FeCl3-catalyzed Ritter reaction. Synthesis of amides

A safe and inexpensive synthesis of amides, from benzylic alcohols and nitriles and from t-butyl acetate and nitriles, using a Ritter reaction catalyzed by FeCl₃·6H₂O is described.     

Microwave assisted,Ca(II)-catalyzed Ritter reaction for the green synthesis of amides

An efficient solvent-free synthesis of amides by Ca(II) catalyzed Ritter reaction has been reported under microwave irradiation. This green protocol tolerates the substrate diversity and delivers the high yielding amides with minimal loading of inexpensive and more abundant Ca(II) catalyst.     

Organocatalytic synthesis of amides from nitriles via the Ritter reaction

A simple, inexpensive, environmentally friendly, and efficient route for the synthesis of a wide variety of amides in high yields via the Ritter reaction of alcohols with nitriles has been demonstrated. Pentafluorophenyl ammonium triflate (PFPAT) is used as an organocatalyst and is air-stable, cost-effective, easy to handle, and easily removed from the reaction mixtures.     

Facile preparation of difluoromethyl- and monofluoromethyl-containing amides via Ritter reaction

Both secondary and tertiary difluoromethylated carbinols were found to readily react with acetonitrile under the catalysis of concentrated sulfuric acid to give the corresponding difluoromethylated acetamides in good yields, which is remarkably more efficient than the previously reported Ritter reactions with corresponding trifluoromethylated carbinols. Similarly, monofluoromethylated and (benzenesulfonyl)difluoromethylated carbinols have shown good reactivity in the Ritter reactions. Since the acetamides can be mildly deacetylated to give amines, the present methodology provides a convenient way for the synthesis of both difluoromethyl- and monofluoromethyl-containing amines starting from simple carbonyl compounds.     

Iodine-catalyzed one-pot synthesis of amides from nitriles via Ritter reaction

Ritter reactions of alcohols and tert-butyl acetate with various nitriles were performed using iodine as a mild and effective catalyst under heating conditions to afford the corresponding amides in good to excellent yields.     

Intervention of phenonium ion in Ritter reactions

The transformation of phenylethyl chloride to 3,4-dihydroisoquinolines is shown to proceed via phenonium ion. The evidence comes from a study of dideuterated analogue 4, and the monomethylated and dimethylated compounds 2 and 3.     

Synthesis of amides using the Ritter reaction with bismuth triflate catalysis

N-tert-Alkyl and aryl amides were obtained by a Ritter reaction of various nitriles with tertiary alcohols in the presence of a catalytic amount of bismuth triflate.     

Highly efficient synthesis of amides via Ritter chemistry with ionic liquids

The utility of Brønsted-acidic imidazolium ionic liquid [BMIM(SO₃H)][OTf] as catalyst for the high yield synthesis of a wide variety of amides under mild conditions via the Ritter reaction of alcohols with nitriles has been demonstrated. As alternative methods for the carbocation generation step, NOPF₆ immobilized in [BMIM][PF₆] ionic liquid was used in the Ritter reaction of bromides with nitriles and for the synthesis of adamantyl amides from adamantane and nitriles.     

Nafion-catalyzed microwave-assisted Ritter reaction: an atom-economic solvent-free synthesis of amides

An atom-economic solvent-free synthesis of amides by the Ritter reaction of alcohols and nitriles under microwave irradiation is reported. This green protocol is catalyzed by solid-supported Nafion^®NR50 with improved efficiency and reduced waste production.     

Ritter reactions. X. Structure of a new multicyclic amide-benzene inclusion compound

5H-Dibenzo[a, d]cyclohepten-5-ol1 can undergo Ritter reaction with acetonitrile and sulfuric acid to afford either the acetamide derivative2 or the multicyclic amide3 depending on the conditions used. The X-ray structure of the inclusion compound of3 with benzene is reported here and analysed in structural terms. This material [(C₁₉H₁₈N₂O)–(C₆H₆),Cc,a=10.694(5),b=22.843(5),c=9.901(4) Å,=124.02(2)°,Z=4,R=0.054] has molecules of3 linked by –N–HO=C intermolecular hydrogen bonds to form parallel chains alongc. Additional inter-host stabilisation is achieved by face-face interactions involving one of the two benzo rings of3. A hydrogen atom of the other host benzo group participates in an edge-face interaction with the benzene guest molecule to produce the inclusion compound. Benzenebenzene inter-guest interactions provide a further, but minor, contribution to the net stability of the structure. Supplementary Data relating to this article are deposited with the British Library as supplementary publication No. SUP 82189 (10 pages).     

Synthesis of N-substituted amides by the Ritter reaction with heteropoly acids as catalysts

Reactions of a number of nitriles with camphene in the presence of the heteropoly acids H₃PW₁₂O₄₀, H₇PMo₁₂O₄₂, and H₄SiW₁₂O₄₀ as catalysts were studied. In all cases, N-substituted amides were obtained in sufficiently high yields. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 374–376, February, 2006.     

Ritter reactions. VI. Crystal structure of a new multicyclic hydroxy amide clathrate

The compound 9-benzamido-6,7,8,9,10,11-hexahydro-5,9:7,11-dimethano-5H-benzocyclononen-7-ol,3, has been prepared, and found to crystallise as inclusion complexes ( ₂ ·G where the guest G is ethyl acetate or carbon tetrachloride. The host molecule contains a benzo group as part of a rigid polycyclic framework, on which there are hydroxy and benzamido substituents. The crystal structure of the complex with CCl₄ contains the host molecules hydrogen-bonded in layers, with the CCl₄ molecules trapped between the layers. Two types of host-host hydrogen bonds, OH to amide carbonyl O, and amide NH to hydroxyl O, maintain the host layers. The benzo groups protrude normal to these host layers, and six such groups provide the closest surroundings of the CCl₄, which is constrained to two disordered orientations at the one location. This is a layer clathrate structure. Supplementary Data relating to this article are deposited with the British Library as supplementary publication No. SUP 82110 (13 pages).     

Reductive ring opening reactions of diphenyldihydrofullerenylpyrroles

The reductive ring opening reaction conditions for the simple [60]fullerenyldihydropyrrole 1 have been optimized to include acetic acid in the reaction mixture to rapidly protonate the anionic intermediate. Under these conditions, the ring opened dihydrofullerene 2 was obtained in 68% yield. Under slightly modified conditions and at −78 °C, the reductive bis-ring opening of the tethered trans-4 isomer 3 provided the novel racemic bis-dihydrofullerenyl derivative 7.     

Heterocycles from substituted amides II. Novel behavior of a reactive thiophene in some cyelo- and acyclo-addition reactions

N,N'-Diisopropyl-N,N'-diphenyl-2,4-thiophenediamine ( 1 ) has demonstrated its remarkable electron-donating abilities and atypical behavior as a thiophene, by its facile reaction with a number of electron deficient dienophiles. Thus, β-nitrostyrene, ethoxymethylene malononitrile, diethyl azodicarboxylate and dimethyl acetylenedicarboxylate undergo Michael-type addition at the 5-position of 1 to form adducts 2, 3, 4 , and 5 . Alternatively, the dienophiles, acrylonitrile, N-phenylrnaleimide and phenyl-1,2,4-triazoline-3,5-dione gave novel cyclic materials 6, 9 , and 11 , not necessarily arising from simple Diels Alder addition. Structure proofs for the products as well as alternative mechanisms for their formation are discussed.     

Synthesis and reactions of allenic amides : Allenes-XXXI

Allenic amides are prepared from allenic nitriles using alkaline hydrogen peroxide and by a Ritter reaction with t-butyl alcohol, when N-t-butylamides are obtained. Strong nucleophiles attack the central carbon of the allene system to give α,β-unsaturated addition products.     

Direct-type catalytic Mannich reactions of amides with imines

Direct-type catalytic Mannich reactions of amides with imines proceeded smoothly using barium phenoxide as a catalyst to afford the desired adducts in high yields with high anti selectivities.     

Catalytic silicon-mediated carbon-carbon bond-forming reactions of unactivated amides

In the presence of catalytic amounts of trialkylsilyl triflate and triethylamine, unactivated amides react with imines to afford the corresponding Mannich-type adducts in high yields with high anti selectivities. While silicon enolates have been widely used in organic synthesis for four decades, this is the first example of the catalytic use of the silicon species, to the best of our knowledge. Moreover, it is noteworthy that unactivated simple amides bearing α-protons that are less acidic than those of ketones and aldehydes can be successfully used in catalytic direct-type addition reactions. Finally, a preliminary trial of an asymmetric catalytic version was conducted and showed promising enantioselectivity of the desired product.