Ion-Pair Extraction with Tetracyanocyclopentadienides: A Method for Estimating Extraction Efficiency

Ion-pair extraction with tetracyanocyclopentadienides (TCCPs) is an effective method for isolating ammonium cations; however, predicting the extractability of ammonium-TCCP ion pairs is challenging. Herein, the measured extraction coefficients (LogKex) of ammonium-TCCP ion pairs allowed the values of A (an index for anion extractability) for the TCCP anions to be determined (-3.1 to -1.4); these values were higher than and similar to those of perchlorate and picrate anions, respectively. The correlation between LogKex and the sum of the values of A and the calculated Log P of ammonium cations revealed that LogKex can be estimated by the equation LogKex = A + CLOGPNR4 + 1.6, where CLOGPNR4 is the CLOGP value obtained using the "no-plus" ammonium structure. The LogKex value can be used to predict the extractability of quaternary ammonium ions.

Easy access to α-carbonyl sulfones using cross-coupling of α-aryl-α-diazoesters with sulfonyl hydrazides

A facile synthesis of α-carbonyl sulfones has been accomplished by the cross-coupling of α-aryl-α-diazoesters with sulfonyl hydrazides in the presence of CuI and DBU. The reaction employs inexpensive and bench stable sulfonyl hydrazides as a sulfonyl source, and facilitates the migratory insertion with α-aryl-α-diazoesters under mild reaction conditions.

Copper(I)-Catalyzed Cross-Coupling of Arylsulfonyl Radicals with Diazo Compounds: Assembly of Arylsulfones

A novel copper-catalyzed cross-coupling of arylsulfonyl radicals with diazo compounds is described for the synthesis of various arylsulfones under mild conditions. In this reaction, the cheap, environmentally friendly, and readily available inorganic K₂S₂O₅ is employed as the sulfur dioxide source for providing arylsulfonyl radicals. In addition, a radical mechanism involving the insertion of sulfur dioxide with aryl radicals followed by the coupling of arylsulfonyl radicals with copper carbenes is proposed.

Dioxygen-Triggered Oxosulfonylation/Sulfonylation of Terminal Olefins toward β-Keto Sulfones/Sulfones

A dioxygen-triggered oxosulfonylation/sulfonylation of unactivated olefins to achieve β-keto sulfones/sulfones has been developed. Interestingly, pluralistic mechanisms were found when different types of compounds were applied as substrates, and different products were achieved. The reaction is carried out with a high atomic efficiency in the absence of a metal and a catalyst at room temperature under an air atmosphere. Importantly, as a proof-of-concept, a bioactive molecule was synthesized on a gram-scale level using this method.

Copper-Mediated Cross-Coupling of Diazo Compounds with Sulfinates

A copper-mediated cross-coupling reaction between a diazo compound and a sodium alkane(arene)sulfinate gives a sulfone as the product. This reaction proceeds under mild conditions and features excellent functional group compatibility. A wide range of sodium alkane(arene)sulfinates were successfully applied in this chemistry. Mechanistic studies revealed that the overall reaction efficiency of the sulfinates was in line with their nucleophilicity in this reaction.

Recent advances in the synthesis and applications of β-keto sulfones: new prospects for the synthesis of β-keto thiosulfones

This review mainly focuses on recent developments in the preparation of β-keto sulfones and their extensive synthetic applications. New prospects for the synthesis of β-keto thiosulfones have also been highlighted. Over the last decade, there has been exponential growth in the direct construction of β-keto sulfones using a wide variety of keto and sulfonyl precursors. Of note, the most promising photoredox transformations and electrochemical synthesis methods of β-keto sulfones are also presented. Moreover, β-keto sulfones are versatile building blocks in organic synthesis due to their three essential functional groups: sulfonyl, carbonyl, and active methylene moieties. The convenient preparation of β-keto sulfones allows the synthesis of many valuable carbocyclic and heterocyclic compounds, and the effortless removal of the sulfonyl moiety via transformations is supported. The chemistry of β-keto sulfones (2013 to present) can be divided into several sections based on the sulfonyl surrogates, and ubiquitous synthetic strategies were systematically outlined.

Synthesis and applications of sodium sulfinates (RSO2Na): a powerful building block for the synthesis of organosulfur compounds

This review highlights the preparation of sodium sulfinates (RSO2Na) and their multifaceted synthetic applications. Substantial progress has been made over the last decade in the utilization of sodium sulfinates emerging as sulfonylating, sulfenylating or sulfinylating reagents, depending on reaction conditions. Sodium sulfinates act as versatile building blocks for preparing many valuable organosulfur compounds through S-S, N-S, and C-S bond-forming reactions. Remarkable advancement has been made in synthesizing thiosulfonates, sulfonamides, sulfides, and sulfones, including vinyl sulfones, allyl sulfones, and β-keto sulfones. The significant achievement of developing sulfonyl radical-triggered ring-closing sulfonylation and multicomponent reactions is also thoroughly discussed. Of note, the most promising site-selective C-H sulfonylation, photoredox catalytic transformations and electrochemical synthesis of sodium sulfinates are also demonstrated. Holistically, this review provides a unique and comprehensive overview of sodium sulfinates, which summarizes 355 core references up to March 2020. The chemistry of sodium sulfinate salts is divided into several sections based on the classes of sulfur-containing compounds with some critical mechanistic insights that are also disclosed.