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.
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 facile and efficient one‐pot synthesis of isoxazol‐3(2H)‐ones has been developed starting from α‐acyl cinnamides and tosyliminophenyliodinane catalyzed by copper(II) acetate [Cu(OAc)2] under very mild conditions involving a tandem aza‐Michael addition and intramolecular cyclization sequence.
A range of N‐methyliminodiacetic acid (MIDA) boronates of commercially available but unstable ortho‐phenolboronic acid derivatives can be readily prepared through simple condensation between the corresponding phenolboronic acids and MIDA in the presence of molecular sieves. The resulting MIDA boronates are bench‐top stable and display a remarkable stability even in DMSO solution at high temperature (>120 °C) compared with their parent boronic acids. Moreover, the utility of the resulting MIDA boronate was successfully demonstrated in a cross‐coupling reaction using the slow‐release protocol to afford the cross‐coupled product in much better yield compared with its parent boronic acid counterpart. In addition, an alternative, but more efficient, synthetic route for difficult‐to‐access ortho‐phenol MIDA boronates has been developed through the MIDA boronate formation of methoxymethyl (MOM) protected ortho‐phenolboronic acid, followed by deprotection of the MOM group with TMSCl under ambient conditions.
A mild and efficient palladium‐catalyzed synthetic method for the C H functionalization of N‐(quinolin‐8‐yl)ferrocenecarboxamide has been developed. Various aryl iodides containing I, NO2, CN, COMe, CO2Et, and NH functionalities and also alkyl iodides underwent the Pd‐catalyzed intermolecular carbon‐carbon bond forming reaction with ferrocenecarboxamide successfully which led to a diverse array of bis(aryl/alkyl)ferrocenecarboxamides in 34–92% yields. Cross‐coupling of the ferrocenyl C H bond with aryl iodides can also be achieved utilizing an economical Ni catalyst. Additionally, selective monoalkylation of ferrocenecarboxamide was studied using sodium bicarbonate as base and dibenzylphosphoric acid as additive under Pd‐catalyzed reaction conditions. Subsequently, removal of the directing group, 8‐aminoquinoline, from bis(aryl)ferrocenecarboxamides led to bis(aryl)ferrocenes bearing versatile methyl ester and carboxaldehyde functional groups.
An efficient palladium(II)‐catalyzed method for the synthesis of alkylated pyridine‐substituted pyrroles has been developed by a one‐pot three component reaction of β‐bromovinyl aldehydes, primary amines and 2‐alkynylpyridines in good yields. The reactions can also provide an efficient route to 2‐picolinoylpyrroles by slightly altering the reaction conditions.
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.
The combination of benzyl bromide, sodium hydroxide and 15‐crown‐5 in tetrahydrofuran is shown to be an efficient method for installing benzyl groups at both the 4‐ and 6‐positions regioselectively directly from peracetylated N‐trichloroacetyl‐protected glucosamine and galactosamine. Application of this benzylation strategy proved to significantly shorten the synthetic route to hyaluronic acid tetra‐ and hexamers.
Practical one‐pot procedures were developed for both Sandmeyer‐type trifluoromethylations and trifluoromethylthiolations. Starting from broadly available (hetero)aromatic amines, various benzotrifluorides were synthesized in high yields via in situ diazotization and copper‐mediated trifluoromethylation using the inexpensive Ruppert–Prakash trifluoromethylating reagent. In the presence of sodium thiocyanate as a sulfur source, aryl trifluoromethyl thioethers are exclusively formed.
The reaction of aldehydes, amines and alcohols usually leads to a series of equilibria from which isolation of one product is difficult to achieve. We have found that this three‐component reaction can be controlled and directed in an exclusive manner toward the formation of the hemiaminal ether. A series of 33 hemiaminal ethers has been obtained in high yields, from different aldehydes, amines and alcohols, under very mild conditions just with molecular sieves as promoter.
Dehydrogenative coupling of primary alcohols with secondary amines to form tertiary amides and dihydrogen (H2) is efficiently catalyzed by bipyridyl‐based ruthenium pincer complexes (0.2–1 mol%) under neutral conditions (in case of the dearomatized complexes), or with added catalytic amount of base. The reaction is sensitive to steric hindrance; in the case of amidation of bulky secondary amines a less sterically hindered complex is more efficient. Selective acylation of primary amines in the presence of secondary amines was also demonstrated.
An asymmetric tandem Michael addition–lactonization between ortho‐nitrovinylphenols and azalactones was investigated for constructing 3,4‐dihydrocoumarin backbones with a quaternary amino acid moiety. Under the catalysis of the chiral squaramide derived from L ‐tert‐leucine, a wide range of substituted (E)‐2‐(2‐nitrovinyl)phenols and azalactones were well tolerated in this tandem reaction to provide the corresponding biologically significant 3,4‐dihydrocoumarin derivatives in excellent yields with high levels of diastereo‐ and enantioselectivity.
We disclose the highly diastereoselective combination of monoamine oxidase‐catalyzed oxidation of meso‐pyrrolidines and aza‐Friedel–Crafts reactions in aqueous buffer to give valuable enantioenriched 2‐substituted pyrrolidines in a formal double C H activation process. A range of secondary as well as tertiary amines were shown to be suitable substrates for the biocatalytic oxidation and subsequent addition of a variety of C‐nucleophiles.
The 8‐aminoquinoline‐directed, nickel(II)‐mediated ortho‐iodination of benzamides using molecular iodine has been developed. The process is highly regioselective and furnishes only monoiodinated products. A broad range of arenes and heteroarenes with diverse functional groups provided monoiodinated products in good to excellent yields.
A new and efficient method for the synthesis of 2‐vinylanilines from the reaction of arylhydrazine hydrochlorides with alkenes and diethyl ketone via a rhodium‐catalyzed C H activation is described. The oxidant‐free olefination reaction involves the in situ generation of an N NCR1R2 moiety as the oxidizing directing group thus providing an easy access to 2‐vinylanilines.
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 synthesis of pyrido[2,1‐a]isoindoles is reported by the rhodium‐catalyzed direct oxidative C H acylation of 2‐aryl pyridines with terminal alkynes. The desired products were obtained in moderate to excellent yields. This is an efficient and clean method to construct C C/C N bonds in one step. In addition, the effective rhodium(III) catalyst was isolated and characterized by X‐ray crystallography.
