Synthesis of N,N-dialkylaminobenzonitriles and halo-(N,N-dialkyl)benzamidines by reaction of halobenzonitriles with lithium amides

3- and 4-N,N-Dialkylaminobenzonitriles and 4-chloro-(N,N-dialkyl)benzamidines were isolated by reacting 4-chlorobenzonitrile with hindered lithium amides under thermodynamic (0 °C) and kinetic control conditions (−78 °C), respectively. As previously reported, a benzyne mechanism seems to be confirmed since N,N-dialkylaminobenzonitriles are formed. Only benzamidines were isolated in fair to high yields at both 0 °C and −78 °C with non-hindered lithium amides. Exploitation and mechanistic rationale of the reaction of different halobenzonitriles are also reported.     

N-[1-(Benzotriazol-1-yl)alkyl]amides from N-acyl-α-amino acids or N-alkylamides

A variety of N-(1-methoxyalkyl)amides react with benzotriazole in the presence of PPh₃·HBF₄ and organic bases (Hünig's base, DBU or DABCO) or solid-state-supported bases (SiO₂-Pip or IRA-67) in CHCl₃ to give N-[1-(benzotriazol-1-yl)alkyl]amides in good yields. The most convenient and efficient procedure for obtaining N-[1-(benzotriazol-1-yl)alkyl]amides consists, however, of the addition of benzotriazole sodium salt to a solution of crude 1-(N-acylamino)alkyltriphenylphosphonium salt, obtained in situ from N-(1-methoxyalkyl)amides and PPh₃·HBF₄. A combination of these reactions with the recently described electrochemical decarboxylative α-methoxylation of N-acyl-α-amino acids in the presence of SiO₂-Pip enables an effective two-pot transformation of N-acyl-α-amino acids to N-[1-(benzotriazol-1-yl)alkyl]amides.     

Facile synthesis of acyclic azanucleosides from N-pivaloyloxymethyl amides and sulfonamides: synthesis of aza-analogues of Ganciclovir

N-Pivaloyloxymethyl amides and sulfonamides, readily available from N-alkylation of both amides and sulfonamides with commercial chloromethyl pivaloate, were converted into acyclic azanucleosides via a one-pot base silylation/nucleoside coupling procedure.     

Palladium-catalyzed stereoselective synthesis of (E)-β,γ-unsaturated amides

A facile Suzuki type cross-coupling reaction of alkenylborane with 2-bromo-N,N-dimethylacetamide in the presence of a catalytic amount of tricyclohexylphosphine as the ligand has been demonstrated to be a convenient way for the synthesis of (E)-β,γ-unsaturated amides.     

Ruthenium-catalyzed reduction of N-alkoxy- and N-hydroxyamides

A ruthenium-catalyzed reduction of N-alkoxy- and N-hydroxyamides was found to afford corresponding amides in good to high yields. A simple RuCl₃/Zn-Cu/alcohol system, without the addition of any other ligands, exhibited a high catalytic activity, and therefore the present reaction does not require a stoichiometric amount of metals or metal complexes as reductants. When β-substituted-α,β-unsaturated N-methoxyamides were employed as substrates, concurrent hydrogenation of the olefin moiety proceeded slowly with deprotection of the methoxy group. In the reduction of N-hydroxyamides, the alcoholic solvent was found to function as a hydrogen donor.     

Simple and efficient cleavage of the N-(1-phenylethyl) unit of carboxamides with methanesulfonic acid

Cleavage of the N-(1-phenylethyl) unit of carboxamides using less than 1 equiv of MsOH in refluxing toluene was found to be simple and very efficient leading to the desired amides in good to excellent yields, and also proved to be more effective compared with reductive methods using hydrogen sources, or acid hydrolysis reagents such as TFA and TsOH. The method selectively cleaved only the N-(1-phenylethyl) group of N-benzyl-N-(1-phenylethyl)amides.     

Moderate generation of sulfenylnitrenes from novel N-sulfenylsulfodiimides

N-Sulfenylated sulfodiimides were first prepared by the reaction of S,S-diphenyl-N-tosylsulfodiimide with arenesulfenyl chlorides under the basic conditions. Thermolysis of S,S-diphenyl-N-(2-nitrophenylsulfenyl)- and S,S-diphenyl-N-(2,4-dinitrophenylsulfenyl)sulfodiimides in the presence of olefins proceeded at 50-80 °C to give the corresponding deiminated S,S-diphenyl-N-tosylsulfimide and N-sulfenylaziridines in very good yields. 2,4-Dinitrophenyl-sulfenylnitrene was trapped by trans- and cis-1-phenylpropenes stereospecifically. The thermolysis temperature of the N-sulfenylsulfodiimides was found to be lower than N-sulfenylsulfoximide and higher than N-sulfenyliminosulfonium salt and very effective to trap the sulfenylnitrene to give the N-sulfenylaziridines in very good yields.     

Hydro-amination/-amidation of 1,3-diynes with indoles/azoles/amides under modified Ullmann conditions: stereo- and regio-selective synthesis of N-alkenynes via N-H bond activation

An efficient strategy for the stereo- and regio-selective synthesis of N-alkenynes has been described. The salient feature of the reaction involves hydro-amination/amidation of 1,3-diynes with indoles/azoles/amides via transition-metal catalyzed activation of N-H bond. The resulting N-alkenynes derived from N-heterocycles and cyclic amides were obtained as a mixture of Z/E isomers with Z-stereoselectivity ranging from 60% to 95%. In contrast, acyclic amides afforded N-alkenynes with exclusive E-stereoselectivity, albeit in reduced yield ranging from ∼10% to 41%.     

Practical and efficient synthesis of N-halo compounds

A practical and efficient synthesis of N-halo compounds is described. Treatment of primary and secondary amines or amides with sodium hypohalite in the presence of tert-butanol and acetic acid afforded N-halo compounds in 90-100% yield.     

Reaction of difluorocarbene with anions from amides and oximes: Synthesis of N-difluoromethyl substituted amides, O-difluoromethylimidates or O-difluoromethyl substituted oximes under phase-transfer catalysis conditions

N-Aryl substituted amides react with chlorodifluoromethane in the presence of concentrated aqueous sodium hydroxide and benzyltriethylammonium chloride (TEBAC) as a catalyst in benzene (phase-transfer catalysis, PTC), affording mixtures of N- and O-difluoromethyl substituted derivatives. Amide anions are involved in this process. The reaction carried out with oximes gives O-difluoromethyl oxime ethers.     

A CAN-initiated aza-Diels-Alder reaction for a facile synthesis of 4-amido-N-yl tetrahydroquinolines

Cycloaddition of N-arylimines with N-vinylpyrrolidin-2-one or N-methyl-N-vinylacetamide was efficiently initiated by cerium(IV) ammonium nitrate (CAN), and produced stereoselectively the corresponding 2,4-cis-4-amido-N-yl tetrahydroquinoline derivatives in good yields.     

A novel, one-pot, three-component synthesis of 4H-pyrido[1,2-a]pyrimidines

A novel, one-pot, three-component synthesis of 4H-pyrido[1,2-a]pyrimidines is described. The reactive 1:1 zwitterionic intermediate, formed by the addition of isocyanides to dialkyl acetylenedicarboxylates, was trapped by N-(2-pyridyl)amides to produce the title compounds under mild reaction conditions in good yields.     

Enzymatic synthesis of N-acylethanolamines: direct method for the aminolysis of esters

Immobilized Candida antarctica (Novozyme 435) catalyzed synthesis of N-acylethanolamines is described. Treatment of methyl esters with lipase and amines yielded the desired amides within 2-24 h with yields ranging from 41% to 98%.     

Superelectrophilic activation of N-aryl amides of 3-arylpropynoic acids: synthesis of quinolin-2(1H)-one derivatives

The superelectrophilic activation of N-aryl amides of 3-arylpropynoic acids by Bronsted superacids (CF₃SO₃H, HSO₃F) or strong Lewis acids AlX₃ (X=Cl, Br) results in the formation of 4-aryl quinolin-2(1H)-ones in quantitative yields. The vinyl triflates or vinyl chlorides may be formed as additional reaction products. The investigated amides in reactions with benzene give 4,4-diaryl 3,4-dihydroquinolin-2-(1H)-ones under the superelectrophilic activation. 4-Aryl quinolin-2(1H)-ones in POCl₃ are converted into 4-aryl 2-chloroquinolines. 4-Fluorophenyl-4-phenyl 3,4-dihydroquinolin-2-(1H)-one give N-formylation products in a yield of 79% under the Vilsmeier–Haack reaction conditions.     

Elimination of benzotriazolyl group in N-(α-benzotriazol-1-ylalkyl)amides and N-(α-benzotriazol-1-ylalkyl)sulfonamides: their self-coupling and cross-coupling reactions with carbonyl compounds

The elimination of benzotriazolyl group from N-(α-benzotriazol-1-ylalkyl)amides and N-(α-benzotriazol-1-ylalkyl)sulfonamides are readily realized with samarium diiodide as a reducing agent. The resulting intermediates undergo a dimerization or cross-coupling reaction with carbonyl compounds, thus affording the corresponding dimers or α-hydroxyalkylated sulfonamides in moderate yields.     

Facile rearrangement of N-(α-aminoacyl)cytidines to N-(4-cytidinyl)amino acid amides

Under near neutral and mildly basic conditions, primary N⁴-(α-aminoacyl)cytidines (4a-g) undergo a facile rearrangement to form N-(4-cytidinyl)amino acid amides (5a-g). Secondary aminoacyl derivatives rearrange with other competing pathways. Tertiary aminoacyl derivatives do not rearrange.     

Transition-metal-free approach to synthesis of indolines from N-(ortho-chloromethyl)aryl amides and iodonium ylides

A transition-metal-free method for the synthesis of indolines has been developed. In the presence of K₂CO₃, the cyclization reaction of N-(ortho-chloromethyl)aryl amides and iodonium ylides proceeded smoothly at room temperature in moderate to good yields.     

Stereoselective fluorination of methylenecyclopropanes with N-F reagents: A modular entry to γ-fluorohomoallylic sulfonimides and γ-fluorohomoallylic amides

A convenient and efficient method for fluorination of methylenecyclopropanes is reported. This is exemplified in the stereoselective preparation of N-[(E)-3-fluorobut-3-en-1-yl]-benzenesulfonimides by the reaction of methylenecyclopropanes with N-fluorobenzenesulfonimide in good to excellent yields. Moreover, γ-fluorohomoallylic amides are synthesized using Selectfluor in R₃CN at 60 °C.     

Acyclic tertiary diamines and 1,4,7,10-tetraazacyclododecane with fluorine-containing β-diketones: Leading to low melting ionic adducts

N,N,N′,N′-Tetramethylmethanediamine (1a), N,N,N′,N′-tetramethylethanediamine (1b), N,N,N′,N′-tetramethyl-1,3-propanediamine (1c), and N,N,N′,N′-tetramethyl-1,6-hexanediamine (1d) were reacted at 25 °C with 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (2a), 2,2-dimethyl-6,6,7,7,8,8,8-heptafluoro-3,5-octanedione (2b), 2-thenoyltrifluoroacetone (2c), and 4,4,4-trifluoro-1-(2-furyl)-1,3-butanedione (2d) to form the ionic adducts 3-18. 1,4,7,10-Tetraazacyclododecane (1e) reacted at 25 °C with β-diketones (2a-d) and 1,1,1-trifluoro-2,4-pentanedione (2e) to give ionic solids 19-23 in good yields. Some of the products are liquid at 25 °C and are thermally stable over long liquid ranges as determined by thermal gravimetric analyses. Single-crystal X-ray structure determinations show that compounds 9 and 21 crystallize in the monoclinic space groups P2(1)/c and P2(1)/n, respectively. All the new compounds were characterized by ¹H, ¹⁹F and ¹³C NMR, electrospray MS and/or elemental analyses.     

Synthesis of N-acyl-N,O-acetals from N-aryl amides and acetals in the presence of TMSOTf

Secondary amides undergo in situ silyl imidate formation mediated by TMSOTf and an amine base, followed by addition to acetal acceptors to provide N-acyl-N,O-acetals in good yields. An analogous, high-yielding reaction is observed with 2-mercaptothiazoline as the silyl imidate precursor. Competing reduction of the acetal to the corresponding methyl ether via transfer hydrogenation can be circumvented by the replacement of CY₂NMe with 2,6-lutidine under otherwise identical reaction conditions.