From Nef‐Isocyanide Adducts toward Functionalized 5‐Iminothiazolidines Containing Polarized CC Bonds

An efficient synthesis of alkyl 5‐(alkylimino)‐3‐aryl(alkyl)‐2‐(dicyanomethylene)‐4‐hydroxythiazolidine‐4‐carboxylates, containing polarized C?C bonds, via reaction of malononitrile, arylisothiocyanates, and the Nef‐isocyanide adducts, under basic conditions, is described.     

Formation of Dialkyl 2‐[3‐Alkoxy‐1‐(alkylimino)‐1‐chloro‐3‐oxopropan‐2‐ylidene]hydrazine‐1,1‐dicarboxylates of α‐(Alkoxycarbonyl)imidoyl Chlorides from PhosphineDiazo Ester Zwitterions and Nef‐Isocyanide Adducts

A novel transformation involving phosphine? diazo ester zwitterions (generated from dialkyl azodicarboxylates with Ph₃P) and α‐(alkoxycarbonyl)imidoyl chlorides (prepared from α‐addition of acyl chlorides to alkyl isocyanides) to afford dialkyl 2‐[3‐alkoxy‐1‐(alkylimino)‐1‐chloro‐3‐oxopropan‐2‐ylidene]hydrazine‐1,1‐dicarboxylates in moderate yields, is described.     

Synthesis of 1,3,5‐Triazepineselone Derivatives from Acyl Isoselenocyanates and Benzene‐1,2‐diamine

Tandem reaction between acyl isoselenocyanates, generated from acyl chlorides and KSeCN, and benzene‐1,2‐diamine in acetone at room temperature, gave 1,3,5‐triazepineselone derivatives in moderate to good yields.     

Copper‐Catalyzed One‐Pot Synthesis of Functionalized Pyrroles from Sulfonyl Azides,Alkynes, and (p‐Toluenesulfonyl)methyl Isocyanide

Ketenimine intermediates generated by the addition of copper acetylides to sulfonyl azides are trapped by (p‐toluenesulfonyl)methyl isocyanide (TsCH₂NC), in the presence of Et₃N, to afford functionalized pyrroles in moderate‐to‐good yields.     

Synthesis and Biological Activity of Some New Pyrazolo[3,4‐b]Pyrazines

New derivatives of pyrazolo[3,4‐b]pyrazine and related heterocycles were prepared starting from 6‐amino‐3‐methyl‐1‐phenyl‐1H‐pyrazolo[3,4‐b]pyrazine‐5‐carbonitrile ( 2 ) and using the key intermediates 4 , 5 , 6 , 14 , 15 and 16 . Some of the prepared compounds were evaluated for their antifungal and antibacterial activities.     

Catalyst‐Free Protocol for the Synthesis of Quinoxalines and Pyrazines in PEG

A facile and simple catalyst‐free protocol has been developed for the condensation of 1,2‐diketones with aromatic 1,2‐diamines in polyethylene glycol (PEG), providing quinoxaline derivatives in good yields. The important features of the methodology are broad substrates scope, simple workup, catalyst free, environmentally benign, and no requirement for metal catalysts. It is noteworthy that the cyclization reaction of 1,2‐diketones with aliphatic 1,2‐diamines is also conducted smoothly to afford pyrazines in good yields under the standard conditions. In addition, PEG could be recovered easily and was reused without evident loss in activity     

Convenient Synthesis of Functionalized 3,4,10,11‐tetrahydroindolo[1,2‐a]Quinoxalines Via Three‐component Reaction of Dimedone, 3‐nitrochromenes and Ammonium Acetate

An efficient synthetic procedure for the functionalized 3,4,10,11‐tetrahydroindolo[1,2‐a]quinoxalines was successfully developed by the three‐component reaction of dimedone, 3‐nitrochromenes, and ammonium acetate in ethanol. This reaction has the advantages of using common starting material, short reaction process, and good yields high‐atom efficiency.     

One‐Pot Synthesis of 1,4‐Oxathiino[2,3‐b]quinoxalines or ‐pyrazines from 2,3‐Dichloroquinoxaline or ‐pyrazine and 1‐Aryl‐2‐bromoalkan‐1‐ones

An efficient one‐pot synthesis of novel heterocyclic derivatives, 2‐aryl‐1,4‐oxathiino[2,3‐b]quinoxalines or ‐pyrazines 5 , via the reaction of 2,3‐dichloroquinoxaline or ‐pyrazine with Na₂S?9 H₂O, and subsequent treatment of the resulting 2‐chloro‐3‐sodiosulfanylquinoxaline or ‐pyrazine 2 with 1‐aryl‐2‐bromo‐1‐alkanones and then NaH under mild conditions is described.     

Regio‐ and Enantioselective Formal Hydroamination of Enamines for the Synthesis of 1,2‐Diamines

The asymmetric formal hydroamination of enamines using a CuH catalyst is reported. The method provides a straightforward and efficient approach to the synthesis of chiral 1,2‐dialkyl amines in good yields with high levels of enantioselectivities for a broad range of substrates, and should have significant value for the preparation of molecules bearing a 1,2‐diamine motif.     

Nef‐Isocyanide ‐Based One‐pot Two‐step Three Component Dihydrobenzo[4,5]Imidazo[2,1‐b]thiazoles Synthesis

The reactive imidoyl chloride adducts generated in situ from the reaction of isocyanide and acyl chlorides were trapped by 2‐mercaptobenzimidazoles to yield highly functionalized dihydrobenzo[4,5]imidazo[2,1‐b]thiazoles in good yields.     

The Synthesis of Benzimidazoles and Quinoxalines from Aromatic Diamines and Alcohols by Iridium‐Catalyzed Acceptorless Dehydrogenative Alkylation

Benzimidazoles and quinoxalines are important N‐heteroaromatics with many applications in pharmaceutical and chemical industry. Here, the synthesis of both classes of compounds starting from aromatic diamines and alcohols (benzimidazoles) or diols (quinoxalines) is reported. The reactions proceed through acceptorless dehydrogenative condensation steps. Water and two equivalents of hydrogen are liberated in the course of the reactions. An Ir complex stabilized by the tridentate P^N^P ligand N²,N⁶‐bis(di‐isopropylphosphino)pyridine‐2,6‐diamine revealed the highest catalytic activity for both reactions.     

Reactions of Cyclohexyl Isocyanide with η5‐Substituted Cyclo‐pentadienyl MoMo Triply Bonded Complexes. Crystal Structure of [Mo(CO)2(η5‐C5H4CO2CH3)]2(μ‐η2‐CNC6H11)

Reactions of one or two equiv. of cyclohexyl isocyanide in THF at room temperature with Mo?Mo triply bonded complexes [Mo(CO)₂(η⁵‐C₅H₄R)]₂ (R=COCH₃, CO₂CH₃) gave the isocyanide coordinated Mo? Mo singly bonded complexes with functionally substituted cyclopentadienyl ligands, [Mo(CO)₂(η⁵‐C₅H₄R)]₂(μ‐η²‐CNC₆H₁₁) ( 1a , R=COCH₃; 1b , R=CO₂CH₃) and [Mo(CO)₂(η⁵‐C₅H₄R)(CNC₆H₁₁)]₂ ( 2a , R=COCH₃; 2b , R=CO₂CH₃), respectively. Complexes 1a , 1b and 2a , 2b could be more conveniently prepared by thermal decarbonylation of Mo? Mo singly bonded complexes [Mo(CO)₃(η⁵‐C₅H₄R)]₂ (R=COCH₃, CO₂CH₃) in toluene at reflux, followed by treatment of the resulting Mo?Mo triply bonded complexes [Mo(CO)₂(η⁵‐C₅H₄R)]₂ (R=COCH₃, CO₂CH₃) in situ with cyclohexyl isocyanide. While 1a , 1b and 2a , 2b were characterized by elemental analysis and spectroscopy, 1b was further characterized by X‐ray crystallography.     

One‐Pot Synthesis of N‐Substituted β‐Amino Alcohols from Aldehydes and Isocyanides

A practical two‐stage one‐pot synthesis of N‐substituted β‐amino alcohols using aldehydes and isocyanides as starting materials has been developed. This method features mild reaction conditions, broad scope, and general tolerance of functional groups. Based on a less common central carbon–carbon bond disconnection, this protocol complements traditional approaches that involve amines and various carbon electrophiles (epoxides, α‐halo ketones, β‐halohydrins). Medicinally relevant products can be prepared in a concise and efficient way from simple building blocks, as demonstrated in the synthesis of the antiasthma drug salbutamol. Upgrading the synthesis to an enantioselective variant is also feasible.     

Palladium‐ and Solvent‐Free Synthesis of Ynones by Copper(I)‐Catalyzed Acylation of Terminal Alkynes with Acyl Chlorides under Aerobic Conditions

Air‐stable Cu^I/cryptand‐22 complex was found to be a highly active catalyst for the solvent‐free cross‐coupling reaction of terminal alkynes with different acyl chlorides in the presence of Et₃N as base to give the corresponding ynones in quantitative yields.     

Design and Synthesis of Isocyanide Ligands for Catalysis: Application to Rh‐Catalyzed Hydrosilylation of Ketones

New isocyanide ligands with meta‐terphenyl backbones were synthesized. 2,6‐Bis[3,5‐bis(trimethylsilyl)phenyl]‐4‐methylphenyl isocyanide exhibited the highest rate acceleration in rhodium‐catalyzed hydrosilylation among other isocyanide and phosphine ligands tested in this study. ¹H NMR spectroscopic studies on the coordination behavior of the new ligands to [Rh(cod)₂]BF₄ indicated that 2,6‐bis[3,5‐bis(trimethylsilyl)phenyl]‐4‐methylphenyl isocyanide exclusively forms the biscoordinated rhodium–isocyanide complex, whereas less sterically demanding isocyanide ligands predominantly form tetracoordinated rhodium–isocyanide complexes. FTIR and ¹³C NMR spectroscopic studies on the hydrosilylation reaction mixture with the rhodium–isocyanide catalyst showed that the major catalytic species responsible for the hydrosilylation activity is the Rh complex coordinated with the isocyanide ligand. DFT calculations of model compounds revealed the higher affinity of isocyanides for rhodium relative to phosphines. The combined effect of high ligand affinity for the rhodium atom and the bulkiness of the ligand, which facilitates the formation of a catalytically active, monoisocyanide–rhodium species, is proposed to account for the catalytic efficiency of the rhodium–bulky isocyanide system in hydrosilylation.     

Synthesis and properties of phosphorus containing polyester‐amides derived from 1,4‐bis(3‐aminobenzoyloxy)‐2‐(6‐oxido‐6H‐dibenz〈c,e〉〈1,2〉oxaphosphorin‐6‐yl) phenylene

A series of polyester‐amides that contain phosphorus were synthesized by low temperature solution condensation of 1,4‐bis(3‐aminobenzoyloxy)‐2‐(6‐oxido‐6H‐dibenz〈c,e〉〈1,2〉oxaphosphorin‐6‐yl) phenylene (III) with various aromatic acid chlorides in N‐methyl pyrrolidone (NMP). All polyester‐amides are amorphous and readily soluble in many organic solvents such as dimethylacetamide (DMAc), NMP, dimethylsulfoxide, and dimethylformamide at room temperature or on heating. Light yellow and flexible films of these polyester‐amides could be cast from the DMAc solutions. The polymers with an inherent viscosity of 0.26–0.72 dL/g were obtained in quantitative yields. These polyester‐amides have good mechanical properties (G′ of ∼ 10⁹ Pa up to 200°C) and good thermal and flame retardant properties. The glass transition temperatures of these polyester‐amides ranged from 250 to 273°C. The degradation temperatures (T_d 5%) in nitrogen ranged from 466 to 478°C and the char yields at 800°C were 59.6–65.2%. The limiting oxygen indexes of these polyester‐amides ranged from 35 to 43. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 891–899, 1999     

Chiral Calcium–BINOL Phosphate Catalyzed Diastereo‐ and Enantioselective Synthesis of syn‐1,2‐Disubstituted 1,2‐Diamines: Scope and Mechanistic Studies

A highly enantioselective, chiral, Lewis acid calcium–bis(phosphate) complex, Ca[ 3 a ]_n, which catalyzes the electrophilic amination of enamides with azodicarboxylate derivatives 2 to provide versatile chiral 1,2‐hydrazinoimines 4 is disclosed. The reaction gives an easy entry to optically active syn‐1,2‐disubstituted 1,2‐diamines 6 in high yields with excellent enantioselectivities, after a one‐pot reduction of the intermediate 1,2‐hydrazinoimines 4 . The geometry and nature of the N‐substituent of the enamide affect dramatically both the reactivity and the enantioselectivity. Although the calcium–bis(phosphate) complex was a uniquely effective catalyst, the exact nature of the active catalytic species remains unclear. NMR spectroscopy and MS analysis of the various calcium complexes Ca[ 3 ]_n reveals that the catalysts exist in various oligomer forms. The present mechanistic study, which includes nonlinear effects and kinetic measurements, constitutes a first step in understanding these calcium–bis(phosphate) complex catalysts. DFT calculations were carried out to explore the mechanism and the origin of the enantioselectivity with the Ca[ 3 ]_n catalysts.