Aromatic Nucleophiles Research Articles

ChemInform Abstract: Catalytic, Enantioselective, Intramolecular Carbosulfenylation of Olefins. Preparative and Stereochemical Aspects.

The first catalytic, enantioselective, intramolecular carbosulfenylation of isolated alkenes with aromatic nucleophiles is described. The combination of N-phenylsulfenylphthalimide, a chiral selenophosphoramide derived from BINAM, and ethanesulfonic acid as a cocatalytic Bronsted acid induced an efficient and selective cyclofunctionalization of various alkenes (aliphatic and aromatic) tethered to a 3,4-methylenedioxyphenyl ring. Under these conditions, 6-phenylthio-5,6,7,8-tetrahydronaphthalenes are formed diastereospecifically in good yields (50–92%) and high enantioselectivities (71:29–97:3 er). E-Alkenes reacted much more rapidly and with much higher selectivity than Z-alkenes, whereas electron-rich alkenes reacted more rapidly but with comparable selectivity to electron-neutral alkenes and electron-deficient alkenes. The Bronsted acid played a critical role in effecting reproducible enantioselectivity. A model for the origin of enantioselectivity and the dependence of rate and selectivity on alkene st...

Urea-catalyzed N-H insertion-arylation reactions of nitrodiazoesters.

The power of hydrogen-bond donor catalysis has been harnessed to elicit and control carbene-like reactivity from nitrodiazoesters. Specifically, select ureas have been identified as effective catalysts for N-H insertion and multicomponent coupling reactions of nitrodiazoesters, anilines, and aromatic nucleophiles, thereby preparing a variety of α-aryl glycines in high yield. Experimental and computational studies designed to probe the plausible reaction pathways suggest that difluoroboronate ureas are particularly well-suited to catalyze reactions of nitrodiazoesters with a range of anilines through a polar reaction pathway. Urea-facilitated loss of nitrite followed by addition of a nucleophile conceivably generates the observed aryl glycine products.

Type 1 Ring-Opening Reactions of Cyclopropanated 7-Oxabenzonorbornadienes with Organocuprates

For the first time, nucleophilic ring-openings of cyclopropanated 7-oxabenzonorbornadiene were investigated, providing a novel approach to the preparation of 2-methyl-1,2-dihydronaphthalen-1-ols. Satisfactory yields (up to 95%) were achieved using n-Bu2CuCNLi2 as the nucleophile and Et2O as the solvent. The reaction demonstrated successful incorporation of primary, secondary, tertiary and aromatic nucleophiles, as well as ring-openings of substrates bearing arene substituents and C1-bridgehead substituents. A generalized mechanism for these transformations is also proposed.

NIS‐Assisted Aza‐Friedel–Crafts Reaction with α‐Carbamoysulfides as Precursors of N‐Carbamoylimines

A general and practical N-iodosuccinimide (NIS)-promoted aza-Friedel-Crafts reaction of various aromatic nucleophiles with N-acylimines generated in situ from α-amidosulfides to give a rapid access to highly functionalized amines is described. The newly developed methodology is very mild, fast, efficient, and complementary.

4‐(Pentafluorosulfanyl)benzenediazonium Tetrafluoroborate: A Versatile Launch Pad for the Synthesis of Aromatic SF5 Compounds via Cross Coupling, Azo Coupling, Homocoupling, Dediazoniation, and Click Chemistry

AbstractThe reagent 4‐(pentafluorosulfanyl)benzenediazonium tetrafluoroborate (1) was synthesized and isolated as a stable salt for the first time; its application in a wide assortment of transformations was subsequently investigated. A series of novel SF5‐bearing alkenes, alkynes, and biaryl derivatives were synthesized by employing Heck–Matsuda, Sonogashira, and Suzuki coupling protocols. Dediazoniation with TMSX (X = Hal; N3; and CN) and NH4SCN in [BMIM][BF4] as solvent furnished the corresponding p‐SF5–C6H4X derivatives. The azide derivative p‐SF5–C6H4N3 entered into click chemistry with phenylacetylenes to furnish the corresponding triazoles. The 4,4′‐bis(pentafluorosulfanyl)biphenyl was synthesized by homo‐coupling using Pd(OAc)2. The corresponding azo compounds were obtained through azo‐coupling with reactive aromatic nucleophiles (1,3‐dimethoxybenzene, 1,3,5‐trimethoxybenzene, 1,2,4‐trimethoxybenzene, aniline and phenol). Fluorodediazoniation in [BMIM][PF6] and [BMIM][BF4] selectively furnished the fluoro derivative p‐SF5–C6H4F. Dediazoniation in [BMIM][NTf2] gave p‐SF5–C6H4OS(O)(CF3)=NSO2CF3 as the major and p‐SF5–C6H4‐NTf2 as the minor products. Homolytic dediazoniation in MeCN/NaI gave the unsymmetrical biaryls p‐SF5–C6H4‐Ar (ArH = mesitylene and p‐xylene) along with p‐SF5–C6H4I. Analysis of the dediazoniation product mixtures indicated that dediazoniation of p‐SF5–C6H4N2+ BF4– in low nucleophilicity, highly ionizing, solvents (TfOH, TFE, HFIP, TFAH) is mainly heterolytic, while in MeOH it is mainly homolytic. The isodesmic reaction p‐SF5–C6H4+ + R‐C6H5 → SF5–C6H5 + p‐R‐C6H4+ (with R = NO2, CF3, H) was gauged by DFT at various levels and by PCM.

Facile synthesis of 5H-benzo[b]carbazol-6-yl ketones via sequential reaction of Cu-catalyzed Friedel-Crafts alkylation, iodine-promoted cyclization, nucleophilic substitution and aromatization.

A convenient method to access 5H-benzo[b]carbazol-6-yl ketones via a sequential Cu-catalyzed Friedel-Crafts alkylation reaction of indoles with 2-(2-(alkynyl)benzylidene)malonates and iodine-promoted electrophilic cyclization followed by nucleophilic substitution and aromatization was developed. The products of the functional 5H-benzo[b]carbazol-6-yl ketones were obtained with up to 98% yield.

Catalytic, enantioselective, intramolecular carbosulfenylation of olefins. Preparative and stereochemical aspects.

The first catalytic, enantioselective, intramolecular carbosulfenylation of isolated alkenes with aromatic nucleophiles is described. The combination of N-phenylsulfenylphthalimide, a chiral selenophosphoramide derived from BINAM, and ethanesulfonic acid as a cocatalytic Brønsted acid induced an efficient and selective cyclofunctionalization of various alkenes (aliphatic and aromatic) tethered to a 3,4-methylenedioxyphenyl ring. Under these conditions, 6-phenylthio-5,6,7,8-tetrahydronaphthalenes are formed diastereospecifically in good yields (50-92%) and high enantioselectivities (71:29-97:3 er). E-Alkenes reacted much more rapidly and with much higher selectivity than Z-alkenes, whereas electron-rich alkenes reacted more rapidly but with comparable selectivity to electron-neutral alkenes and electron-deficient alkenes. The Brønsted acid played a critical role in effecting reproducible enantioselectivity. A model for the origin of enantioselectivity and the dependence of rate and selectivity on alkene structure is proposed along with a rationale for the site selectivity in reactions with monoactivated arene nucleophiles.

ChemInform Abstract: The Disubstitution of Acetals to Prepare δ,δ‐Bis(aryl) β‐Keto Esters.

An efficient catalytic protocol for the synthesis of δ,δ-bis(aryl)-substituted β-keto esters has been developed. This method involves the Lewis acid catalysed disubstitution reaction of ester-substituted silyl enol ether acetals with a series of aromatic nucleophiles to afford valuable functionalized β-keto esters with several sites available for further derivatisation.

Fast Controlled Living Polymerization of Arylisocyanide Initiated by Aromatic Nucleophile Adduct of Nickel Isocyanide Complex.

The fast living polymerization of chiral arylisocyanide in the presence of the aromatic nucleophile adduct of tetra(t-butylisocyano)nickel(II) complex as an initiator gave the predominantly one-handed helical polyisocyanide with narrow polydispersity. X-ray crystal structures of initiators and MALDI-TOF MS and NMR studies of the polymer products elucidated the key role of the aromatic substituents in the initiator and monomer achieving narrow polydispersity. The aromatic groups in the initiator and monomer stabilized the electronic structure of the carbene-like ligand to suppress dissociation of the active nickel complex that leads to chain transfer and termination. The aromatic groups also controlled the reactivity of the active site for initiation and propagation.

ChemInform Abstract: Catalytic, Enantioselective, Intramolecular Carbosulfenylation of Olefins.

AbstractFor the first time a catalytic enantioselective carbosulfenylation of alkenes with an aromatic nucleophile is presented.

The Disubstitution of Acetals to Prepare δ,δ‐Bis(aryl) β‐Keto Esters

AbstractAn efficient catalytic protocol for the synthesis of δ,δ‐bis(aryl)‐substituted β‐keto esters has been developed. This method involves the Lewis acid catalysed disubstitution reaction of ester‐substituted silyl enol ether acetals with a series of aromatic nucleophiles to afford valuable functionalized β‐keto esters with several sites available for further derivatisation.

Catalytic, Enantioselective, Intramolecular Carbosulfenylation of Olefins

The first catalytic, enantioselective carbosulfenylation of alkenes with an aromatic nucleophile is described, using a BINAM-based selenophosphoramide catalyst. E-Alkyl- and aryl-substituted alkenes afforded tetrahydronaphthalenes with complete diastereospecificity, and generally high enantiomeric ratios.

Enantioselective Formal Synthesis of (−)-Podophyllotoxin from (2S,3R)-3-Arylaziridine-2-carboxylate

Meyers' 4-aryl-1-tetralone-lactone and ent-Zhang's 2-diarylmethyl-4-oxobutanoate were synthesized in the formal synthesis of (-)-podophyllotoxin from (2S,3R)-3-arylaziridine-2-carboxylate, via 3,3-diarylpropanoate as a common intermediate, in an overall 42% yield through 10 steps and 31% yield through 6 steps, respectively. The key steps in the synthesis were regio- and diastereoselective ring opening with an aromatic nucleophile, samarium iodide promoted reductive C-N bond cleavage, and Stille coupling for introducing the vinyl functionality. The starting aziridine was enantioselectively prepared from 3,4,5-trimethoxybenzaldehyde by guanidinium ylide mediated asymmetric aziridination. All nitrogen components used in the reaction sequence are reusable as the starting guanidinium source.

Nucleophile‐Directed Selective Transformation of cis‐1‐Tosyl‐2‐tosyloxymethyl‐3‐(trifluoromethyl)aziridine into Aziridines, Azetidines, and Benzo‐Fused Dithianes, Oxathianes, Dioxanes, and (Thio)morpholines

A five-step procedure for the synthesis of cis-1-tosyl-2-tosyloxymethyl-3-(trifluoromethyl)aziridine was developed, starting from 1-ethoxy-2,2,2-trifluoroethanol, involving imination, aziridination, ester reduction, hydrogenation, and N-,O-ditosylation steps. Further synthetic elaborations revealed a remarkable difference in the reactivity of cis-1-tosyl-2-tosyloxymethyl-3-(trifluoromethyl)aziridine with respect to aromatic sulfur and oxygen nucleophiles, thus enabling the selective deployment of this versatile substrate as a building block for the synthesis of functionalized aziridines, azetidines, and benzo-fused dithianes, oxathianes, dioxanes, and (thio)morpholines.

Assessing the regioselectivity of OleD-catalyzed glycosylation with a diverse set of acceptors.

To explore the acceptor regioselectivity of OleD-catalyzed glucosylation, the products of OleD-catalyzed reactions with six structurally diverse acceptors flavones- (daidzein), isoflavones (flavopiridol), stilbenes (resveratrol), indole alkaloids (10-hydroxycamptothecin), and steroids (2-methoxyestradiol)-were determined. This study highlights the first synthesis of flavopiridol and 2-methoxyestradiol glucosides and confirms the ability of OleD to glucosylate both aromatic and aliphatic nucleophiles. In all cases, molecular dynamics simulations were consistent with the determined product distribution and suggest the potential to develop a virtual screening model to identify additional OleD substrates.

Friedel–Crafts Ring-Coupling Reactions Promoted by Tungsten Dearomatization Agent

The complexes TpW(NO)(PMe3)(L), where L = phenol, N,N-dimethylanilinium, or naphthalene, undergo protonation followed by addition of an aromatic nucleophile. The addition of aromatic molecules occurs at the para carbon of the phenol or aniline ring or the beta carbon of the naphthalene. The addition occurs anti to the metal fragment, as determined by X-ray crystallography. In the case where L = phenol or N,N-dimethylanilinium, treatment of the bound arene with an electrophilic heteroatom followed by an aromatic nucleophile sets two stereocenters, with both additions occurring anti to the metal. The resultant ligands have been removed from the metal by oxidative decomplexation using ceric ammonium nitrate.

FeCl3‐Mediated Friedel–Crafts Hydroarylation with Electrophilic N‐Acetyl Indoles for the Synthesis of Benzofuroindolines

IRONic electrophilic indoles! The C3-regioselective hydroarylation of N-acetyl indoles with aromatic nucleophiles mediated by FeCl(3) features a rare example of the electrophilic reactivity of the indole core in a Friedel-Crafts reaction. This indole umpolung allows us straightforward access to the tetracyclic benzofuroindoline motif found in the natural product diazonamide A, which is a potent antitumor agent.

FeCl3‐Mediated Friedel–Crafts Hydroarylation with Electrophilic N‐Acetyl Indoles for the Synthesis of Benzofuroindolines

IRONic electrophilic indoles! The C3-regioselective hydroarylation of N-acetyl indoles with aromatic nucleophiles mediated by FeCl(3) features a rare example of the electrophilic reactivity of the indole core in a Friedel-Crafts reaction. This indole umpolung allows us straightforward access to the tetracyclic benzofuroindoline motif found in the natural product diazonamide A, which is a potent antitumor agent.

Quaternary Chiral β2,2-Amino Acids with Pyridinium and Imidazolium Substituents

The reactions of cyclic sulfamidates as electrophiles with a variety of nitrogen-containing aromatic heterocycle nucleophiles, such as pyridines, N-alkylimidazoles and N-methylbenzimidazol, was explored. In all cases, although the nucleophilic substitution reactions occurred on quaternary centres, elimination products were not detected. The inversion of configuration at this quaternary centre was determined by X-ray diffraction analysis and the enantiomeric excess of the reactions was checked by chiral HPLC. This synthetic approach allowed us to obtain a new family of chiral charged β(2,2)-amino acids, including a new bisamino acid that incorporates an imidazolium salt as a cross-linker. In this context, the treatment of these chiral imidazolium salts with Ag(2)O opens the way to new chiral N-heterocyclic carbenes, which are important substrates in the fields of organometallic and organocatalytic chemistry. Additionally, we have done a thorough conformational analysis of these β-amino acid derivatives, both in the solid state and in solution. The most important conformational feature of these acyclic systems is the rigidity of the N-CH(2)-C-N(+) dihedral angle, which is essentially due to the gauche effect.

ChemInform Abstract: Acid‐Promoted Rearrangement of Arylmethyl Azides: Applications Toward the Synthesis of N‐Arylmethyl Arenes and Polycyclic Heteroaromatic Compounds.

AbstractAcid‐promoted Aube—Schmidt rearrangement of arylmethyl azides provides an intermediary iminium ion which can be trapped by aromatic nucleophiles leading to N‐arylmethyl arenes and by heteroaromatic compounds lading to polyheterocyclic compounds.