Regioselective Chlorothiolation of Alkenes with Sulfonyl Chlorides.

Newly developed sulfonyl chloride-based regioselective chlorothiolation of alkenes has been disclosed; the reaction is compatible with a variety of functional groups and can be scaled up to the gram scale with no loss in yield. The employment of readily available reactants, mild reaction conditions, and high regioselectivity makes this process very practical. Mechanistic studies revealed a possible free radical reaction pathway.

Copper-Catalyzed Vicinal Chloro-thiolation of Alkynes with Sulfonyl Chlorides.

A copper-catalyzed vicinal chloro-thiolation of alkynes with inexpensive and diversified sulfonyl chlorides RSO2Cl (R = aryl, alkyl) has been developed. This practical and scalable reaction could be used for the construction of a number of unexplored bioactive chlorothiolated alkenes. Internal alkynes could also undergo the chloro-thiolation to provide tetrasubstituted alkynes. Preliminary mechanistic investigations revealed a plausible radical process involving a sulfur-centered radical intermediate via copper-mediated homolysis of the S-Cl bond.

Fluoroalkylsulfonyl Chlorides Promoted Vicinal Chloro-fluoroalkylthiolation of Alkenes and Alkynes.

The unprecedented use of CF3SO2Cl for direct bifunctional chloro-trifluoromethylthiolation of alkenes and alkynes is reported. CF3SCl, which is generated by the reduction of PPh3, undergoes electrophilic addition and then chlorination to give the bifunctionalized products without using an additional chlorine source. The method is also applicable for chloro-difluoromethylthiolation using CF2HSO2Cl.

Copper-catalyzed fluoroalkylation of alkynes, and alkynyl & vinyl carboxylic acids with fluoroalkyl halides.

Copper-catalyzed fluoroalkylation of alkynes and alkynyl carboxylic acids has been achieved with high functional-group tolerance and excellent regio- and stereoselectivities. A variety of fluoroalkyl halides including ethyl bromodifluoroacetate can be employed. Additionally, an unprecedented decarboxylative fluoroalkylation of α, ß-unsaturated carboxylic acids has been achieved via a radical pathway.

Stereoselective Synthesis of Alkenyl Silanes, Sulfones, Phosphine Oxides, and Nitroolefins by Radical C-S Bond Cleavage of Arylalkenyl Sulfides.

A radical-mediated approach has been introduced for the C-S bond activation of arylalkenyl sulfides. The protocol provides an efficient approach for the generation of various alkenes including alkenyl silanes, sulfones, phosphine oxides, and nitroolefins. In most cases, these radical substitutions are performed under metal-free conditions with stereospecificity.

Acid/Phosphide-Induced Radical Route to Alkyl and Alkenyl Sulfides and Phosphonothioates from Sodium Arylsulfinates in Water.

A newly developed aqueous system with acid and phosphide was introduced in which odorless and stable sodium arylsulfinates can in situ generate arylsulfenyl radicals. These radicals have high reactivity to react with alkynes, alkenes, and H-phosphine oxides for the synthesis of alkyl and alkenyl sulfides and phosphonothioates. The control experiments and quantum calculations are also performed to gain insights into the generation mechanism of arylsulfenyl radicals. Notably, the chemistry is free of thiol odors, organic solvents, and metals.

Radical Route to 1,4-Benzothiazine Derivatives from 2-Aminobenzenethiols and Ketones under Transition-Metal-Free Conditions.

Transition-metal-free radical access to 1,4-benzothiazine derivatives from o-aminobenzenethiols is disclosed. This procedure is available for various ketones including α,ß-unsaturated, cyclic, linear, and fluoroalkyl ketones to generate a number of 1,4-benzothiazines, which exist in numerous bioactive and natural molecules, rendering this protocol attractive to both synthetic and medicinal chemistry.

Organocatalytic One-Pot Asymmetric Synthesis of Thiolated Spiro-γ-lactam Oxindoles Bearing Three Stereocenters.

The first asymmetric synthesis of spiro-γ-lactam oxindoles bearing three stereocenters is reported. One-pot thiol-Michael/Mannich/lactamization reactions promoted by a recyclable fluorous bifunctional cinchona alkaloid/thiourea organocatalyst afford products in moderate to good yields with up to 95% ee and 6:1 dr.

A Route to α-Fluoroalkyl Sulfides from α-Fluorodiaroylmethanes.

α,α-Difluorodiaroylmethane can be used as a nucleophilic difluoromethylation reagent for generating α-thioaryl-α,α-difluoroacetophenones (Ar(1)COCF2SAr) and difluoromethylthiolated arenes (ArSCF2H) under transition-metal-free conditions. The reaction selectivity is mainly dependent on temperature. The method has also been extended to the synthesis of α-thioaryl-α-monofluoroacetophenones using α-monofluorodibenzoylmethane. Moreover, the benzoyl cation derived from α,α-difluorodibenzoylmethane can react with nucleophiles to afford the desired products in a one-pot process.

Odorless, One-Pot Regio- and Stereoselective Iodothiolation of Alkynes with Sodium Arenesulfinates under Metal-Free Conditions in Water.

A newly developed regio- and stereoselective radical addition of alkyne under metal-free conidtions has been disclosed. This chemistry, in which odorless sodium arenesulfinates in place of thiols are used as the sulfur reagent, provides an efficient, one-pot approach for the generation of ß-iodoalkenyl sulfides, which can be easily further functionalized to derive various alkenes and alkynyl sulfides rendering this methodology attractive to both synthetic and medicinal chemistry.

Transition-metal-free C-H oxidative activation: persulfate-promoted selective benzylic mono- and difluorination.

An operationally simple and selective method for the direct conversion of benzylic C-H to C-F to obtain mono- and difluoromethylated arenes using Selectfluor™ as a fluorine source is developed. Persulfate can be used to selectively activate benzylic hydrogen atoms toward C-F bond formation without the aid of transition metal catalysts.

One-pot synthesis of 2-amino-4(3H)-quinazolinones via ring-opening of isatoic anhydride and palladium-catalyzed oxidative isocyanide-insertion.

An efficient and practical two-step process has been developed for the synthesis of 2-amino-4(3H)-quinazolinones via ring-opening of isatoic anhydride and palladium-catalyzed oxidative isocyanide-insertion in one pot. This regioselective procedure could construct a wide range of 2-amino-4(3H)-quinazolinones in moderate to excellent yields. Furthermore, the methodology also had distinct advantages of easily accessible starting materials and operational simplicity.

Synthesis of highly functionalized macrocycles by tandem multicomponent reactions and intramolecular Sonogashira cross-coupling.

An efficient chemoselective process for the synthesis of 14- and 15-membered triazole-containing macrocycle compounds has been developed through the combination of two multicomponent reactions and an intramolecular Sonogashira cross-coupling reaction.

Synthesis of novel isoquinolinone and 1,2-dihydroisoquinoline scaffolds via Ugi reaction and ring opening reaction of furans.

Combining the Ugi reaction with ring opening reaction of furans for the synthesis of novel isoquinolinone and 1,2-dihydroisoquinoline scaffolds has been developed. The isoquinolinone and 1,2-dihydroisoquinoline derivatives with unsaturated carbonyl moiety may open up many opportunities for further functionalizations.

Chemoselective preparation of 1,2,3-triazole-isoxazole bisfunctional derivatives and their application in peptidomimetic synthesis.

A novel kind of bisfunctional nitrogen heterocycle containing both 1,2,3-triazole and isoxazole scaffolds has been prepared. The protocol utilized alkynyl substituted amines as the bifunctional linkers to combine a copper-free triazole synthesis with a hypervalent iodine-mediated isoxazole cycloaddition through a chemoselective process. This method has also been exemplified in the construction of bisfunctional-modified peptidomimetics by combining three reactions in a sequential procedure. This straightforward metal free process may find biological applications. In addition, all of the compounds were analysed by Lapinski's rule-of-five which is expected to help drug discovery.

Recyclable fluorous cinchona alkaloid ester as a chiral promoter for asymmetric fluorination of ß-ketoesters.

A fluorous cinchona alkaloid ester has been developed as a chiral promoter for the asymmetric fluorination of ß-ketoesters. It has comparable reactivity and selectivity to the nonfluorous versions of cinchona alkaloids and can be easily recovered from the reaction mixture by simple fluorous solid-phase extraction (F-SPE) and used for the next round of reaction without further purification.

Copper-free route to triazole-modified peptidomimetic by the combination of two multicomponent reactions in one pot.

An efficient copper-free protocol for the synthesis of 5-methyl-1H-1,2,3-triazole-modified peptidomimetics through the combination of Ugi four-component reaction with a three-component cycloaddition, has been developed. The copper-free straightforward process is suitable for drug discovery. The chemoselective preparation of 1,4-disubstituted, triazole-modified peptidomimetics by using alkynyl substituted amines may have potential biological and synthetic application. At last, a "Lapinski type" analysis of the physical properties was performed, which is expected to help drug discovery.

Thiourea based fluorous organocatalyst.

This review deals with general and significant development of the fluorous organocatalysts based on thiourea. The applications of fluorous technology are briefly discussed. The implementations of thiourea based catalysts in organic synthesis are focused on in the chapter.

[The hierarchical clustering analysis of hyperspectral image based on probabilistic latent semantic analysis].

The paper introduces the Probabilistic Latent Semantic Analysis (PLSA) to the image clustering and an effective image clustering algorithm using the semantic information from PLSA is proposed which is used for hyperspectral images. Firstly, the ISODATA algorithm is used to obtain the initial clustering result of hyperspectral image and the clusters of the initial clustering result are considered as the visual words of the PLSA. Secondly, the object-oriented image segmentation algorithm is used to partition the hyperspectral image and segments with relatively pure pixels are regarded as documents in PLSA. Thirdly, a variety of identification methods which can estimate the best number of cluster centers is combined to get the number of latent semantic topics. Then the conditional distributions of visual words in topics and the mixtures of topics in different documents are estimated by using PLSA. Finally, the conditional probabilistic of latent semantic topics are distinguished using statistical pattern recognition method, the topic type for each visual in each document will be given and the clustering result of hyperspectral image are then achieved. Experimental results show the clusters of the proposed algorithm are better than K-MEANS and ISODATA in terms of object-oriented property and the clustering result is closer to the distribution of real spatial distribution of surface.

Fluorous silica gel-supported perfluoro-tagged palladium nanoparticles: an efficient and reusable catalyst for direct C-2 arylation of indoles.

The preparation of FSG-supported palladium nanoparticles and their application in direct C-2 arylation of indoles are presented. Moderate to good yields were obtained with ultra-low catalyst loading. The catalyst could be easily recovered by simple workup and reused up to seven runs with only a slight decrease in its activity.