Organic & Biomolecular Chemistry

Herein the first example of conversion of alcohols into carboxylic acids by use of the Dess-Martin Periodinane (DMP), which is otherwise routinely employed for the conversion to aldehydes, is reported. This methodology will have significant potential utility in the synthesis of cytidine analogues and other related biologically important molecules.

We report here a simple and atom economic cycloisomerization reaction of indole-tethered alkynols for constructing diverse carbazoles using Cu(OTf)2 /HFIP as the excellent promoter system. The reaction proceeds through a one-pot, domino process of spiro cyclization and 1,2-migration followed by aromatization to deliver carbazoles.

The reaction of 3-halo-5,6-dihydro-4 H -1,2-oxazine N -oxides with arynes was studied. Arynes were generated from o -silylaryl triflates and underwent consecutive [3 + 2]-cycloaddition/[4 + 2]-cycloreversion with N -oxides leading to substituted 3-vinyl-benzisoxazoles in high yields. In the presented sequence, 1,2-oxazine N -oxides act as surrogates of rarely employed unsaturated nitrile oxides. A broad substrate scope was demonstrated. The influence of the substitution pattern of an aryne on the reaction outcome was determined...

Herein, we report that prism[6]arenes (PrS[6]R) can form charge-transfer (CT) inclusion complexes with tropylium tetrakis[3,5-bis(trifluoromethyl)-phenyl]borate (G) in chloroform solution with an obvious CT band at 560 nm. Moreover, the CT complex PrS[6]Et⊃G showed Cl- /Ag+ responsiveness which can be easily monitored by the naked eye.

We have developed a nickel-catalysed regio- and stereoselective hydrocyanation of alkynoates that gives syn -β-cyanoalkenes. DFT calculations suggest that a favored transition state promotes Cα-H bond formation for determining regio- and stereoselectivity of the products.

This report covers boron tribromide (BBr3 ) mediated dearomative spirocyclization of biaryl ynones. The direct synthesis of spiro[5.5]dienones with a tri-substituted double bond is described for the first time in this paper. The scope of the reaction is broad and the spirocyclic products were obtained in moderate to good yields.

Photochromism through excited-state intermolecular proton transfer (ESInterPT) processes based on keto-enol tautomerization was found in phenazine-2,3-diol PD1 and its monoalkoxy derivative PD2 in a glassy matrix at 77 K: the colorless solutions of enol forms PD1-E and PD2-E at 298 K transformed into orange-colored solutions of keto forms PD1-K and PD2-K upon photoirradiation ( λ = 385 nm) at 77 K. Furthermore, this report is the first to achieve the single-crystal X-ray structural analyses of phenazine-2,3-diol PD1 and its monoalkoxy derivative PD2, since the report on the synthesis of PD1 70 years ago...

An efficient electrochemical nickel-catalyzed cross-coupling reaction has been reported here for the synthesis of S -glycosides from preactivated phenols and ketones under mild conditions. Various glycosyl thiols, including unprotected sugar, and a diverse range of aryl/alkenyl triflates, including some complex biorelevant phenols and ketones, were well tolerated in this method.

In this study, we investigated the photo-catalytic mechanisms for the construction of C-O bonds from arenes (benzene, 2',6'-dimethyl-[1,1'-biphenyl]-2-carboxylic acid, or 2,4-dichloro-1-fluorobenzene), catalyzed by 2,3-dichloro-5,6-dicyano- p -benzoquinone (DDQ). All the structures for the Gibbs free surfaces were calculated at the M06-2X-D3/ma-def2-SVP level in the SMD solvent model. Also, TDDFT calculations of DDQ were performed at the PBE1PBE-D3/ma-def2-SVP level in the SMD solvent model. The computational results indicated that DDQ, serving as a photo-catalyst, would be excited under visible light of 450 nm, aligning well with experimental observations as reflected in the UV-vis spectrum...

Naturally occurring sesquiterpenes having humulane frameworks are structurally intriguing and possess significant biological profiles. Asymmetric synthesis of the alashanoids B, C, E, and F and 2,9-humuladien-6-ol-8-one is achieved for the first time through a linear synthetic strategy. Intramolecular late-stage Nozaki-Hiyama-Kishi (NHK) coupling is employed to access the eleven-membered macrocyclic core present in the target molecules. The NHK precursors are accessed using the Evans and non-Evans syn and anti -aldol reaction as a key transformation...

Herein, we describe an efficient method for the synthesis of alkenylphosphine oxides via a Tf2 O promoted addition-elimination process. Various diarylphosphine oxides and alkylarylphosphine oxides react with ketones smoothly and produce alkenylphosphine oxides in moderate to excellent yields with abundant functional group compatibility. In addition, several transformations and applications of the product also demonstrate the potential value of the methodology.

The first and concise syntheses of the anticancer agent diplofuranone A and the fatty acid-derived metabolite diapolic acid A have been demonstrated using easily accessible and commercially available starting materials. The key feature of these syntheses is the efficient diversification of highly stereo- and chemoselectively constructed ( E , E )-1,6-dioxo-2,4-dienes using ruthenium catalytic conditions, which enabled straightforward access to diversely substituted bioactive molecules.

Chemical tools and principles have become central to biological and medical research/applications by leveraging a range of classical organic chemistry reactions. Friedel-Crafts alkylation and acylation are arguably some of the most well-known and used synthetic methods for the preparation of small molecules but their use in biological and medical fields is relatively less frequent than the other reactions, possibly owing to the notion of their plausible incompatibility with biological systems. This review demonstrates advances in Friedel-Crafts alkylation and acylation reactions in a variety of biomolecular chemistry fields...

Dimethyl sulfoxide (DMSO)-promoted catalyst-free oxidative C-N coupling and C-O coupling under oxidant-free conditions are outlined. This protocol is operationally simple and leads to various functionalized substituted imidazoles or oxazoles in good yields. To date, a very limited number of oxidation protocols have been established, where DMSO acts solely as a catalyst or an oxidant or both. In this report, DMSO is not only used as a C-N/C-O coupling agent but is also used as the oxidant required for these oxidative transformations...

Asp-based lactam cyclic peptides are considered promising drug candidates. However, using Fmoc solid-phase peptide synthesis (Fmoc-SPPS) for these peptides also causes aspartimide formation, resulting in low yields or even failure to obtain the target peptides. Here, we developed a diaminodiacid containing an amide bond as a β-carboxyl-protecting group for Asp to avoid aspartimide formation. The practicality of this diaminodiacid has been illustrated by the synthesis of lactam cyclic peptide cyclo[Lys9,Asp13] KIIIA7-14 and 1Y...

Combined UV-vis and quantum chemical studies of the structural flexibility and tautomerism of 6-R-3-hydroxy-2-pyrazine carboxamides in solutions revealed that their keto-enol transformations are accompanied by the deprotonation of enol tautomers and the formation of the corresponding anionic species. Both the solvent and the 6-R substituent strongly influence the relative abundance of the above forms in solutions. Anions are not formed in 1,2-dichloroethane (DCE), but the probability of deprotonation in neutral water and N , N -dimethylformamide (DMF) increases in the order R = H < F < NO2 ...

Herein, we report a visible light-enabled radical trihalomethylation/cyano-migration/carbonylation cascade reaction of 2-hydroxy-2-hex-5-enenitrile with CX3 SO2 Cl as the CX3 -source (X = F, Cl) to obtain 5-oxo-2-(2,2,2-trihaloethyl)pentanenitrile compounds in the absence of a photocatalyst, transition metal and base. This reaction system is also effective to convert (benzo[ d ]thiazol-2-yl)-pent-4-enol to the corresponding 4-(benzo[ d ]thiazol-2-yl)-6,6,6-trihalo-hexanone products. These reactions occur under mild conditions, tolerate a wide range of functional groups, and provide alternative approaches for the 1,2-bifunctionalization reaction of unactivated olefins...

Synthesis of alk-2-ynl-Weinreb amides via Pd-catalyzed oxidative carbonylation of terminal alkynes and N , O -dimethylhydroxylamine hydrochloride at room temperature under low CO/O2 pressure is reported for the first time. This protocol offers tolerance of various functional groups under mild reaction conditions. The protocol incorporates aromatic- and aliphatic-substituted alkynes through a one-step oxidative carbonylative route toward desired alkynyl Weinreb amides, which are of considerable importance as valuable synthetic building blocks...

Post-synthetic conversion of the trifluoromethyl group to a heteroaryl group at the C5 position of the pyrimidine base in DNA oligonucleotides was achieved. Specifically, the oligonucleotides containing 5-trifluoromethylpyrimidine bases were treated with o -phenylenediamines and o -aminothiophenols as nucleophiles to afford the corresponding 5-(benzimidazol-2-yl)- and 5-(benzothiazol-2-yl)-pyrimidine-modified bases. Furthermore, evaluation of the fluorescence properties of the obtained oligonucleotides revealed that among them the oligonucleotide containing 5-(5-methylbenzimidazol-2-yl)cytosine exhibited the highest fluorescence intensity...

Thiols and thioesters play crucial roles in pharmaceuticals, biology, and material science as essential organosulfur compounds. Leveraging readily available and cost-effective inert alkanes through direct thioetherification holds promise for yielding high-value-added products. Herein, we present a photoinduced strategy for sulfur-containing modification of inert alkanes utilizing decatungstate as hydrogen atom transfer reagent, offering a straightforward and practical approach for synthesizing thioethers and thioesters...