Photoredox-Catalyzed Difunctionalization of Alkenes with Sulfilimines.

Herein, we disclose a facile photoinduced difunctionalization of alkenes, enabling the synthesis of valuable ß-amino alcohols, ß-amino ethers, and 1,2-diamines with diverse nucleophiles. The protocol relies on the use of readily accessible dibenzothiophene-based sulfilimines as novel N-radical precursors, showcasing high functional-group tolerance and exclusive regioselectivity under mild reaction conditions.

An efficient and sensitive method on the identification of unsaturated fatty acids in biosamples: Total lipid extract from bovine liver as a case study.

Unsaturated fatty acids (UFAs) are fatty acids with one or more carbon-carbon double bonds (C=C). They are building blocks of structurally complex lipids. According to the position of C=C bond in the UFAs, there are multiple isomers with different physiological activities. Therefore, an accurate understanding of UFAs is essential. Combining Paternò-Büchi (PB) reaction with tandem mass spectrometry (MS/MS) analysis has been successfully used to identify unsaturated lipids in bio-samples. However, there are still some challenges, such as low reactive rate and low MS response of PB products. In this study, 3-pyridinecarboxaldehyde (3-PYA) was selected as an efficient PB reagent for the first time. According to the nitrogen rule, introduction of nitrogen did not only make the target MS and MS/MS ions to be easily identified but also increase the ionization efficiency significantly. The developed method in this study demonstrated greater efficiency and sensitivity for the identification of UFAs in total lipid extracts from bovine liver compared with other commonly used PB reagents.

Facile access to highly functionalized hydroisoquinoline derivatives via phosphine-catalyzed sequential [3+3]/[3+3] annulation.

An unprecedented sequential [3+3]/[3+3] annulation of allenoates and dienes catalyzed by phosphine has been developed, which provides novel and facile access to highly functionalized hydroisoquinoline derivatives. The reaction features a wide reaction scope and mild reaction conditions. δ-sulfonamido-allenoates, acting as a five-atom unit, represent a new synthon in the reactions of allenoates.

Sequential Phosphine-Catalyzed [4 + 2] Annulation of ß'-Acetoxy Allenoates: Enantioselective Synthesis of 3-Ethynyl-Substituted Tetrahydroquinolines.

The first enantioselective sequential phosphine-catalyzed (SPC as abbreviation) mode for the formation of tetrahydroquinolines with an ethynyl-substituted all-carbon quaternary stereogenic center is reported. In this SPC process, a novel [4 + 2] annulation process was devised employing α-substituted allenoates as C2 synthons (α-ß', 1,2-dipole) for the first time. 3-Ethynyl-substituted tetrahydroquinolines were readily prepared in good yields and high enantioselectivities.

Divergent Domino Reactions of Sulfur Ylides: Access to Functionalized Six- and Seven-Membered Nitrogen-Heterocycles.

Divergent domino annulation reactions of sulfur ylides and azadienes were developed. A wide range of functionalized benzofuran-fused six- and seven-membered nitrogen-heterocyclic compounds were prepared in moderate to excellent yields under mild conditions. It is worth noting that the crotonate-derived sulfur ylides could be used as a novel C2 synthon or C3 synthon selectively by simply transforming the base.

Sequential [1 + 4]- and [2 + 3]-Annulation of Prop-2-ynylsulfonium Salts: Access to Hexahydropyrrolo[3,2-b]indoles.

A powerful sequential [1 + 4]- and [2 + 3]-annulation has been developed using prop-2-ynylsulfonium salts and sulfonyl-protected o-amino aromatic aldimines, affording a series of hexahydropyrrolo[3,2-b]indoles in high yields. Prop-2-ynylsulfonium salts act as C2 synthons in the reaction, and fused rings containing two five-membered azaheterocycles can be constructed in a single operation with readily accessible starting materials.

Phosphine-catalyzed intramolecular Rauhut-Currier reaction: enantioselective synthesis of hydro-2H-indole derivatives.

A highly enantioselective intramolecular Rauhut-Currier reaction catalyzed by a multifunctional chiral aminophosphine catalyst was reported. A series of hydro-2H-indole derivatives that bear an all-carbon quaternary center were obtained in high yields (up to 94%), and excellent diastereo- and enantioselectivities (up to >20 : 1 dr and >99% ee). And this reaction could be performed on a gram scale using 2 mol% catalyst loading.

[3 + 2]-Annulation of Prop-2-ynylsulfonium Salts: Access to Hydroindol-5-ones Containing a Methylthio Group.

An unprecedented [3 + 2]-annulation of prop-2-ynylsulfonium salts and p-quinamines was developed, affording a series of hydroindol-5-ones with a methylthio group in moderate to good yields under mild conditions. In this reaction, the prop-2-ynylsulfonium salt acts as a novel C2 synthon and sulfide does not serve as a leaving group, which provides facile access to organosulfur compouds.

Bifunctional-Phosphine-Catalyzed Sequential Annulations of Allenoates and Ketimines: Construction of Functionalized Poly-heterocycle Rings.

A highly stereoselective sequential annulation reaction between γ-substituted allenoates and ketimines was reported. By using bifunctional N-acyl aminophosphine catalysts, poly-heterocycle rings were obtained with high stereocontrol in good to excellent yields. The desired products have four contiguous stereogenic centers (one quaternary and three tertiary carbon centers), and only one isomer was obtained in all reactions.

Sequential Annulation Domino Reaction of Sulfur Ylides and α,ß-Unsaturated Cyclic Ketimines: Synthesis of Cyclic 2-Alkenyl Aziridines.

A sequential annulation domino reaction of sulfur ylides and α,ß-unsaturated cyclic ketimines for the construction of cyclic 2-alkenyl aziridines has been developed. Readily accessible starting materials, a one-pot procedure, excellent functional group compatibility, and mild conditions make this transformation a powerful tool for the synthesis of cyclic 2-alkenyl aziridines.

Synthesis of [60]fullerene-fused tetrahydroazepinones and azepinonimines via Cu(OAc)2-promoted N-heteroannulation reaction.

A convenient and efficient Cu(OAc)2-mediated N-heteroannulation reaction of [60]fullerene with N-sulfonylated o-amino-aromatic methyl ketones or O-alkyl oximes has been reported for the synthesis of novel and scarce [60]fullerene-fused tetrahydroazepinones and -azepinonimines in a highly selective manner. Moreover, a possible mechanism involving two pathways is proposed on the basis of the experimental observations.