysis4 Electrophotocatalysis5 Conclusion