This paper describes the aerobic oxidation of styrenes catalyzed by iron(III) chloride (FeCl3) to form β‐keto‐N‐alkoxyphthalimides in fair to good yields. This oxidative process employs mild conditions with green and atom efficient dioxygen (O2) as the oxidant.
Boron trifluoride nitrile complexes promote oxidative [2+2+1] annulations of alkynes, nitriles and N‐atoms from iminoiodanes to give the corresponding 2,4‐disubstituted and 2,4,5‐trisubstituted N‐tosylimidazoles in moderate to good yields with high regioselectivities.
A novel and efficient oxidative annulation of 2‐aminobenzamides with nitromethane has been developed for the chemoselective synthesis of N‐substituted 1,2,3‐benzotriazine‐4(3H)‐ones in moderate to excellent yields under transition metal‐free conditions. Two N N bonds were constructed in one pot via C N cleavage of nitromethane, which was selectively employed as the nitrogen synthon. The preliminary mechanistic studies revealed that this protocol proceeded under hypoiodite catalysis generated in situ.
A new one‐pot palladium‐catalyzed process between N‐tosylhydrazones, N‐(dihalophenyl)‐imidates, and amines was designed. This reaction involves Barluenga cross‐coupling and N‐arylation followed by cyclization to produce functionalized benzimidazoles. During this transformation, one C C bond and two C N bonds were created by a single palladium‐catalyzed reaction. Depending on the starting materials, a library of 5‐(1‐arylvinyl)‐1H‐benzimidazoles was synthesized. Among several arylvinylbenzimidazole derivatives evaluated, one compound exhibits excellent antiproliferative activity in the nanomolar concentration range against human colon carcinoma cell lines (HCT‐116) and human lung adenocarcinoma epithelial cell lines (A549).
We have developed a palladium(0)‐catalyzed tandem process which involves the cross‐coupling reaction of N‐tosylhydrazones with dibromide compounds followed by a sequence of intramolecular 5‐exo‐trig, 3‐exo‐trig cyclization, ring opening, and β‐hydride elimination to produce 6‐endo‐trig cyclized products. The strategy was successfully applied for the regioselective synthesis of substituted benzo[b]naphtho[2,1‐d]thiophenes, naphtho[1,2‐b]benzofurans, and benzo[a]carbazoles in moderate to excellent yields.
A divergent synthesis of cyclitol derivatives has been developed utilizing an N‐heterocyclic carbene‐catalyzed benzoin‐type cyclization of C2‐symmetrical dialdoses. The resulting inososes are versatile intermediates, which are readily converted into not only inositols but also amino‐, deoxy‐, O‐methyl‐ and C‐methyl‐inositols.
A synthetic strategy has been developed for the synthesis of 2‐dialkylaminoquinolines from easily available quinoline N‐oxides, tertiary amines, diisopropyl H‐phosphonate and carbon tetrachloride (CCl4) in one pot under metal‐free conditions at room temperature.
Readily available cyclobutanols having a butyne‐1,4‐diol moiety underwent a sequential regioselective Meyer–Schuster rearrangement and 1,2‐shift, furnishing α‐hydroxy‐α‐vinylcyclopentanones. The reaction mechanism is consistent with the formation of an allenol intermediate that racemizes under the reaction conditions. Subsequent activation of the allenol leads to an enantio‐ and diastereoselective route to this scaffold.
Polyfunctional molecules, 1,5‐enynes, have been achieved via a palladium(0)‐catalyzed domino coupling reaction of (Z)‐β‐bromostyrenes with norbornenes in the presence of cesium carbonate and N,N‐dimethylformamide. The process involves a double Heck‐type procedure, two‐fold C(sp2) H activation and formation of two carbon‐carbon bonds. There are possibilities of diversified transformation for the domino coupling of (Z)‐β‐bromostyrenes with norbornenes, the procedure is successfully driven to 1,5‐enynes via accurate adjustment of the reaction conditions.
The asymmetric aldol reaction of 3‐acetyl‐2H‐chromen‐2‐ones and isatins has been realized by using a bifunctional quinidine‐derived urea as the catalyst. The corresponding 3‐hydroxyoxindole derivatives containing a 2H‐chromen‐2‐one moiety were obtained in good yields and high enantioselectivities. When (Z)‐ethyl 2‐benzylideneacetoacetate was used as the substrate, a mixture of two diastereomers (both Z and E) was obtained due to isomerization of the double bond under the reaction conditions.
The paper describes the oxidative Heck arylation of various allylic amines using arylboronic acids for the preparation of tetrasubstituted alkenes. As oxidant the commercially available 2,2,6,6‐tetramethylpiperidine‐N‐oxyl (TEMPO) is used and coupling reactions occur under very mild conditions at room temperature. The densely substituted alkenes are formed in good to excellent yields with complete control of the diastereoselectivity. Substrate scope with respect to the allylic amine and the arylboronic acid is investigated.
Aerobic oxidation using a combination of copper salts and 2,2,6,6‐tetramethylpiperidine N‐oxyl (TEMPO) represent useful tools for organic synthesis and several closely related catalyst systems have been reported. To gain further insights, these catalytic systems were evaluated in a gas–liquid segmented flow device. The improvement of oxygen mass transfer has a significant influence on the turnover‐limiting step. Hence, an improved catalytic system using copper(II) as copper source was implemented in a microreactor for the safe and efficient oxidation of primary alcohol.
A new palladium‐catalyzed route to 3‐hydroxy‐4‐arylcyclopentanones and 4‐arylcyclopentenones in a diastereo‐ and enantioselective manner by a Heck–Matsuda desymmetrization was achieved from the commercially available meso cis‐4‐cyclopentene‐1,3‐diol. This method is highly practical, mild, high yielding and is carried out under “open vessel” conditions. Protected and unprotected substrates provide distinct products bearing considerable value as synthetic scaffolds for the synthesis of natural and unnatural bioactive compounds containing a five‐membered ring.
A novel and convenient palladium‐catalyzed cross‐coupling reaction of H‐phosphonate diesters with sodium arylsulfinates was developed via desulfitation in the presence of silver carbonate and tetra‐butylammonium chloride. This method is highly efficient and provides a rapid access to a broad spectrum of arylphosphonate diesters in good to excellent yields.
A synthetic method for the construction of fully substituted enantioenriched 1,4‐dihydroquinolines using an organocatalytic aza‐Michael/Michael cascade reaction has been developed. The asymmetric reaction of 2‐(tosylamino)phenyl α,β‐unsaturated ketones with alkynyl aldehydes, promoted by diphenylprolinol O‐TMS ether as an organocatalyst, generated chiral 1,4‐dihydroquinolines in good to high yields with excellent enantioselectivities (up to 97 % ee).
The palladium‐catalyzed acylation of 2‐aryl‐1,2,3‐triazoles with aldehydes via C H bond activation is described. A wide variety of products was isolated in good to excellent yields. This finding provides a new and useful strategy for the synthesis of aromatic ketones.
