N-sulfonyl Group Research Articles

Dearomatization of [2.2]Paracyclophane-Derived N-Sulfonylimines through Cyclopropanation with Sulfur Ylides.

An unprecedented dearomatization of [2.2]paracyclophane-derived cyclic N-sulfonylimines was conducted through cyclopropanation with sulfur ylides, giving a series of dearomative cyclopropanes with good yields. DFT calculations suggested that the dearomatization was attributed to the relatively weak aromaticity of [2.2]paracyclophane derivatives that resulted from the effect of the unique [2.2]paracyclophane skeleton and the electron-withdrawing N-sulfonyl group. Some downstream elaborations of the products were demonstrated.

Synthesis of 2,3-Disubstituted pyrroles by Lewis acid promoted cyclization of N-Sulfonyl vinylogous carbamates and amides

A three-step sequence to construct pyrroles from three components including 2,2-dimethoxyethylamine, aryl/alkyl sulfonyl chlorides and alkynes bearing electron-withdrawing groups is presented. The pyrroles are proposed to arise via a 5-exo-trig cyclization proceeding through both oxocarbenium and N-sulfonyliminium ions. This modular route allows for the variability at the N-sulfonyl group, the C2 and C3 substituents for rational vectoring of the pyrrole nucleus for downstream processes.

Ni(0)-Catalyzed Three-Component Coupling Reaction of Tetrafluoroethylene and N-Sulfonyl-Substituted Imines with Silanes via Aza-Nickelacycles.

A nickel-catalyzed three-component coupling reaction of tetrafluoroethylene (TFE) and N-sulfonyl-substituted imines with silanes that furnishes a variety of fluorine-containing amines is disclosed. Stoichiometric experiments revealed that the aza-nickelacycles generated upon oxidative cyclization of TFE and N-sulfonyl-substituted imines on Ni(0) were identified as the key intermediates in this catalytic reaction. A single-crystal X-ray diffraction analysis of such an aza-nickelacycle revealed that the O atom of the N-sulfonyl group stabilizes the key intermediate via coordination to the nickel center.

Catalyst-Free Synthesis of Aminals from Indole-Derived α,α-Di­cyanoolefins

We have developed an efficient synthesis of indole fused aminals with nucleophilic imines and indole-derived α,α-dicyanoolefins via N-sulfonyl group transfer. The combination of two privileged frameworks, tetrahydroisoquinoline or tetrahydro-β-carboline and indole, can be realized by this approach to the construction of aminals. The synthetic application of this method was further demonstrated by the straightforward transformations into highly functionalized aminals possessing carbonyl groups through oxidative cleavage of the nitrile moiety.

Highly regiocontrolled and stereocontrolled syntheses of polysubstituted aminocyclohexanes: mild inverse-electron-demand Diels–Alder cycloadditions of electrophilic 2-pyridones

Strongly electrophilic N-arenesulfonyl-2-pyridone-3-carboxylate methyl esters complex with zinc dibromide and then react with nucleophilic benzyl vinyl ether or benzyloxyallene to achieve inverse-electron-demand Diels–Alder (IEDDA) cycloadditions. These cycloadducts are produced on gram scale and in 77–89% yields, importantly without the use of high pressure. These 4+2 cycloadditions strongly favor regioselective and stereoselective formation of endo bicyclic lactams as established by X-ray crystallography. These bicyclic lactams undergo useful reactions, including reductive cleavage of the N-sulfonyl group, exo-syn-dihydroxylations, and lactam ring-opening to produce a variety of aminocyclitols.

Antiproliferative Evaluation of N-sulfonyl-2-alkyl-six Membered Azacycles. A QSAR Study

A series of functionalized N-sulfonyl-piperidines and N-sulfonyl-tetrahydropyridines were evaluated for their antiproliferative activity against the representative panel of human solid tumor cells A2780 (ovarian), SW1573 (non-small cell lung) and WiDr (colon). The SAR study showed for WiDr cells a correlation between the biological activity and the length of the N-sulfonyl group, the nature of the substituents and the type of alkyl side chain. Further QSAR studies indicate that the size and nature of the N-sulfonyl group, the atomic polarizability (MP) and the partition coefficient are the most important descriptors for the activity. The major contribution is the size (F05C-S) of the N-sulfonyl group.

N-benzoyl- and N-sulfonyl-1,5-benzodiazepines: comparison of their atropisomeric and conformational properties.

The atropisomeric and conformational properties of 1,5-benzodiazepines with an N-sulfonyl (p-tosyl/mesyl) group (IIa/b) were investigated by comparison with those of the N-benzoyl congeners (I). Similar to I, when the Ar-N(SO2) axis was frozen by a C9-substitution in the molecules, IIa/b were separated into the (aR)- and (aS)-atropisomers. The conformation of IIa/b revealed that the substituent (p-tolyl/methyl group) in the sulfonyl moiety occupies the position over the diazepine ring (folded form) in both the solid and solution states [e.g., (+)-(aR)-N-p-tosyl-1,5-benzodiazepin-2-one (IIa-2)], whereas that of I is anti to the diazepine ring [e.g., (-)-(aR)-N-benzoyl-1,5-benzodiazepin-2-one (I-2)], which was further supported by a computational study. The stereochemical stability also differed between the two congeners (e.g., ΔG(‡): 104 kJ/mol for I-2 and 132 kJ/mol for IIa-2).

Isothiourea‐Mediated One‐Pot Synthesis of Functionalized Pyridines

Isothiourea‐Mediated One‐Pot Synthesis of Functionalized Pyridines

Mechanistic analysis and optimization of the copper-catalyzed enantioselective intramolecular alkene aminooxygenation.

The catalytic asymmetric aminooxygenation of alkenes provides an efficient and straightforward approach to prepare chiral vicinal amino alcohols. We have reported a copper(II)-catalyzed enantioselective intramolecular alkene aminooxygenation, using (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) as the oxygen source, which results in the synthesis of chiral indolines and pyrrolidines. Herein we disclose that kinetics studies indicate the reaction is first order both in substrate and the [Cu(R,R)-Ph-bis(oxazoline)]OTf(2) catalyst and zero order in TEMPO. Furthermore, kinetic isotope effect studies support that the cis-aminocupration step, the addition of N-Cu across the alkene, is the rate-limiting step. Subsequent formation of a carbon radical intermediate and direct carbon radical trapping with TEMPO is the indicated mechanism for the C-O bond formation as suggested by a deuterium labeling experiment. A ligand screen revealed that C(4)-phenyl substitution on the bis(oxazoline) is optimal for high asymmetric induction. The size of the substrate's N-sulfonyl group also influences the enantioselectivity of the reaction. The preparative-scale catalytic aminooxygenation reaction (gram scale) was demonstrated, and an unexpected dependence on reaction temperature was uncovered on the larger scale reaction.

Synthesis of Enaminones by Rhodium-Catalyzed Denitrogenative Rearrangement of 1-(N-Sulfonyl-1,2,3-triazol-4-yl)alkanols

Enaminones are synthesized by the rhodium(II)-catalyzed denitrogenative rearrangement reaction of 1-(N-sulfonyl-1,2,3-triazol-4-yl)alkanols, which are readily prepared from propargylic alcohols and N-sulfonyl azides. Intramolecular 1,2-hydride (or -alkyl) migration occurs with an intermediary α-imino rhodium(II) carbenoid species generated through denitrogenation of the 1,2,3-triazol-4-yl moiety. The resulting enaminones is converted into various heterocycles with replacement of the N-sulfonyl group.

Furan ring opening–indole ring closure: recyclization of 2-(2-aminophenyl)furans into 2-(2-oxoalkyl)indoles

The acid-catalyzed rearrangement of 5-alkyl-2-[2-(sulfonylamino)phenyl]furans into 2-(2-oxoalkyl)indoles is described. When the N-sulfonyl group in the starting compounds was displaced by an N-acyl group, the corresponding indoles were not formed under the same reaction conditions due to the in situ indole deacylation and decomposition. The presence of an alkyl group at the C5 position of the furan ring is also crucial for the efficiency of the process. The discussed rearrangement provides a simple and efficient approach to 2-(2-oxoalkyl)indoles.

Synthesis of Dihydroquinolones Using a Bifunctional Thiourea Catalyst

Lu and co-worker reported an ­intramolecular cyclization of activated anilines onto ester-substituted unsaturated ketones using bifunctional thiourea catalyst 1, leading to bioactive quinolone derivatives. The products were obtained in generally good yields and high enantio­selectivities. The target quinolones were obtained without loss of enantiopurity after removing the N-sulfonyl group.

ChemInform Abstract: Broadening the Synthetic Scope of the Iron(III)‐Catalyzed Aza‐Prins Cyclization.

AbstractRing formation proceeds equally well for the N‐nosyl and N‐mesyl substrates.

Stereoselective synthesis of N,N-acetals by cyclization of an N-acyliminium ion through interaction with an N-sulfonyl group

A new method for the stereoselective synthesis of five- and six-membered bicyclic N,N-acetals with trans configuration was developed using N-acyliminium ion cyclization. The N-sulfonyl substituted compounds were effectively cyclized to give the corresponding acetals in high yields and stereoselectivities, suggesting that the intramolecular interaction between the iminium and the sulfonyl group plays a key role in the cyclization.

Construction of Robust Ruthenium(salen)(CO) Complexes and Asymmetric Aziridination with Nitrene Precursors in the Form of Azide Compounds That Bear Easily Removable N‐Sulfonyl Groups

We synthesized new Ru(salen)(CO) complexes of high durability and achieved aziridination with good to excellent enantioselectivity by using azide compounds that contain an easily removable N-sulfonyl group, such as the 2-(trimethylsilyl)ethanesulfonyl group, as a nitrene precursor. Aziridination of less-reactive alpha,beta-unsaturated esters (and amides) proceeded with excellent enantioselectivities, from which it is inferred that an electrophilic species is the active species of this reaction. The present asymmetric aziridination provides a useful tool for introducing optically active nonprotected amine groups.

Mechanism and Diastereoselectivity of Aziridine Formation from Sulfur Ylides and Imines: A Computational Study

A computational investigation of the title reaction involving semistabilized (R = Ph) and stabilized (R = CO2Me) sulfur ylides has been performed using DFT methods including a continuum model of solvent. Our results provide support for the generally accepted mechanism and are in very good agreement with observed cis/trans selectivities. This study shows that betaine formation is nonreversible, and that selectivity is thereby determined at the initial addition step, in the case of semistabilized ylides. Our analysis indicates moreover that addition TS structures are governed by the steric strain induced by the N-sulfonyl group, which favors the transoid approach in the case of syn betaine formation and the cisoid mode of addition in anti TSs. The observed low trans selectivity is accounted for by the favorable Coulombic interactions and stabilization by C-H...O hydrogen bonding allowed in the cisoid anti addition TS. In the case of stabilized ylides, the endothermicity of betaine formation combined with the high barrier to ring closure render the elimination step rate- and selectivity-determining. Accordingly, the low cis selectivity observed in stabilized ylide reactions is explained by the lower steric strain in the elimination step generated by the formation of the cis aziridine (as compared to the trans case).

Indolecarbonyl Coupling Reactions Promoted by Samarium Diiodide. Application to the Synthesis of Indole-Fused Compounds

By the assistance of an N-sulfonyl group or a cyano group at the C-2 position, hydroxyalkylations of indole-3-carbonyls were achieved by the promotion of samarium diiodide. The indolecarbonyl coupling reactions proceeded in high stereoselectivity via chelate transition states. Intramolecular indolecarbonyl couplings of 1-(3-oxopropyl)indole-3-carboxaldehydes were realized as the indolecarbonyl group was more reactive toward SmI2 than the aliphatic carbonyl group. Elaboration of the coupling products with oxidizing agents, acid, phosphorus pentasulfide (or Lawesson's reagent), amines, and hydrazine led to a variety of indole derivatives and indole-fused polycyclic compounds of synthetic interest and pharmaceutical uses.

N-Phenylsulfonyl-N-o-chlorophenylmethacrylamide, C16H14ClNO3S

N-Phenylsulfonyl-N-o-chlorophenylmethacrylamide was obtained as a by-product in the synthesis of N-o-chlorophenylmethacrylamide. The geometry of the amide group substituted by the N-sulfonyl group and the conformation around the S IV -N bond have been studied