Aminoazanium of DABCO: An Amination Reagent for Alkyl and Aryl Pinacol Boronates

The aminoazanium of DABCO (H₂N‐DABCO) has been developed as a general and practical amination reagent for the direct amination of alkyl and aryl pinacol boronates. This compound is stable and practical for use as a reagent. Various primary, secondary. and tertiary alkyl?Bpin and aryl?Bpin substrates were aminated to give the corresponding amine derivatives. The amination is stereospecific. The anti‐Markovnikov hydroamination of olefins was easily achieved by catalytic hydroboration with HBpin and in subsequent situ amination using H₂N‐DABCO. Moreover, the combination of 1,2‐diboration of olefins, using B₂pin₂, with this amination process achieved the unprecedented 1,2‐diamination of olefins. The amination protocol was also successfully extended to aryl pinacol boronates.     

Copper‐Catalyzed N‐Arylation of Polysubstituted Pyridines Synthesized by the Novel Reaction of N‐Sulfonyl Ketenimine and Malononitrile‐Trichloroacetonitrile Adduct

In this study, we synthesized some new derivatives of N‐(4‐amino‐5‐cyano‐6‐(trichloromethyl)pyridin‐2‐yl)alkyl sulfonamides in the presence of a copper catalyst. A one‐pot reaction system was used, and four components participated in the process. These four components were sulfonyl azides, terminal alkynes, malononitrile, and trichloroacetonitrile. The reaction rate was increased by the use of copper (I) iodide as the catalyst and tetrahydrofuran was used as the solvent. We achieved the final compounds in moderate to good yields. Moreover, we converted “NH₂” side group to N‐aryl by the use of various aryl halide analogs in acetonitrile as the solvent, under mild reaction and at the room temperature.     

Intramolecular Amido Transfer Leading to Structurally Diverse Nitrogen‐Containing Macrocycles

Reported herein is the development of rhodium‐catalyzed intramolecular amido transfer as an efficient route to nitrogen‐containing macrocycles starting from acetophenone ketoximes tethered with either aryl or alkyl azides. Facile generation of rhodacycles and metal imido intermediates was the key to success in this mechanistic scaffold to represent the first example of an intramolecular inner‐sphere C−H amination. While substrates bearing aryl azides underwent a monomeric ring formation in high yields, a dimeric double cyclization took place exclusively with alkyl‐azide‐tethered ketoximes, thus affording up to 36‐membered azamacrocyclic products.     

Facile Synthesis of N‐Carboranyl Amines through an ortho‐Carboryne Intermediate

The efficient o‐carboryne precursor 1‐Li‐2‐OTf‐o‐C₂B₁₀H₁₀ reacts with lithium amides at room temperature to give a series of N‐carboranyl amines in moderate to high isolated yields. This reaction is compatible with a broad substrate scope from primary to secondary, alkyl to aryl amines. The reaction mechanism is also proposed on the basis of experimental results and DFT calculations. This represents the first general and efficient method for the synthesis of 1‐NR¹R²‐o‐carboranes.     

Manganese‐Catalyzed Oxidative Azidation of Cyclobutanols: Regiospecific Synthesis of Alkyl Azides by CC Bond Cleavage

A novel, manganese‐catalyzed oxidative azidation of cyclobutanols is described. A wide range of primary, secondary, and tertiary alkyl azides were generated in synthetically useful yields and exclusive regioselectivity. Aside from linear alkyl azides, otherwise elusive medium‐sized cyclic azides were also readily prepared. Preliminary mechanistic studies reveal that the reaction likely proceeds by a radical‐mediated C? C bond cleavage/C? N₃ bond formation pathway.     

Manganese‐Catalyzed Oxidative Azidation of Cyclobutanols: Regiospecific Synthesis of Alkyl Azides by C?C Bond Cleavage

A novel, manganese‐catalyzed oxidative azidation of cyclobutanols is described. A wide range of primary, secondary, and tertiary alkyl azides were generated in synthetically useful yields and exclusive regioselectivity. Aside from linear alkyl azides, otherwise elusive medium‐sized cyclic azides were also readily prepared. Preliminary mechanistic studies reveal that the reaction likely proceeds by a radical‐mediated C C bond cleavage/C N₃ bond formation pathway.     

N‐Heterocyclic Carbene Iron(III) Porphyrin‐Catalyzed Intramolecular C(sp3)–H Amination of Alkyl Azides

Metal‐catalyzed intramolecular C?H amination of alkyl azides constitutes an appealing approach to alicyclic amines; challenges remain in broadening substrate scope, enhancing regioselectivity, and applying the method to natural product synthesis. Herein we report an iron(III) porphyrin bearing axial N‐heterocyclic carbene ligands which catalyzes the intramolecular C(sp³)–H amination of a wide variety of alkyl azides under microwave‐assisted and thermal conditions, resulting in selective amination of tertiary, benzylic, allylic, secondary, and primary C?H bonds with up to 95 % yield. 14 out of 17 substrates were cyclized selectively at C4 to give pyrrolidines. The regioselectivity at C4 or C5 could be tuned by modifying the reactivity of the C5–H bond. Mechanistic studies revealed a concerted or a fast re‐bound mechanism for the amination reaction. The reaction has been applied to the syntheses of tropane, nicotine, cis‐octahydroindole, and leelamine derivatives.     

An Enolate‐Mediated Organocatalytic Azide–Ketone [3+2]‐Cycloaddition Reaction: Regioselective High‐Yielding Synthesis of Fully Decorated 1,2,3‐Triazoles

An enolate‐mediated organocatalytic azide–ketone [3+2]‐cycloaddition (OrgAKC) reaction of a variety of enolizable arylacetones and deoxybenzoins with aryl azides was developed for the synthesis of fully decorated 1,4‐diaryl‐5‐methyl(alkyl)‐1,2,3‐triazoles in excellent yields with high regioselectivity at 25 °C for 0.5–6 h. This reaction has an excellent outcome with reference to reaction rate, yield, regioselectivity, operation simplicity, and availability of substrates and catalyst. This reaction has advantages over the previously known metal‐mediated reactions.     

Formal [4+2]‐Annulation of Vinyl Azides with N‐Unsaturated Aldimines

Highly functionalized quinolines and pyridines could be synthesized by BF₃?OEt₂‐mediated reactions of vinyl azides with N‐aryl and N‐alkenyl aldimines, respectively. The reaction mechanism could be characterized as formal [4+2]‐annulation, including unprecedented enamine‐type nucleophilic attack of vinyl azides to aldimines and subsequent nucleophilic cyclization onto the resulting iminodiazonium ion moieties.     

Selective Monoarylation of Primary Amines Using the Pd‐PEPPSI‐IPentCl Precatalyst

A single set of reaction conditions for the palladium‐catalyzed amination of a wide variety of (hetero)aryl halides using primary alkyl amines has been developed. By combining the exceptionally high reactivity of the Pd‐PEPPSI‐IPent^Cl catalyst (PEPPSI=pyridine enhanced precatalyst preparation, stabilization, and initiation) with the soluble and nonaggressive sodium salt of BHT (BHT=2,6‐di‐tert‐butyl‐hydroxytoluene), both six‐ and five‐membered (hetero)aryl halides undergo efficient and selective amination.     

Chemoselective Aromatic Azido Reduction with Concomitant Aliphatic Azide Employing Al/Gd Triflates/NaI and ESI‐MS Mechanistic Studies

Aluminium and gadolinium triflates catalyze the chemoselective reduction of aromatic azides to the corresponding amines in combination with sodium iodide. This mild chemoselective method has been applied to the synthesis of various aryl amines, C2‐azido‐substituted pyrrolo[2,1‐c][1,4]benzodiazepines, and fused[2,1‐b]quinazolinones by an intramolecular azido reduction tandem cyclization reaction. Interestingly, this methodology selectively reduces aryl azides with enhanced yields and proceeds in shorter reaction times than previous strategies. The mechanistic aspects have been investigated and the intermediates associated with this selective transformation have been intercepted and characterized by online monitoring of the reaction by ESI‐MS.     

From azides to nitriles. A novel fast transformation made possible by BrF3

[reaction: see text]. Various alkyl and aryl azides, readily obtained from halides or alcohols, were transformed into the corresponding nitriles using bromine trifluoride in moderate to good yields. The reaction is general and gives positive results with aliphatic, aromatic, cyclic, and functionalized azides. It can also be applied to the synthesis of optically active nitriles.     

Ortho-Phosphinoarenesulfonamide-Mediated Staudinger Reduction of Aryl and Alkyl Azides

Conventional Staudinger reductions of organic azides are sluggish with aryl or bulky aliphatic azides. In addition, Staudinger reduction usually requires a large excess of water to promote the decomposition of the aza-ylide intermediate into phosphine oxide and amine products. To overcome the challenges above, we designed a novel triaryl phosphine reagent 2c with an ortho-SO₂NH₂ substituent. Herein, we report that such phosphine reagents are able to mediate the Staudinger reduction of both aryl and alkyl azides in either anhydrous or wet solvents. Good to excellent yields were obtained in all cases (even at a diluted concentration of 0.01 M). The formation of B-TAP, a cyclic aza-ylide, instead of phosphine oxide, eliminates the requirement of water in the Staudinger reduction. In addition, computational studies disclose that the intramolecular protonation of the aza-ylide by the ortho-SO₂NH₂ group is kinetically favorable and responsible for the acceleration of Staudinger reduction of the aryl azides.     

Electrophilic amination of diorganozinc reagents by oxaziridines

Electrophilic amination of organozinc reagents by oxaziridines has been studied. Diorganozinc reagents R₂Zn (R = alkyl or aryl) react with N-Boc oxaziridine to afford N-Boc protected primary amines BocNHR in moderate to good yields. No additives are needed in this reaction, which proceeds at 0 °C. We suggest that the presence of two heteroatoms in oxaziridine allows Lewis base activation of the diorganozinc reagent.     

Copper(II) Acetylacetonate: An Efficient Catalyst for Huisgen‐Click Reaction for Synthesis of 1,2,3‐Triazoles in Water

An efficient and green copper(II ) acetylacetonate‐catalyzed protocol for the Huisgen‐click reaction in water at 100 °C has been established. The protocol was not only suitable for the reaction between organic azides and alkynes, but also suitable for one‐pot three‐component reaction among alkyl halides, NaN₃ and alkynes.     

Chloromethylated polystyrene supported copper (II) bis–thiazole complex: Preparation,characterization and its application as a heterogeneous catalyst for chemoselective and homoselective synthesis of aryl azides

This work deals the synthesis of aryl azides catalyzed by heterogeneous copper (II) complex of 3,5–bis (2–benzothiazolyl) pyridine, [Cu (II)(BTP)(OTf)₂], immobilized on chloromethylated polystyrene, [Cu (II)(BTP)(OTf)₂]@CMP. The prepared catalyst was characterized by different analytical techniques such as X‐ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (SEM), energy dispersive X–ray spectroscopy (EDX), elemental analysis, and FT‐IR and UV–Vis spectroscopic methods. This catalytic system showed excellent activity in the synthesis of aryl azides by the reaction of aryl halides with sodium azide in the presence of catalytic amounts of [Cu (II)(BTP)(OTf)₂]@CMP. Moreover, this unique catalyst could be recovered easily and reused several times without any considerable loss of its catalytic activity.     

New Pyrazolyl‐Nicotinic Acids,Methyl Esters,and 1,3,4‐Oxadiazolyl‐pyrazolyl‐pyridine Tricyclic Scaffold Derivatives from 6‐Hydrazinylnicotinic Acid Hydrazide Hydrate

This paper describes an efficient approach for the synthesis of a new series of 6‐[3‐alkyl(aryl/heteroaryl)‐5‐trifluoromethyl‐1H‐pyrazol‐1‐yl]nicotinic acids (where alkyl = CH₃; aryl = Ph, 4‐OCH₃Ph, 4,4′‐BiPh; and heteroaryl = 2‐Furyl) from the hydrolysis reaction of alkyl(aryl/heteroaryl)substituted 2‐(5‐trifluoromethyl‐5‐hydroxy‐4,5‐dihydro‐1H‐pyrazol‐1‐yl)‐5‐(5‐trifluoromethyl‐5‐hydroxy‐4,5‐dihydro‐1H‐1‐carbonylpyrazol‐1‐yl)pyridines, under basic conditions and at 70–95% yields. In a subsequent step, the esterification reaction of pyrazolyl‐nicotinic acids done in thionyl chloride and methanol led to the isolation of a series of methyl 6‐[alkyl(aryl/heteroaryl)‐5‐trifluoromethyl‐1H‐pyrazol‐1‐yl] nicotinates as stable hydrochloride salts at 64–84% yields, which could be easily converted to hydrazides to give new oxadiazolyl‐pyrazolyl‐pyridine tricyclic scaffolds at good yields from a [4 + 1] cyclocondensation reaction with 1,1,1‐triethoxyethane and 1‐(triethoxymethyl)benzene as the reagent/solvent.     

Tandem Coupling of Azide with Isonitrile and Boronic Acid: Facile Access to Functionalized Amidines

Amidine is a notable nitrogen‐containing structural motif found in bioactive natural products and pharmaceuticals. Herein, a novel rhodium(I)‐catalyzed tandem reaction of readily accessible azides with isonitriles and boronic acids via a carbodiimide intermediate is achieved. This protocol offers an alternative approach toward N‐sulfonyl‐, N‐acyl‐, and N‐ phosphoryl‐functionalized, as well as general N‐aryl and N‐alkyl amidines with broad substrate scope. In addition, functionalized guanidines can also been synthesized when amines are used instead. The accomplishment of estrone‐derived amidine and glibenclamide bioisosteres further reveals the practical utility of this strategy.     

[FeIII(F20‐tpp)Cl] Is an Effective Catalyst for Nitrene Transfer Reactions and Amination of Saturated Hydrocarbons with Sulfonyl and Aryl Azides as Nitrogen Source under Thermal and Microwave‐Assisted Conditions

[Fe^III(F₂₀‐tpp)Cl] (F₂₀‐tpp=meso‐tetrakis(pentafluorophenyl)porphyrinato dianion) is an effective catalyst for imido/nitrene insertion reactions using sulfonyl and aryl azides as nitrogen source. Under thermal conditions, aziridination of aryl and alkyl alkenes (16 examples, 60–95 % yields), sulfimidation of sulfides (11 examples, 76–96 % yields), allylic amidation/amination of α‐methylstyrenes (15 examples, 68–83 % yields), and amination of saturated C? H bonds including that of cycloalkanes and adamantane (eight examples, 64–80 % yields) can be accomplished by using 2 mol % [Fe^III(F₂₀‐tpp)Cl] as catalyst. Under microwave irradiation conditions, the reaction time of aziridination (four examples), allylic amination (five examples), sulfimidation (two examples), and amination of saturated C? H bonds (three examples) can be reduced by up to 16‐fold (24–48 versus 1.5–6 h) without significantly affecting the product yield and substrate conversion.     

Radical amination with sulfonyl azides: a powerful method for the formation of C-N bonds

A novel reaction for the introduction of an azide moiety by means of a mild radical process is currently under development. Sulfonyl azides are suitable azidating agents for nucleophilic radicals, such as secondary and tertiary alkyl radicals. More electrophilic radicals, such as enolate radicals, do not react with sulfonyl azides. This feature allowed the development of efficient intra- and intermolecular carboazidations of olefins. Due to the versatility of the azido group, this reaction has an important synthetic potential, as already demonstrated by the preparation of the core of several alkaloids, particularly those containing an amino-substituted quaternary carbon center, such as FR901483.