A novel method for the synthesis of 3‐iodoquinolines was developed by copper‐catalyzed tandem annulation from diaryliodoniums, nitriles, and 1‐iodoalkynes. It is a method that is characterized by the most convenient operation and wide molecular diversity.
A chemoselective reduction of α‐keto amides to biologically important α‐hydroxy amides (mandelamides) by polymethylhydrosiloxane (PMHS) using 5 mol% potassium phosphate (K3PO4) as catalyst has been developed. This transition metal‐free protocol discloses excellent chemoselectivity for the ketone reduction of α‐keto amides in the presence of other reducible functionalities like ketone, nitro, halides, nitrile and amide. Also, the chemoselectively reduced α‐hydroxy amide has been derivatized to isocyanide‐free Passerini adducts. The N‐alkyl‐α‐hydroxy amides have been successfully converted to 3‐phenyloxindole derivatives by treatment with methanesulfonyl cholride and triethylamine.
A metal‐free vinylic carbon‐hydrogen bond thiolation has been developed. Under the catalysis of iodine (10 mol%), the cyclization of α‐alkenoyl ketene dithioacetals afforded a broad range of polyfunctionalized 2‐methylene‐3‐thiophenones in good selectivity with moderate to excellent yields via tandem iodocyclization and dehydroiodination. The synthetic strategy can also be extended to the cyclization of ortho‐methylthiophenyl vinyl ketones leading to 2‐methylene‐3‐benzothiophenones.
A direct enantioselective reaction of cyclopent‐2‐enone‐derived Morita–Baylis–Hillman alcohols with 4‐hydroxycoumarins has been developed under the catalysis of a chiral primary amine derived from cinchonine in combination with a Brønsted acid. The reaction provides pyranocoumarin products with three vicinal chiral carbon centers in highly regio‐, diastereo‐ and enantioselectivities through a tandem allylic alkylation/intramolecular oxa‐Michael addition.
A divergent approach to generate either 1‐hydroxymethylindenes (which could then be converted to benzofulvenes through a dehydration reaction) or naphthalenes by the rearrangement of cycloprop[2,3]inden‐1‐ols is reported. The effect of the cyclopropyl ring substitution pattern on ring‐opening/expansion rearrangements of the substrates was systemically studied.
We report here that the silver triflate‐catalyzed cyclization of 2‐amino‐6‐propargylamineazines affords new and highly functionalized iminoimidazoazines. We have investigated the scope and limitations of the present methodology, and some aspects of the reactivity of the resulting iminoimidazopyridines have been explored, and a DFT‐based mechanistic analysis of the silver triflate‐catalyzed cyclization has been undertaken.
The first enantioselective Friedel–Crafts alkylation of indoles and pyrroles with 3‐hydroxy‐3‐indolyloxindoles to access two novel types of 3,3‐diaryloxindoles catalyzed by chiral imidodiphosphoric acids has been reported. A range of quaternary carbon centered 3,3‐diaryloxindoles were synthesized in high yield (up to >99%) with excellent enantioselectivity (up to 98% ee) at low catalyst loadings (as low as 0.5 mol%). The Friedel–Crafts reaction between indoles and 3‐hydroxy‐3‐indolyloxindoles is amenable to gram scale syntheses.
Imino‐/enaminophosphonates derived from amines and diethyl phenacyl phosphonates undergo oxidative cyclization via C H bond activation catalyzed by palladium chloride to provide a convenient route for the synthesis of substituted indol‐3‐yl and pyrrol‐3‐yl phosphonates.
A simple and efficient ligand‐free nickel‐based catalytic system has been developed for the 1,4‐addition of arylboronic acids to α,β‐unsaturated carbonyl compounds. With catalyst loadings of 1–2 mol%, a series of 1,4‐adducts from chalcones and cinnamates was obtained in moderate to excellent yields within 5–30 min under a nitrogen atmosphere and microwave irradiation. The 1,4‐addition of arylboronic acids to acrylates is less efficient.
The selective copper‐catalyzed borylation of silylalkynes in the presence of a diboron reagent and methanol produced a variety of (Z)‐β‐(borylvinyl)silanes. The appropriate use of a selective ligand for copper allows the chemo‐, regio‐, and stereoselective monoborylation of silylalkynes. The β‐regioselectivity of an N‐heterocyclic carbene (NHC)‐copper catalyst was investigated by DFT calculations.
A novel methodology has been developed for the synthesis of chiral phosphoryl‐1,4‐dihydropyridazine derivatives based on an asymmetric allylic alkylation/intramolecular 1,3‐dipolar cycloaddition/rearrangement reaction sequence, various chiral 3‐phosphoryl‐4‐aryl‐1,4‐dihydropyridazine‐5‐carboxylates were achieved in high yields with high enantioselectivities. Moreover, chiral 4,5‐dihydropyridazinone derivatives were also facilely furnished by the reduction of the allylic alkylation products of Morita–Baylis–Hillman carbonates and α‐diazophosphonates.
A rhodium(III)‐catalyzed selective olefination of picolinamide derivatives has been developed. The reaction shows high regioselectivity, low catalyst loading (0.5 mol%), high yield and good functional group tolerance, providing a convenient strategy for the synthesis of 3‐alkenylpicolinamides.
α‐Substituted β‐acetyl amides could undergo C C bond cleavage to form α‐keto amides when treated with copper(II) chloride (CuCl2) and boron trifluoride diethyl etherate (BF3⋅OEt2) under an oxygen atmosphere. The yield can be increased by the addition of tert‐butyl hydroperoxide which alone can also effect the reaction. The reaction provides a new protocol for the synthesis of α‐keto amides.
α‐Allenols were catalytically transformed into dihydrofurans in the presence of platinum dichloride. Notably, using platinum dichloride along with silver triflate as the catalytic system, α,β‐unsaturated ketones were obtained. Therefore, the role of the silver salt may not just consist in the activation of the platinum precatalyst.
