Silver-Catalyzed Dibromotrifluoromethoxylation of Terminal Alkynes

Catalyst-Free Trifluoromethoxylation of Silyl Enol Ethers and Allyl Silanes with Bis(trifluoromethyl)peroxide

Radical trifluoromethoxylation is an attractive approach to prepare compounds featuring the important OCF3 group, however most existing methods have focused on aromatic substrates. Here, we report novel methodologies with alkenyl substrates employing bis(trifluoromethyl)peroxide (BTMP) as a practical and comparatively atom economical trifluoromethoxylating reagent. With silyl enol ether substrates, switching reaction solvent allows for the synthesis of either α-(trifluoromethoxy)ketone products or unprecedented alkenyl-OCF3 species. Furthermore, allyl silanes have been employed as substrates for the first time, affording allyl(trifluoromethyl)ether products in good yields. In each case, the methods operate at room temperature without large excesses of the alkene substrate while, in contrast to previous radical trifluoromethoxylation reactions, no catalyst, light or other activators are required.

Silver-Enabled Dearomative Trifluoromethoxylation of Indoles

The only known method for the dearomative trifluoromethoxylation of indoles is preliminary, with only one substrate successfully undergoing the reaction. In this study, we not only developed a broadly applicable method for indole dearomative trifluoromethoxylation but also achieved divergent trifluoromethoxylation by fine-tuning the reaction conditions. Under optimized conditions, with a silver salt and an easily handled OCF3 reagent, various indoles smoothly underwent dearomatization to afford a diverse array of ditrifluoromethoxylated indolines in 50-84% isolated yields with up to 37:1 diastereoselectivity, and fluorinated trifluoromethoxylated indolines were obtained with exclusive trans selectivity. In addition, the reaction conditions were compatible with other heteroaromatic rings as well as styrene moieties.

Synthesis of silver and gold nanoparticles-enzyme-polymer conjugate hybrids as dual-activity catalysts for chemoenzymatic cascade reactions

Novel hybrids containing silver or gold nanoparticles have been synthesized in aqueous media and at room temperature using enzymes or tailor-made enzyme-polymer conjugates, which directly induced the formation of inorganic silver or gold species. The choice of pH, protein, or bioconjugate strongly affected the final metallic nanoparticles hybrid formation. Using Candida antarctica lipase (CALB) in a solution, nanobiohybrids containing Ag₂O nanoparticles of 9 nm average diameter were obtained. The use of tailor-made bioconjugates, for example, the CALB modified with dextran-aspartic acid polymer (Dext6kDa), resulted in a nanobiohybrid containing smaller Ag(0)/Ag₂O nanoparticles. In the case of nanobiohybrids based on gold, Au(0) species were found in all cases. The Au-CALB hybrid contained spherical nanoparticles with 18 nm average diameter size, with a minor range of larger ones (>100 nm) while the AuNPs-CALB-Dext6kDa hybrid was formed by much smaller nanoparticles (9 nm, minor range of 22 nm), and also nanorods of 20-30/40-50 nm length. Using Thermomyces lanuginosus lipase (TLL), apart from the nanoparticle formation, nanoflowers with a diameter range of 100-200 nm were obtained. All nanobiohybrids maintained (dual) enzymatic and metallic activities. For instance, these nanobiohybrids exhibited exquisite dual-activity for hydrolysis/cycloisomerization cascades starting from allenic acetates. By merging the transition metal reactivity with the inherent lipase catalysis, allenic acetates directly converted to the corresponding O-heterocycles in enantiopure form catalysed by AgNPs-CALB-Dext6kDa, taking advantage of a kinetic resolution/cyclization pathway. These results showed the high applicability of these novel hybrids, offering new opportunities for the design of novel reaction cascades.

AgNTf2-Catalyzed Regioselective C-H Alkenylation of N,N-Dialkylanilines with Ynamides

Regioselective C-H alkenylation of N,N-dialkylanilines with ynamides was developed using AgNTf₂ as a catalyst. This approach represents a facile hydroarylation of ynamides, allowing for the introduction of an alkenyl group exclusively at the para position of aniline derivatives. As a result, a series of 4-alkenyl N,N-dialkylanilines were synthesized with excellent regioselectivities.

Silver-Catalyzed Trifluoromethoxylation of Aziridines

We disclose a silver-catalyzed trifluoromethoxylation of N-tosyl aziridines with trifluoromethyl arylsulfonate. The protocol is characterized by its mild conditions, simple operations, and good chemo- and regioselectivity. In addition, the trifluoromethoxylation of trisubstituted aziridines could construct C-OCF₃ quaternary centers exclusively, which is quite rare. This method unlocks a new catalytic blueprint for accessing β-trifluoromethoxylated amines, which could be important building blocks in synthetic chemistry.

Advances in the Development of Trifluoromethoxylation Reagents

This review provides a short summary of the traditional methods for synthesis of CF3-O-containing compounds, followed by a critical overview of known trifluoromethoxylating reagents, focusing on their preparation, synthetic generality and limitations.

Radical C-H Trifluoromethoxylation of (Hetero)arenes with Bis(trifluoromethyl)peroxide

Trifluoromethoxylated (hetero)arenes are of great interest for several disciplines, especially in agro- and medicinal chemistry. Radical C-H trifluoromethoxylation of (hetero)arenes represents an attractive approach to prepare such compounds, but the high cost and low atom economy of existing . OCF3 radical sources make them unsuitable for the large-scale synthesis of trifluoromethoxylated building blocks. Herein, we introduce bis(trifluoromethyl)peroxide (BTMP, CF3 OOCF3 ) as a practical and efficient trifluoromethoxylating reagent that is easily accessible from inexpensive bulk chemicals. Using either visible light photoredox or TEMPO catalysis, trifluoromethoxylated arenes could be prepared in good yields under mild conditions directly from unactivated aromatics. Moreover, TEMPO catalysis allowed for the one-step synthesis of valuable pyridine derivatives, which have been previously prepared via multi-step approaches.

Trifluoromethyl Nonaflate: A Practical Trifluoromethoxylating Reagent and its Application to the Regio- and Stereoselective Synthesis of Trifluoromethoxylated Alkenes

The trifluoromethoxy group has elicited much interest among drug and agrochemical discovery teams because of its unique properties. We developed trifluoromethyl nonafluorobutanesulfonate (nonaflate), TFNf, an easy-to-handle, bench-stable, reactive, and scalable trifluoromethoxylating reagent. TFNf is easily and safely prepared in a simple process in large scale and the nonaflyl part of TFNf can easily be recovered as nonaflyl fluoride after usage and recycled. The synthetic potency of TFNf was showcased with the underexplored synthesis of various trifluoromethoxylated alkenes, through a high regio- and stereoselective hydro(halo)trifluoromethoxylation of alkyne derivatives such as haloalkynes, alkynyl esters, and alkynyl sulfones. The synthetic merits of TFNf were further underscored with a high-yielding and smooth nucleophilic trifluoromethoxylation of alkyl triflates/bromides and primary/secondary alcohols.