Photoredox-catalyzed unsymmetrical diamination of alkenes for access to vicinal diamines.

A photoredox-catalyzed unsymmetrical diamination of alkenes by using N-aminopyridinium salts and nitriles as the amination reagents has been developed. Various vicinal diamines were obtained in moderate to excellent yields under mild reaction conditions. Furthermore, this protocol could be applied in the late-stage modification of pharmaceuticals and natural products. Preliminary mechanistic studies suggested that this methodology may undergo a radical pathway followed by a Ritter-type reaction.

Cp*Rh(III)-catalyzed regioselective cyclization of aromatic amides with allenes.

A new Cp*Rh(III)-catalyzed regioselective cyclization reaction of aromatic amides with allenes is reported. The use of allenyl derivatives bearing a directing-group assistant as a reaction promoter was the key to the success of this protocol. In this catalytic system, N-(pivaloyloxy)benzamide substrates react with allenes via Rh-σ-alkenyl intermediates, while N-(pivaloyloxy) indol substrates react via Rh-π-allyl intermediates. These reactions were characterized by mild reaction conditions, a broad substrate scope, and high functional-group compatibility to yield several high-value isoquinolinone and pyrimido[1,6-a]indol-1(2H)-one skeleton-containing compounds. The synthetic applications and primary mechanisms were also investigated.

Rh(III)-Catalyzed Dienylation and Cyclopropylation of 1,2,3-Benzotriazinones with Alkylidenecyclopropanes.

Rh (III)-catalyzed dienylation and cyclopropylation of 1,2,3-benzotriazinones with alkylidenecyclopropanes (ACPs) has been achieved. Different from the previous reports of 1,2,3-benzotriazinones, the triazinone ring remained intact in this C-H bond functionlization reaction. Also, the denitrogenative cyclopropylation could also be realized by changing the reaction temperature. This protocol is featured with high E selectivity, wide substrate scope, and divergent structures of products.

Fluorination of alkylidenecyclopropanes and alkylidenecyclobutanes: divergent synthesis of fluorinated cyclopropanes and cyclobutanes.

A divergent fluorination of alkylidenecyclopropanes (ACPs) and alkylidenecyclobutanes (ACBs) with selectfluor has been achieved. Four different types of products including fluorohydrins, fluoroethers, fluoroesters and fluoroketones could be prepared in moderate to excellent yields. In particular, the cyclopropanes and cyclobutanes were not destroyed during the transformations which involved a radical pathway. The applicability of this method was demonstrated by various transformations of the products.

Divergent Synthesis of Tetrasubstituted Phenols via [3 + 3] Cycloaddition Reaction of Vinyl Sulfoxonnium Ylides with Cyclopropenones.

Two categories of tetrasubstituted phenols were prepared via the cycloaddition reaction of vinyl sulfoxonnium ylides with cyclopropenones in a switchable manner. Copper carbenoid was proposed as the active intermediate in the process of 2,3,4,5-tetrasubstituted phenols formation, while 2,3,5,6-tetrasubstituted phenols were generated via the direct [3 + 3] annulation of vinyl sulfoxonnium ylides with cyclopropenones under metal-free conditions. Further synthetic applications were also demonstrated.

Asymmetric Total Synthesis of Four Stemona Alkaloids.

Asymmetric total syntheses of four Stemona alkaloids were accomplished, and among them, bisdehydrostemoninine A and stemoninine A were synthesized for the first time. Notably, these four alkaloids were divergently synthesized from a common tetracyclic intermediate, which was easily obtained from a known compound. Friedel-Crafts acylation was employed to introduce the key side chain at position C3 of Stemona alkaloids.

Design, synthesis, antitumor activity and ct-DNA binding study of photosensitive drugs based on porphyrin framework.

Photodynamic therapy is a promising novel tumor treatment method. In this study, novel porphyrin-chrysin photosensitizer derivatives were synthesized. Most of the compounds showed antitumor activity against human cervical cancer HeLa cells and human lung cancer A549 cells, among which compound 4c had the best photodynamic therapy effect on HeLa cells and A549 cells, with IC50 values of 6.26 µM and 23.37 µM, respectively. Free-base porphyrin-chrysin derivatives bind to DNA through surface self-stacking, and zinc metalloporphyrin-chrysin derivatives bind to ct-DNA through intercalation. Notably, the tightness of compound binding to ct-DNA was positively correlated with its antitumor activity. What's more, three-dimensional quantitative conformation studies have shown that increasing the positive charge of the porphyrin ring and introducing a strong electron-withdrawing group at the meso position of the porphyrin ring at the para-position of the benzene ring or reducing the space volume of the compound can enhance the antitumor activity.

Lawesson's reagent promoted deoxygenation of azlactones for the syntheses of 2,4-disubstituted thiazoles.

Azlactones and thiazoles are common structural motifs and possess diverse applications. A new method for the efficient and straightforward syntheses of 2,4-disubstituted thiazoles from azlactones has been developed. The reaction proceeded via deoxygenation of azlactones by Lawesson's reagent without metal or external additives. A variety of 2,4-disubstituted thiazoles were synthesized with up to 92% yield. Furthermore, the importance of this methodology was also justified by a gram-scale synthesis.

Tandem reduction and trifluoroethylation of quinolines and quinoxalines with trifluoroacetic acid and trimethylamine borane.

A metal-free tandem reduction and N-trifluoroethylation of quinolines and quinoxalines has been developed. It provided a convenient route to access trifluoroethylated tetrahydroquinolines and tetrahydroquinoxalines. This one-pot method avoids the purification process of the intermediate. Mechanistically, the in situ-generated boryl acetal species reacted with tetrahydroquinolines to generate iminiums followed by reduction to give the target compounds.

Switchable Reductive N-Trifluoroethylation and N-Trifluoroacetylation of Indoles with Trifluoroacetic Acid and Trimethylamine Borane.

The metal-free reductive N-trifluoroethylation and N-trifluoroacetylation of indoles have been developed. Bench stable and inexpensive trimethylamine borane and trifluoroacetic acid (TFA) were utilized as the reductive and fluorinating reagents, respectively. These transformations were switchable on the basis of altering the loading of trimethylamine borane and TFA. Preliminary experiments indicated indoline was the common intermediate in these two transformations.

Oxidative functionalization of alkylidenecyclopropanes and alkylidenecyclobutanes: a versatile platform to access nitrated cyclopropanes and cyclobutanes.

A divergent radical nitration of alkylidenecyclopropanes (ACPs) and alkylidenecyclobutanes (ACBs) with Fe(NO3)3·9H2O or AgNO2 has been achieved, affording three categories of products including ß-nitro alcohol, α-nitro ketone and nitro nitratosation products with yields up to 90%. Particularly, the cyclopropyl and cyclobutyl rings were conserved in the products. The applicability of this method was demonstrated by the scale-up experiment and reduction of the nitro into an amino group. Preliminary mechanistic studies suggested that the nitro radical was involved in the reaction process.

Metal-free regioselective nitration of quinoxalin-2(1H)-ones with tert-butyl nitrite.

A metal-free coupling of quinoxalin-2(1H)-ones with tert-butyl nitrite has been developed. Distinctly from the previous functionalization of quinoxalin-2(1H)-ones, this nitration reaction took place selectively at the C7 or C5 position of the phenyl ring, affording a series of 7-nitro and 5-nitro quinoxalin-2(1H)-ones in moderate to good yields. Preliminary mechanistic studies revealed that the reaction may involve a radical process.

Mild Synthesis of 3,4-Dihydroisoquinolin-1(2H)-ones via Rh(III)-Catalyzed Tandem C-H-Allylation/N-Alkylation Annulation with 2-Methylidenetrimethylene Carbonate.

A tandem rhodium(III)-catalyzed system was established to access 3,4-dihydroisoquinolin-1(2H)-one by coupling of N-methoxy-3-methylbenzamide with 2-methylidenetrimethylene carbonate. This one-pot synthesis protocol processed smoothly under mild reaction conditions. Moreover, a total of 28 examples, broad substrate scope, and high functional-group compatibility were observed. Preliminary mechanism studies were also conducted and demonstrated that the rhodium(III) catalyst played a vital role in the C-H-allylation and N-alkylation cyclization process.

Access to Branched Allylarenes via Rhodium(III)-Catalyzed C-H Allylation of (Hetero)arenes with 2-Methylidenetrimethylene Carbonate.

A rhodium(III)-catalyzed C-H allylation of (hetero)arenes by using 2-methylidenetrimethylene carbonate as an efficient allylic source has been developed for the first time. Five different directing groups including oxime, N-nitroso, purine, pyridine, and pyrimidine were compatible, delivering various branched allylarenes bearing an allylic hydroxyl group in moderate to excellent yields.

Halohydroxylation of alkenyl MIDA boronates: switchable stereoselectivity induced by B(MIDA) substituent.

The synthesis of α-boryl halohydrins via difunctionalization of alkenyl MIDA boronates has been reported. Intriguing stereoselectivity was found with different halogen sources, which arises from the special stabilizing effect of the B(MIDA) moiety. The transformation provided cis addition products using Cl+ or Br+ as the halogen source, while trans addition products were obtained when I+ was employed.

Diversity-Oriented Synthesis of α-Functionalized Acylborons and Borylated Heteroarenes by Nucleophilic Ring Opening of α-Chloroepoxyboronates.

The ring-opening reactions of N-methyliminodiacetyl (MIDA) α-chloroepoxyboronates with different nucleophiles allow the modular synthesis of a diverse array of organoboronates. These include seven types of α-functionalized acylboronates and seven types of borylated heteroarenes, some of which are difficult-to-access products using alternative methods. The common synthons, α-chloroepoxyboronates, could be viably synthesized by a two-step procedure from the corresponding alkenyl MIDA boronates. Mild reaction conditions, good functional-group tolerance, and generally good efficiency were observed. The utility of the products was also demonstrated.

Synthesis of novel genistein amino acid derivatives and investigation on their interactions with bovine serum albumin by spectroscopy and molecular docking.

Genistein amino acid derivatives 4a-4d were synthesized and evaluated for their cytotoxic activities against MCF-7, Hela, MGC-803 and HCT-116 cell lines by MTT assays in vitro. The results revealed that compounds 4a-4d showed better activity than the parent compound genistein. Particularly, compound 4b displayed the most significant anticancer activity against MGC-803 with an IC50 value of 12.08 µM. In addition, the mechanisms of interaction between genistein, compounds 4a-4d and BSA were investigated via multi-spectroscopic techniques such as ultraviolet (UV) spectroscopy, fluorescence, circular dichroism (CD), and molecular docking under physiological conditions. The results suggested that endogenous fluorescence of BSA could be quenched by genistein and compounds 4a-4dvia forming BSA-compound complex, which meant a static quenching mechanism was involved. The negative values of enthalpy (ΔH) and entropy (ΔS) indicated that interactions between BSA and the ligands were spontaneous, and hydrogen bonding and van der Waals interactions were involved in the BSA-compound complexion formation. The UV, synchronous and 3D fluorescence results revealed that the micro-environment of tryptophan and conformation of BSA were changed after binding to ligands. CD analysis demonstrated the variation in the secondary structure and that the α-helix content of BSA decreased. Eventually, molecular docking was executed to forecast the binding forces and binding sites between BSA and compounds 4a-4d.

Stereoselective Direct Chlorination of Alkenyl MIDA Boronates: Divergent Synthesis of E and Z α-Chloroalkenyl Boronates.

The individual molecules of α-chloroalkenyl boronates include both an electrophilic C-Cl bond and a nucleophilic C-B bond, which makes them intriguing organic synthons. Reported herein is a stereodivergent synthesis of both E and Z α-chloroalkenyl N-methyliminodiacetyl (MIDA) boronates through the direct chlorination of alkenyl MIDA boronates using tBuOCl and PhSeCl reagents, respectively. Both reaction processes are stereospecific and the use of sp3 -B MIDA boronate is the key contributor to the reactivity. The synthetic value of the boronate products was also demonstrated.

Direct Assembly of Prenylated Heteroarenes through a Cascade Minisci Reaction/Dehydration Sequence.

The prenyl group is an important component in bioactive compounds. Herein, we report the assembly of prenylated heteroarenes through a cascade Minisci reaction and acid-promoted dehydration sequence. The use of potassium (3-hydroxy-3-methylbut-1-yl)trifluoroborate as a new coupling reagent allows the direct introduction of prenyl and 3-hydroxy-3-methylbutyl groups to a wide variety of electron-deficient heteroarenes. Synthetic application is also demonstrated.

Oxidative Difunctionalization of Alkenyl MIDA Boronates: A Versatile Platform for Halogenated and Trifluoromethylated α-Boryl Ketones.

The synthesis of halogenated and trifluoromethylated α-boryl ketones via a one-pot oxidative difunctionalization of alkenyl MIDA boronates is reported. These novel densely functionalized organoborons bearing synthetically and functionally valuable carbonyl, halogen/CF3 and boronate moieties within the same molecule are synthetically challenging for the chemist, but have great synthetic potential, as demonstrated by their applications in a straightforward synthesis of borylated furans. The generality of this reaction was extensively investigated. This reaction is attractive since the starting materials, alkenyl MIDA boronates, are easily accessible.