The reaction of N‐[2.2]paracyclophanyl‐substituted amides or amines with phenyliodine diacetate (PIDA) and protic nucleophiles affords mixed para‐substituted [2.2]paracyclophane derivatives in moderate to good yields. As protic nucleophiles carboxylic acids and alcohols as well as pyridine hydrobromide can be used. 4‐Hydroxy[2.2]paracyclophane reacts in an analogous manner.
Mono‐ as well as dipropargylic amines were synthesized using α‐amino esters as inexpensive building blocks under a single catalytic system (copper bromide, 100 °C, 4 h, toluene) where the reactant ratio ( 1a / 2a / 3a ) acted as product specific switch. Both secondary (mono) as well as tertiary (di) propargylic amines formed via three‐ and five‐component coupling exhibited wide substrate scope with moderate to good yields and satisfactory diastereoselectivity in a few cases. The practical utility of the method is enhanced by providing a facile access to enantiopure propargylic amines via lipase‐catalyzed resolution along with synthesis of unsymmetrical dipropargylic amines, secondary propargylic amines bearing quaternary carbon centers and imidazolidin‐2‐ones.
In this work an efficient tandem process transforming N‐substituted amidines into secondary amides has been described. The process involves N‐acylurea formation by reaction of the substrate with bis(acyloxy)(phenyl)‐λ3‐iodane followed by isocyanate elimination. The periodinane reagents are obtained from the commercially available phenyliodine(III) diacetate [PhI(OAc)2, (PIDA)] by ligand exchange with carboxylic acids. The N‐substituted amidine substrates are easily synthesized from readily available nitriles. The method is applicable for secondary amide synthesis, based on both aliphatic and (hetero)aromatic amines, including challenging amides consisting of sterically hindered acids and amines. Moreover, the protocol allows one to combine steric bulk with electron deficiency in the target amides (aniline based). Such compounds are difficult to synthesize efficiently based on classical condensation reactions involving carboxylic acids and amines. Overall, the synthetic protocol transforms a nitrile into a secondary amide in both aliphatic and (hetero)aromatic systems.
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.
A straightforward approach for the chemodivergent synthesis of quinolines is described through site‐selective coupling of ortho‐aminoaryl ketones with α‐enolic dithioesters (DTEs) under solvent‐free conditions. The operationally and user‐simple one‐pot methodology is based on the trifunctional nature of DTEs. Both the carbonyl and the thiocarbonyl moiety in α‐enolic dithioesters were employed for the efficient construction of three differently substituted quinolines in a chemoselective manner simply by variation of an easy to handle acid catalyst.
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.
A straightforward and efficient iodine‐promoted ring‐opening/cyclization domino reaction of 1‐cyanocyclopropane 1‐esters for the synthesis of fully substituted 2‐aminofurans is reported. This reaction involves the sequential ring‐opening/intramolecular cyclization reaction of 1‐cyanocyclopropane 1‐esters to give the corresponding 2‐amino‐4,5‐dihydrofurans, which were oxidized with I2 and Et3N in refluxing toluene to give the corresponding 2‐amino‐3‐furancarboxylates.
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.
Efficient Ni‐catalyzed direct cross‐couplings of benzylic alcohol derivatives with arylacetonitriles via C O activation are described. Various α‐benzylated arylacetonitriles including those with functional groups can be prepared under mild reaction conditions.
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 expedient cleavage of the C S bond of dimethyl sulfoxide (DMSO) has been developed for the preparation of substituted pyridines from ketones. In this transformation, the co‐product formic acid was formed from ammonium formate, which acted as an important catalyst for the reaction. Notably, this transformation exhibited a broad substrate scope towards a wide variety of different ketones to give the corresponding substituted pyridines in high yields. Mechanistic studies suggested that dimethyl sulfoxide delivered a methylene fragment, which was subsequently captured in situ to give a pyridine.
The N‐heterocyclic carbene (NHC)‐catalyzed oxidative amidation of aromatic aldehydes with amines in the presence of N‐bromosuccinimide (NBS) as an oxidant has been developed for the synthesis of amides. This amidation strategy is tolerant to both the electronic and the steric nature of the aryl aldehydes employed. The present methodology was extended to chiral amino acid derivatives to generate the corresponding amides in good yields and excellent ee values (>98%).
A practical and efficient synthesis of N‐isobutyronitrile amides has been achieved through the direct condensation of carboxylic acid and azobisisobutyronitrile (AIBN). Carboxylic acids bearing variously substituted phenyl rings and cinnamic or phenylpropiolic acids were employed to furnish both tertiary and secondary isobutyronitrile amides in moderate to high yields. A radical pathway was proposed. The methodology presented here requires no catalysts and additives, and represents the first practical approach to a variety of valuable amides containing the isobutyronitrile structural unit.
A binaphthyl‐supported Pd nanoparticles (Pd‐BNP)‐catalyzed aminocarbonylation of aryl iodides in the presence of carbon monoxide and amines for the synthesis of amides has been developed. This methodology provides an efficient route for the synthesis of a COX‐2 enzyme inhibitor having anti‐inflammatory activity.
Tetrasubstituted propargylic amines are not accessible from ketones under the many catalytic conditions reported for the synthesis of trisubstituted propargylic amines by reacting an aldehyde with an amine and alkyne. The first tandem Markovnikov hydroamination–alkynylation provides direct access to tetrasubstituted propargylic amines from an amine and alkyne via an unusual route involving no carbonyl compounds. A simple copper salt enables both catalytic cycles without ligands, promoters, co‐catalysts, solvents, or by‐products.
A novel copper‐catalyzed oxidative alkylation of α‐amino carbonyl compounds with ethers has been established for the selective synthesis of α‐etherized α‐amino carbonyl compounds. This oxidative alkylation is achieved by dual C(sp3) H bond oxidative cross‐coupling, and its scope is expanded to α‐amino ketones, α‐amino esters and α‐amino amides.
The highly catalytic asymmetric α‐hydroxylation of β‐indanone esters and β‐indanone amides using peroxide as the oxidant was realized with a new C‐2′ substituted Cinchona alkaloid derivatives. The two enantiomers of α‐hydroxy‐β‐indanone esters could be obtained by simply changing the oxidant. This protocol allows a convenient access to the corresponding α‐hydroxy‐β‐indanone esters and α‐hydroxy‐β‐indanone amides with up to 99% yield and 98% ee.
Asymmetric catalytic multistep reactions enable the formation of structurally complex compounds from simple starting materials. Enantioselective Cu‐catalyzed 1,4‐additions of Grignard reagents to Michael acceptors form reactive chiral enolates. We show here that these chiral enolates react in a one‐pot fashion with naked carbenium ions, such as tropylium, 1,3‐benzodithiolium, and dianisylmethylium ions. The corresponding products were obtained in good yields, with enantioselectivities up to 96% ee and high diastereomeric purities.
A method to access α‐thioaryl ketones and α‐thioaryl esters employing copper acetate (hydrate) as catalyst and readily accessible diaryl disulfides and β‐diketones (or β‐keto esters) has been developed. Both alkyl‐ and aryl‐substituted carbonyl compounds can be prepared.
