Enallenylamides have been utilized for the synthesis of heterobicycle[4.2.0]octane derivatives via Ir/hν promoted [2+2] cycloaddition reaction. The reaction specifically targets the distal double bond of the allene moiety, and results in the exclusive formation of the trans product. The process is conducted at room temperature and under an inert atmosphere. An extensive study on the substituent propensities during the cycloaddition step revealed variable effects. Electron-withdrawing groups conjugated with the double bond participating in the cycloaddition either hindered the process or reduced its yield. Conversely, electron-donating substituents enhanced the efficiency, resulting in product yields ranging from 60% to 88%. Our study also demonstrated the influence of protecting groups on the reaction pathway.

An original uncatalyzed three-component reaction employing mixed aliphatic organozinc reagents for the preparation of α-substituted β-ketoesters is described. This modular procedure, which relies on a formal conjugate addition/crossed-Claisen domino reaction between an organozinc, an acrylate and an acyl chloride, allows the straightforward synthesis of the reaction products under mild conditions. The three-component coupling can also be conducted from alkyl iodides, in an even more simple procedure. Experimental findings account for a probable polar concerted mechanism involving at least two organozinc compounds at the stage of the transition state.

A I2–DMSO mediated approach to introduce −OCD3 into pyrroles in situ via multicomponent cascade cyclization reaction using methyl ketones, aniline, ethyl benzoylacetate and CD3OD as readily available substrates is reported. This process realizes introduction of −OCD3 into the Hantzsch pyrrole synthesis and synthesis of deuterated alkoxy-substituted pyrroles with formation of one C–C bond, one C–O bond and two C–N bonds in one pot. Notably, this conversion has good substrate compatibility (62 examples) and eliminates of the need for anhydrous and anaerobic operation.

Visible-light photoredox-catalyzed metal-free one-pot tandem regioselective synthesis of C4-phosphorylated phthalazin-1(2H)-ones from arylhydrazines, 2-formylbenzoic acids with diarylphosphine oxides has been described. This three-component transformation occurs smoothly under mild conditions, providing the regiospecific access to various phosphorylated products in 73-91% yields. The efficacy of the current catalysis arises from the use of organic 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) as the photocatalyst and cheap K2S2O8 as the oxidant.

Propargylic alcohols are readily available bifunctional (alkyne and hydroxyl groups) synthons, which recognize as one of the attractive synthetic feedstock in organic transformations. Especially, in recent years the employment of these valuable molecules has frequently been observed in the literature. Hence, the present review highlights recent advancements in the application of propargylic alcohols in the cyclization, substitution and addition reactions.

A photoredox-catalyzed umpolung strategy for the synthesis of homoallylamines from unactivated imines and allyl bromides is described. This strategy exploited N,N-diisopropylethylamine (DIPEA) as an auxiliary agent to indirectly realize the cross-coupling of imines and allyl bromides. Various sterically hindered homoallylamines were synthesized by combining photocatalysis with halogen atom transfer (XAT). Notable characteristics of this approach include water-insensitive reaction conditions, high yield (up to 99%), wide substrate scope (suitable for N-aryl/alkyl and C-aryl ketimines and aldimines, 39 examples), and high tolerance of functional groups (such as cyano, ester, amide, and thioamide).

L-Prolinethioamide catalysed direct stereoselective glycosylation of glycal donors to access 2-deoxyglycosides under moderate reaction condition. This proposed glycosylation protocol produced the desired products with upto 88% yields and shows greater tolerance of glycosyl acceptors, broad substrate scope with better stereoselectivity. This method is also applicable for less nucleophilic acceptors such as phenol. In addition, 1,1′-linked trehalose-type analogues can also be accessed through this methodology. Further, mechanistic studies suggest that in this glycosylation L-prolinethioamide operate via Brønsted acid/base catalysis.

Gold-catalyzed cascade reactions between 1,5-diyn-3-ols and nitrones to deliver carbazole derivatives are described. Such cascade reactions are applicable to facile synthesis of polyaromatic compounds containing carbazole subunits. Notably, the reaction mechanism involves unexpected oxoarylations, rather than oxidative Mannich reactions as known for but-1-yn-4-ols. Our control experiments indicate that the presence of a second alkyne as in 1,5-diyn-3-ols enables such oxoarylations due to a weak bonding between gold and this alkyne, rending the tethered alcohol less conformationally flexible.

Copper catalysts containing alkoxydiaminophosphine (ADAP) ligand catalyze the selective C3-H functionalization of unprotected indoles upon carbene transfer from donor-acceptor diazo compounds, the N-H bond remaining unaltered during the transformation. Mechanistic studies, including DFT calculations, allows proposing the existence of two competitive pathways, none of the occurring through the formation of cyclopropane intermediates, at variance with previously reported systems.

The potential of phosphites as nucleophiles for the synthesis of chiral chromene derivatives has been overlooked in the literature. Herein, we report a promising approach via asymmetric organocatalyzed phospha-Michael addition to iminochromenes, using a bifunctional squaramide, which gives access to chromenylphosphonates, an interesting family of bioactive compounds. Our optimized protocol provides very good reactivity, affording yields of up to 95% and with chiral products exhibiting an enantiomeric excess of up to 98%.

Herein, Bi(OTf)3-catalyzed Friedel-Crafts-type annulation of sulfonyl o-hydroxyacetophenones with benzofused cycloethers is described. This single-step strategy provides a variety of functionalized dibenzofused medium-size (9–12) oxacycles through the formation of carbon-carbon and carbon-oxygen single bonds. Further, the oxidative application of target oxacycles was investigated. The chemical structures of the key products were determined based on the single-crystal X-ray analysis. In the overall process, water was generated as the byproduct.

High-valent Cu(III) trifluoromethyl complexes with 1,3-diketonates as bidentate oxygen donor ligands LCuIII(CF3)2 were prepared for the first time and fully characterized, including by X-ray crystallography. These complexes are bench stable and soluble in most organic solvents. Promising reactivity of Cu(III) trifluoromethyl diketonates in radical and radical–polar crossover trifluoromethylation reactions was demonstrated. Direct C–H trifluoromethylation of electron-rich arenes and indoles using Cu(III) trifluoromethyl diketonates under blue light irradiation is described. Azolo- and oxy-trifluoromethylation of terminal alkynes and S-trifluoromethylation of aromatic thiol can be achieved using LCuIII(CF3)2 in mild conditions.

(β-Diazo-α,α-difluoroethyl)phosphonates have been emerging as useful building blocks in organic synthetic chemistry in recent years, which can be used as diazo analog or masked carbene for the rapid assembly of difluoromethylene phosphonate-containing compounds. Herein, we elaborate a method for the synthesis of α-fluoro-β-ketophosphonates from hydration/C–F bond cleavage of in situ generated (β-amino-α,α-difluoroethyl)phosphonates via a Rh-carbene intermediate. Divers (β-amino-α,α-difluoroethyl)phosphonates are tolerated in this reaction affording α-fluoro-β-ketophosphonates in good yields. This reaction used the in situ generated water as the coupling partner, which represents a reaction of (β-diazo-α,α-difluoroethyl)phosphonates and also a method for generating bioactive α-fluoro-β-ketophosphonates.

A variety of functionalized 2-pyrrolidinones bearing N-trifluoromethylphenyl moieties were prepared in moderate to good yields with high diastereoselectivity through copper(II)-catalyst and base co-catalyzed formal [4+1] cycloaddition of cinnamaldehyde nitrones with 1-ethynylnaphthalen-2-ols in the presence of m-CPBA as the oxidant. The triple bond of 1-ethynylnaphthalen-2-ol served as one-carbon synthon for the pyrrolidinone ring formation. Mechanistic studies revealed that m-CPBA played an important role to interrupt the intramolecular O-cyclization to afford the 2-pyrrolidinones. Moreover, the reaction could be easily performed at gram scales and the obtained products were selectively converted into diverse pyrroline scaffolds.

In the last fifteen years, the development of visible-light photocatalysis, metal/photoredox dual catalysis has become the forefront as a new paradigm in organic synthesis as well as in carbohydrate chemistry. It led to the discovery of unprecedented transformations and also the improvement of known reactions under mild conditions, employing simple household light sources and bench-stable precursors, which meet the requirements of green chemistry and sustainable development in excellent yield and stereocontrol. In a general sense, the exploitation of photoredox catalysis hinges on the capability of photocatalyst or redox mediator to transform visible light into chemical energy via photo-irradiated SET (single electron transfer), PET (photoinduced electron transfer), HAT (hydrogen atom transfer), and XAT (halogen atom transfer) to potentially unlock unique reaction pathways, thereby generating a diverse array of reactive intermediates. In view of reaction type, mechanism, and status, this review will systematically summarize the latest advances in visible-light-promoted photocatalytic glycosylation reactions, which are driven by single or dual photoredox catalysis and by the photoactivity of electron donor-acceptor (EDA) complexes.

An azidobenziodoxole (BIN3)-mediated tunable radical reaction system for selective chlorination and bromination of tertiary and secondary C(sp3)−H bonds of alkyl substrates using haloform as the halogen donor was developed. Reactions of various substrates with BIN3 under visible light irradiation without any photo or metal catalysts gave C−H chlorinated or brominated products. These reactions are selective, and compatible with many functional groups. Mechanistic studies suggest that haloform serves as the halogen atom donor and HN3 generated in situ from the reaction of BIN3 and water relays the radical chain reaction as the hydrogen atom donor. HN3 reacts with CHX2⋅ to form CH2X2 and N3⋅, which propagates a radical chain by abstracting a hydrogen atom of the alkane substrate.

Application of a binary Ga-based catalyst system for the coupling of CO₂ and aziridines to form oxazolidinones is presented. It has been possible to optimize the catalyst system for the selective formation of a single regioisomer, in excellent yield, under relatively mild reaction conditions. The optimized catalyst system has been successfully applied to a range of substituted aziridines derived from styrene oxide. It has been observed that aziridines bearing two aromatic substituents result in piperazine formation through an unexpected dimerization reaction. These piperazine products can be selectively formed in the absence of CO₂ or are favoured at lower reaction temperatures. A detailed DFT study into the reaction mechanism for the formation of both products has been carried out and an unusual ligand assistance in the case of oxazolidinone synthesis has been identified. More specifically, this ligand interaction promotes the initial ring-opening of the aziridine and this work presents the first fully elucidated mechanism involving this intermediate.

Herein, a visible light-mediated multicomponent radical cross-coupling reaction of [1.1.1]propellane with N-heterocycles and disulfides is described. The mild conditions enabled the installation of the BCP motif in a wide variety of compounds in the absence of photocatalyst, additive and metal catalyst, with excellent functional group tolerance, This methodology opens a approach for the synthesis of potentially bioactive 1-arylthiol-3-heteroaryl bicyclo[1.1.1]pentanes in moderate to good yield.

α,β-Unsaturated enones possessing an unactivated olefin at the ε-, ζ- or η-position underwent an aluminum chloride-promoted Conia-ene-related cyclization, affording unsaturated decalones or hexahydroindenones in generally good yields. Cyclopropanes could be used as olefin surrogates in this process, leading to the same bicyclic products in slightly improved efficiency as the result of 1,2- or 1,3-hydroalkenylation reactions. This method provided an access to a whole range of bi- or tricyclic enone synthons, some of which were potentially useful as odorants or in the synthesis of biologically active molecules.

Gold-catalyzed interplay between ynamides and aminocarbonyls comprises a route to 2-aminoquinolines. This modular annulation proceeds under relatively mild conditions (Ph3PAuCl/AgNTf2 5 mol %, DCE, 60–80 °C), and a number of functionalities were compatible (42 examples; 25–98% yields). In contrast to a group of other gold-catalyzed methods employing the ynamide/amine combinations for the assembly of 2-aminoquinolines, the developed approach utilizes a diversity of aminocarbonyl substrates and, in particular, allows a variation of the substituents in the 4th quinoline position. The synthetic potential of the obtained heterocyclic products was illustrated by post-modifications of the quinoline backbone and the peripheral substituents.