NaIO4/LiBr-mediated aziridination of olefins using chloramine-T

A new milder protocol for aziridination of a variety of olefins has been described. The process employs catalytic amount of sodium metaperiodate (NaIO₄) as an oxidant and LiBr and chloramine-T as the bromine and nitrogen sources, respectively. Interestingly, the formation of aziridine products in all the cases studied takes place presumably through a process of 1,2-aminobromination of alkenes.     

Palladium(II) mediated aziridination of olefins with bromamine-T as the nitrogen source: scope and mechanism

The palladium(II)-promoted reaction of a variety of olefins and bromamine-T provided N-tosyl-2-substituted aziridines under mild conditions. Olefins bearing chiral appendages gave only a poor to modest diastereoselectivity. Appropriate deuterated olefins were selected to study the stereochemistry of the reaction. A Pd(IV) intermediate is proposed as the aziridinating species.     

Highly efficient and metal-free oxidation of olefins by molecular oxygen under mild conditions

Highly efficient and metal-free aerobic oxidations of cyclohexene and styrene were successfully performed under mild conditions in the presence of 1,4-diamino-2,3-dichloro-anthraquinone and N-hydroxyphthalimide. When cyclohexene was oxidized, an 89% conversion and 71% selectivity for 2-cyclohexen-1-one was obtained under 0.3 MPa at 80 °C for 5 h. In the oxidation of styrene, a 77% conversion and 69% selectivity for benzaldehyde was obtained for 10 h. Furthermore, more olefins were efficiently oxidized to corresponding oxygenated products under mild conditions. All kinds of factors that affected cyclohexene oxidation were well investigated, and the possible reaction mechanism was provided.     

A chemoselective deoxygenation of N-oxides by sodium borohydride-Raney nickel in water

A simple and convenient protocol for deoxygenation of aliphatic and aromatic N-oxides to the corresponding amines in good to excellent yield using sodium borohydride-Raney nickel in water is reported. Other functional moieties such as alkenes, halides, ethers, and amides are unaffected under the present reaction condition.     

Oxidative addition of N-aminophthalimide to thiophene and selenophene: the first example of a 5-thia(seleno)-3,7-diazatricyclo[4.1.0.0]heptane system

The first examples of condensed saturated heterocycles containing a central tricyclic bisaziridine core were obtained by oxidative addition of N-aminophthalimide to thiophene and selenophene. Their structures and spectral features are described.     

Metal-free oxidative amide formation with N-hydroxysuccinimide and hypervalent iodine reagents

An oxidative amide formation using N-hydroxysuccinimide and hypervalent iodine reagents was developed. The method enables a wide range of aldehydes and amines to be coupled under mild reaction conditions providing amide in good to excellent yield. The radical species in the reaction mixture was observed for the first time using ESR measurement, and along with other mechanistic investigations, a plausible mechanism of the reaction was proposed.     

Efficient iodine catalyzed chemoselective synthesis of aminals—an access to N,N-acetals by the addition of lactams to N-acyl imines

A highly efficient protocol has been developed for the synthesis of aminals from γ-butyrolactam and benzaldehyde using iodine as Lewis acid catalyst. The attack of γ-butyrolactam nucleophile to intermediate N-acyliminium ion was more favorable, when aryl aldehyde bears the electron donating group (EDG). Iodine plays a key role in these reaction transformations. This current mild protocol is environmentally benign and cost-effective method for the synthesis of industrially and pharmaceutically useful scaffolds.     

N-Iodosuccinimide (NIS) as a mild and highly chemoselective catalyst for deprotection of tert-butyldimethylsilyl ethers

A variety of alcoholic TBDMS (t-butyldimethylsilyl) ethers are easily removed in excellent yields by treatment with a catalytic amount of N-iodosuccinimide (NIS, 5 mol %) in methanol. This method is able to deprotect TBDMS ethers of alcohols in the presence of TBDMS ethers of phenols.     

Asymmetric catalytic aziridination of dihydronaphthalenes for the preparation of substituted 2-aminotetralins

An enantioselective synthesis of substituted 2-aminotetralins from dihydronaphthalenes in four steps is described. The key step is the Jacobsen’s (diimine)copper-catalyzed asymmetric aziridination of dihydronaphthalenes to the respective aziridines in 33-82% yields and 60-87% enantiomeric excess. The enantioselectivity and the yield were dependent on the properties of the nitrene precursor. pTsNIPh appeared in general to give better results than pNsNIPh. Aziridines were ring-opened in the benzylic position by catalytic hydrogenolysis in quantitative yields, and deprotected in two steps to the respective 2-aminotetralins in 66-85% yields. The synthesis of (S)-2-aminotetralin (>98% ee) and (S)-2-amino-7-methoxytetralin (56% ee) were accomplished in 30 and 52% overall yields, respectively.     

An advantageous synthesis of new indazolone and pyrazolone derivatives

The synthesis of new indazolone and pyrazolone derivatives starting from methyl anthranilate type substrates is presented. This general approach constitutes a novel and advantageous alternative for the synthesis of the target heterocycles, which implies the use of the environmentally friendly oxidizer PIFA. The synthetic design includes the oxidation of N-arylamides by the hypervalent iodine reagent to the corresponding N-acylnitrenium ions, which can be intramolecularly trapped by an amine moiety to furnish the title compounds by formation of a new N-N single bond.     

A novel reagent combination for the oxidation of highly electron deficient pyridines to N-oxides: trifluoromethanesulfonic anhydride/sodium percarbonate

A novel reagent combination, Tf₂O/Na₂CO₃·1.5H₂O₂, has been developed for the oxidation of highly electron deficient pyridines to their corresponding N-oxides. The N-oxidation reaction, utilizing the in situ generated peracid, proceeds under mild conditions that allow for a number of functional groups and substitution patterns on the pyridine ring.     

Titanium superoxide: a heterogeneous catalyst for anti-Markovnikov aminobromination of olefins

A new facile procedure for the aminobromination of olefins in high yields has been described using p-toluene sulfonamide (p-TsNH₂) and N-bromosuccinimide (NBS) as nitrogen and bromine sources, respectively, and titanium superoxide as a truly heterogeneous catalyst. The formation of anti-Markovnikov product exclusively in all the cases studied possibly proceeding through a free radical reaction pathway is remarkable.     

The use of Nafion-H®/NaNO2 as an efficient procedure for the chemoselective N-nitrosation of secondary amines under mild and heterogeneous conditions

A combination of Nafion-H® and sodium nitrite in the presence of wet SiO₂ was used as an effective agent for the N-nitrosation of secondary amines under mild and heterogeneous conditions in good to excellent yields.     

Bromamine-T/RuCl3 as an efficient system for the oxidation of tertiary amines to N-oxides

A variety of tertiary amines were efficiently and selectively oxidized to the corresponding N-oxides by bromamine-T using ruthenium trichloride as catalyst in alkaline (pH 8.4) acetonitrile/water (1:1) at 80 °C.     

A highly efficient TEMPO mediated oxidation of sugar primary alcohols into uronic acids using 1-chloro-1,2-benziodoxol-3(1H)-one at room temperature

Oxidation of various sugar primary alcohols into corresponding uronic acids was demonstrated using 1-chloro-1,2-benziodoxol-3(1H)-one and TEMPO. The reaction proceeds at room temperature in good to excellent yields. Primary alcohols get oxidized selectively over the secondary alcohols under mild reaction conditions.     

N-Hydroxyphthalimide in combination with Cu(II), Co(II) or Mn(II) salts as catalytic systems for the oxidation of isopropyl-aromatic hydrocarbons with oxygen

Catalytic systems consisting of N-hydroxyphthalimide in combination with copper(II), cobalt(II) and manganese(II) acetylacetonate, acetate or chloride were applied to the oxidation of cumene with oxygen. The use of these catalytic systems decreases cumyl hydroperoxide selectivity as a result of the decomposition reaction of hydroperoxide to 2-phenyl-2-propanol and acetophenone. It has been demonstrated that the use of N-hydroxyphthalimide in combination with copper salts at 60 °C results in high alcohol content whereas ketone is the major product at 90 °C. The results can be used to develop a method for alcohol or ketone synthesis from other isopropyl-aromatic hydrocarbons.     

N-Bromosuccinimide-thiol cobromination in basic medium: an efficient one-pot transformation of olefins into the corresponding enol thioethers

A convenient method for the one-pot conversion of olefins into the corresponding enol thioethers is reported. The products were obtained via the N-bromosuccinimide cobromination reaction of olefins with thiols in basic medium. Steric hindrance present in the product alkenes may explain the stereochemistry observed.     

Facile generation of vicinal bromoazides from olefins using TMSN3 and TsNBr2 without any catalyst

A very rapid and efficient method has been developed for the synthesis of vicinal bromoazides directly from olefin using N,N-dibromo-p-toluenesulfonamide (TsNBr₂) without any catalyst. The reaction is extremely fast which goes into completion instantaneously to produce bromoazides. This procedure is applicable to various olefins such as cinnamates, chalcone, styrenes, and acrylate to give the corresponding 1,2-bromoazide in an excellent yield.     

N-Acyltrifluoromethanesulfonamides as new chemoselective acylating agents for aliphatic and aromatic amines

This work describes advances in the study of the internal condensation of ammonium salts of N-acylsulfonamides. N-Acyltrifluoromethanesulfonamides show considerable advantages over the non fluorinated analogues by virtue of their higher reactivity and acidity. The reaction chemoselectivity has been investigated using a wide range of amines. The sensitivity of the reaction to steric and electronic effects confirms the potential application of these reagents in chemoselective acylation of polyamines.     

2-Cyanopyridazin-3(2H)-ones: effective and chemoselective electrophilic cyanating agents

2-Cyanopyridazin-3(2H)-ones are novel, effective, selective and electrophilic cyanating agents. A variety of amino, thiol and carbon nucleophiles are chemoselectively N-, S- or C-cyanated in excellent yield using 2-cyanopyridanzin-3(2H)-ones in water or tetrahydrofuran.