Electrochemical chemoselective hydrogenation of 1,4-enediones with HFIP as the hydrogen donor: scalable access to 1,4-diketones.

A straightforward electrochemical protocol for efficient hydrogenation of unsaturated CC bonds has been reported in an undivided cell. A series of versatile 1,4-diketones are smoothly generated under metal-free and external-reductant-free electrolytic conditions. Moreover, the tolerance of various functional groups and decagram-scale experiments have shown the practicability and potential applications of this methodology. Moreover, a range of heterocyclic compounds were easily prepared through follow-up procedures of 1,4-diketones.

Nickel-promoted oxidative domino Csp3-H/N-H bond double-isocyanide insertion reaction to construct pyrrolin-2-ones.

The first nickel-catalyzed oxidative domino Csp3-H/N-H double isocyanide insertion reaction of acetamides with isocyanides has been developed for the synthesis of pyrrolin-2-one derivatives. A wide range of acetamides bearing various functional groups are compatible with this reaction system by utilizing Ni(acac)2 as a catalyst. In this transformation, isocyanide could serve as a C1 connector and insert into the inactive Csp3-H bond, representing an effective way to construct heterocycles.

InCl3-catalyzed 5-exo-dig cyclization/1,6-conjugate addition of N-propargylamides with p-QMs to construct oxazole derivatives.

An InCl3-catalyzed atom-economic intramolecular 5-exo-dig cyclization/1,6-conjugate addition/aromatization of N-propargylamides with p-QMs to produce oxazoles tethering diarylmethane has been successfully developed. InCl3 not only served as Lewis acid to catalyze the cyclization of propargylic amides but also activated the carbonyl of p-QMs to achieve the 1,6-addition process in a one-pot manner. The reaction has attractive features, including mild reaction conditions, broad scope of substrates, good yields, and scalability.

Fast construction of isoquinolin-1(2H)-ones by direct intramolecular C-H/N-H functionalization under metal-free conditions.

The general protocol for the synthesis of isoxazolidine-fused isoquinolin-1(2H)-ones was established with the help of bench stable hypervalent iodine reagent PIDA. Polycyclic six-, seven- and eight-membered N-heterocycles can be rapidly synthesized from available amides under metal-free conditions within 1 min at room temperature through C-H/N-H functionalization. Moreover, the protocol has the merits of broad substrate scope, atom economy and operational simplicity.

The ruthenium(ii)-catalyzed C-H olefination of indoles with alkynes: the facile construction of tetrasubstituted alkenes under aqueous conditions.

An environmentally-friendly and facile protocol for the construction of tetrasubstituted alkenes has been established with Ru(ii)-catalyzed C-H bond functionalizations under mild conditions. The method features the usage of readily available substrates, without external oxidants and additives, 100% atom economy, and excellent regioselectivity, thus enhancing the practicability of this protocol. Moreover, this transformation proceeded smoothly under aqueous conditions and could be extended to the gram scale. N-Methoxyamide, as a directing group (DG), played a vital role in the transformation.

One Base for Two Shots: Metal-Free Substituent-Controlled Synthesis of Two Kinds of Oxadiazine Derivatives from Alkynylbenziodoxolones and Amidoximes.

Different 1,2-migrations and cyclizations of a variety of alkynylbenziodoxolones (EBXs) and amidoximes under one-base conditions are described. This process provides an efficient protocol for the divergent synthesis of two oxadiazine derivatives via switchable selectivity of EBXs controlled by simply varying the substituents of the amidoximes, which feature transition metal-free conditions, simple execution, and high chemoselectivity.

N-Phenoxyamides as Multitasking Reagents: Base-Controlled Selective Construction of Benzofurans or Dihydrobenzofuro[2,3- d]oxazoles.

An efficient method to selectively construct benzofuran and dihydrobenzofuro[2,3- d]oxazole derivatives has been successfully established by means of base-controlled cyclization of N-phenoxyamides with 1-[(triisopropylsilyl)ethynyl]-1,2-benziodoxol-3(1 H)-one (TIPS-EBX). N-phenoxyamides as multitasking reagents have triggered two different cascade reaction sequences. This is the first example of using TIPS-EBX for the transformation of C(sp) to either C(sp2) or C(sp3) under metal-free conditions.

Intramolecular dehydrogenative C-S bond coupling of thioamides to form 1,3-benzothiazines under metal-free conditions.

A novel HTIB-promoted direct intramolecular dehydrogenative C-S bond coupling reaction of thioamides has been developed to provide 1,3-benzothiazine derivatives in good yields. The reaction proceeds smoothly to reach completion at room temperature within 1 min under metal-free conditions. This protocol provides a mild and efficient strategy for the synthesis of six-membered N,S-containing heterocycles. Preliminary mechanistic studies indicate that a spirocyclic intermediate might be involved.

Chemo-, Regio-, and Stereoselective Construction of Core Skeleton of Furo[2,3-b]pyrrole via Multicomponent Bicyclization Reaction.

An efficient and straightforward N-ethyldiisopropylamine (DIPEA)-catalyzed multicomponent bicyclization reaction was developed to synthesize furo[2,3-b]pyrrole derivatives from ß-ketothioamides, glyoxals, and ethyl cyanacetate in EtOH at rt for 1.5 h. This was achieved via a sequential Knoevenagel condensation, Michael addition, and double cyclization, resulting in continuous formation of four chemical bonds (two C-C, two C-O, and one C-N bonds), two five-membered cycles, and three stereogenic centers in a one-pot operation.

Synthesis of 6-Phosphorylated Phenanthridines by Mn(II)-Promoted Tandem Reactions of 2-Biaryl Isothiocyanates with Phosphine Oxides.

A novel Mn(II)-promoted tandem phosphorylation/cyclization reaction of 2-biaryl isothiocyanates with phosphine oxides is described. This is the first general method to synthesize 6-phosporylated phenanthridines from 2-biaryl isothiocyanates. The approach is featured by oxidant-free, low loading of P-reagent, easy operation, and high functional group tolerance.