Chemoselective Aerobic Cross-Dehydrogenative Coupling of Terminal Alkynes with Hydrosilanes by a Nanoporous Gold Catalyst.

Aerobic cross-dehydrogenative coupling between terminal alkynes and hydrosilanes occurred in the presence of nanoporous gold catalyst under O2 atmosphere. A variety of alkynylsilanes were synthesized in good-to-high yields and the catalyst was easily recovered and reused many times. Furthermore, the chemoselective direct silyl protection of terminal acetylenes of alkynols over the hydroxyl groups was achieved with this catalytic system.

Asymmetric Allylic Alkylation of ß-Ketoesters with Allylic Alcohols by a Nickel/Diphosphine Catalyst.

Asymmetric allylic alkylation of ß-ketoesters with allylic alcohols catalyzed by [Ni(cod)2]/(S)-H8-BINAP was found to be a superior synthetic protocol for constructing quaternary chiral centers at the α-position of ß-ketoesters. The reaction proceeded in high yield and with high enantioselectivity using various ß-ketoesters and allylic alcohols, without any additional activators. The versatility of this methodology for accessing useful and enantioenriched products was demonstrated.

Catalyst-dependent selectivity in the relay catalytic branching cascade.

The synthesis of small organic molecules as probes for discovering new therapeutic agents has been an important aspect of chemical biology. One of the best ways to access collections of small molecules is to use various techniques in diversity-oriented synthesis (DOS). Recently, a new form of DOS, namely "relay catalytic branching cascades" (RCBCs), has been introduced, wherein a common type of starting material reacts with several scaffold-building agents (SBAs) to obtain structurally diverse molecular scaffolds under the influence of catalysts. Herein, the RCBC reaction of a common type of substrate with SBAs is reported to give two different types of molecular scaffolds and their formation is essentially dependent on the type of catalyst used.

Ligated Pd-Catalyzed Aminations of Aryl/Heteroaryl Halides with Aliphatic Amines under Sustainable Aqueous Micellar Conditions.

Sustainable technology for constructing Pd-catalyzed C-N bonds involving aliphatic amines is reported. A catalytic system that relies on low levels of recyclable precious metal, a known and commercially available ligand, and a recyclable aqueous medium are combined, leading to a newly developed procedure. This new technology can be used in ocean water with equal effectiveness. Applications involving highly challenging reaction partners constituting late-stage functionalization are documented, as is a short but efficient synthesis of the drug naftopidil. Comparisons with existing aminations highlight the many advances being offered.

A sustainable, efficient, and potentially cost-effective approach to the antimalarial drug candidate MMV688533.

A 6-step synthesis of the antimalarial drug candidate MMV688533 is reported. Key transformations carried out under aqueous micellar conditions include two Sonogashira couplings and amide bond formation. Compared with the first-generation manufacturing process reported by Sanofi, the current route features ppm levels of palladium loading, less material input, less organic solvent, and no traditional amide coupling reagents. The overall yield is improved ten-fold, from 6.4% to 67%.

A Streamlined, Green, and Sustainable Synthesis of the Anticancer Agent Erdafitinib.

Erdafitinib, an anticancer drug, was synthesized in a three-step two-pot sequence involving ppm levels of Pd catalyst run under aqueous micellar conditions enabled by a biodegradable surfactant. This process features both pot- and time-economies and eliminates egregious organic solvents and toxic reagents associated with existing routes.

Direct formation of amide/peptide bonds from carboxylic acids: no traditional coupling reagents, 1-pot, and green.

Technology for generating especially important amide and peptide bonds from carboxylic acids and amines that avoids traditional coupling reagents is described. The 1-pot processes developed rely on thioester formation, neat, using a simple dithiocarbamate, and are safe and green, and rely on Nature-inspired thioesters that are then converted to the targeted functionality.

An Efficient and Sustainable Synthesis of the Antimalarial Drug Tafenoquine.

An 11-step, 8-pot synthesis of the antimalarial drug tafenoquine succinate was achieved in 42% overall yield using commercially available starting materials. Compared to the previous manufacturing processes that utilize environmentally egregious organic solvents and toxic reagents, the current route features a far greener (as measured by Sheldon's E Factors) and likely more economically attractive sequence, potentially expanding the availability of this important drug worldwide.

A 1-Pot Synthesis of the SARS-CoV-2 Mpro Inhibitor Nirmatrelvir, the Key Ingredient in Paxlovid.

A newly devised route to the Pfizer drug nirmatrelvir is reported that reduces the overall sequence to a 1-pot process and relies on a commercially available, green coupling reagent, T3P. The overall yield of the targeted material, isolated as its MTBE solvate, is 64%.

Environmentally Responsible and Cost-Effective Synthesis of the Antimalarial Drug Pyronaridine.

Two routes to the antimalarial drug Pyronaridine are described. The first is a linear sequence that includes a two-step, one-pot transformation in an aqueous surfactant medium, leading to an overall yield of 87%. Alternatively, a convergent route utilizes a telescoped three-step sequence involving an initial neat reaction, followed by two steps performed under aqueous micellar catalysis conditions affording Pyronaridine in 95% overall yield. Comparisons to existing literature performed exclusively in organic solvents reveal a 5-fold decrease in environmental impact as measured by E Factors.

A sustainable synthesis of the SARS-CoV-2 Mpro inhibitor nirmatrelvir, the active ingredient in Paxlovid.

Pfizer's drug for the treatment of patients infected with COVID-19, Paxlovid, contains most notably nirmatrelvir, along with ritonavir. Worldwide demand is projected to be in the hundreds of metric tons per year, to be produced by several generic drug manufacturers. Here we show a 7-step, 3-pot synthesis of the antiviral nirmatrelvir, arriving at the targeted drug in 70% overall yield. Critical amide bond-forming steps utilize new green technology that completely avoids traditional peptide coupling reagents, as well as epimerization of stereocenters. Likewise, dehydration of a primary amide to the corresponding nitrile is performed and avoids use of the Burgess reagent and chlorinated solvents. DFT calculations for various conformers of nirmatrelvir predict that two rotamers about the tertiary amide would be present with an unusually high rotational barrier. Direct comparisons with the original literature procedures highlight both the anticipated decrease in cost and environmental footprint associated with this route, potentially expanding the availability of this important drug worldwide.

Pt(IV)-catalyzed hydroamination triggered cyclization: a strategy to fused pyrrolo[1,2-a]quinoxalines, indolo[1,2-a]quinoxalines, and indolo[3,2-c]quinolines.

A PtCl(4)-catalyzed hydroamination-triggered cyclization strategy to access biologically interesting N-containing heterocycles such as pyrrolo[1,2-a]quinoxalines, indolo[1,2-a]quinoxalines, and indolo[3,2-c]quinolines is described. The reaction makes use of aminoaromatics such as 1-(2-aminophenyl)pyrroles, N-(2-aminophenyl)indoles, 2-(2-aminophenyl)indoles, and alkynes having a tethered hydroxyl group. Mechanistically, the reaction is very appealing since it involves multiple catalytic cycles catalyzed by a single metal catalyst PtCl(4). We observed a remarkable enhancement of the rate when reactions were run under microwave-assisted conditions.

Gold- and platinum-catalyzed formal Markownikoff's double hydroamination of alkynes: a rapid access to tetrahydroquinazolinones and angularly-fused analogues thereof.

A highly efficient gold(I)- and platinum(II)-catalyzed process for formal Markownikoff's double hydroamination of alkynes tethered with hydroxyl group has been developed. The method was shown to be applicable to a broad range of 2-aminobenzamides and alkynols leading to the formation of multiply substituted tetrahydroquinazolinones. Interestingly, when Pt(IV)Cl(4) catalyst was employed, cyclic angularly fused compound was obtained.

Platinum-catalyzed formal Markownikoff's hydroamination/hydroarylation cascade of terminal alkynes assisted by tethered hydroxyl groups.

An efficient method for Markownikoff's hydroamination-hydroarylation of alkynols using PtBr(2) as catalyst has been developed. The platinum-catalyzed reactions of alkynols with amino group containing aromatics were achieved in methanol over a reaction time of 6-24 h and temperature ranging from rt to 80 degrees C. This method works well for a variety of alkynols and aromatic amino compounds to give substituted pyrrolo[1,2-a]quinoxalines and indolo[3,2-c]quinolines in good to excellent yields.

Differentiation of o-, m-, and p-fluoro-α-pyrrolidinopropiophenones by Triton B-mediated one-pot reaction.

Positional isomer differentiation is crucial for the analysis of forensic drugs. Presently, it is difficult to distinguish among ortho, meta, and para positional isomers of ring-fluorinated synthetic cathinones, a major class of new psychoactive substances (NPSs), because they exhibit similar chromatographic properties and mass spectral patterns. We describe herein that the ring-fluorinated synthetic cathinone positional isomers, viz. o-, m-, and p-fluoro-α-pyrrolidinopropiophenones (o-, m-, and p-FPPPs), can be discriminated by their benzyltrimethylammonium hydroxide (Triton B)-mediated one-pot reaction with methanol at ambient temperature, followed by chromatographic and mass spectral analyses of the corresponding products. For p-FPPP, fluorine was nucleophilically substituted by the methoxy group to afford p-methoxy-α-pyrrolidinopropiophenone, while o- and m-FPPPs afforded the corresponding FPPP-enamine-pyrrolidine adducts, which allowed the above positional isomers to be unambiguously differentiated by comparing the reaction product chromatograms and mass spectra. The adopted approach, which does not require excess heating or use of metallic catalysts and features the advantages of simplicity and convenience, is expected to contribute toward practical NPS identification.