Synthesis of hetero- and carbocycles by nucleophilic substitution at sp carbon

Vinylic halides having alcohol, sulfonamide, active methine, and thiol moieties as nucleophiles cyclize to hetero- and carbocycles by intramolecular nucleophilic substitution at the sp² carbon centers. The density functional theory calculations suggest that the cyclization proceeds through S_N2-type substitution (the in-plane vinylic nucleophilic substitution, S_NVσ), when vinyl halides are substituted with oxygen, nitrogen, and carbon nucleophiles. The substitution with sulfur nucleophiles, in contrast, proceeds through both routes of S_NVσ and out-of-plane vinylic nucleophilic substitution (S_NVπ).     

Water-promoted unprecedented chemoselective nucleophilic substitution reactions of 1,4-quinones with oxygen nucleophiles in aqueous micelles

Unique nucleophilic substitution and addition reactions of nitrogen and sulfur nucleophiles with 1,4-quinones in aqueous suspension with amines and thiols have recently been demonstrated by us.² However, the reactivity of oxygen nucleophiles toward nucleophilic substitution compared to nitrogen and sulfur nucleophiles ‘on water’ is not facile. An unprecedented economical, green methodology approach using ordinary laundry detergent (LD; washing powder, 0.5 mol %, reusable)/SDS as surfactant ‘in water’ for nucleophilic substitution by oxygen nucleophiles in 1,4-quinones in excellent yields has been demonstrated.     

Synthesis and reactivity of trans-2-aryl-3-chloroazetidines

Several trans-2-aryl-3-chloroazetidines were synthesized in a stereoselective way by reduction of the corresponding β-lactams, which were formed by a Staudinger reaction using different benzaldimines and chloroketene. The resulting chloroazetidines proved to be excellent building blocks for the synthesis of different 3-substituted azetidines through nucleophilic substitution of the chlorine by different carbon, nitrogen, sulfur and oxygen nucleophiles in good to high yields. Since these substitution reactions took place with retention of stereochemistry, the intermediacy of bicyclic azonio[1.1.0]bicyclobutanes is proposed.     

The Efficiency of the Metal Catalysts in the Nucleophilic Substitution of Alcohols is Dependent on the Nucleophile and Not on the Electrophile

In this study, we investigate the effect of the electrophiles and the nucleophiles for eight catalysts in the catalytic S_N1 type substitution of alcohols with different degree of activation by sulfur‐, carbon‐, oxygen‐, and nitrogen‐centered nucleophiles. The catalysts do not show any general variance in efficiency or selectivity with respect to the alcohols and follow the trend of alcohol reactivity. However, when it comes to the nucleophile, the eight catalysts show general and specific variances in the efficiency and selectivity to perform the desired substitution. Interestingly, the selectivity of the alcohols to produce the desired substitution products was found to be independent of the electrophilicity of the generated carbocations but highly dependent on the ease of formation of the cation. Catalysts based on iron(III), bismuth(III), and gold(III) show higher conversions for S‐, C‐, and N‐centered nucleophiles, and Bi^III was the most efficient catalyst in all combinations. Catalysts based on rhenium(I) or rhenium(VII), palladium(II), and lanthanum(III) were the most efficient in performing the nucleophilic substitution on the various alcohols with the O‐centered nucleophiles. These catalysts generate the symmetrical ether as a by‐product from the reactions of S‐, C‐, and N‐centered nucleophiles as well, resulting in lower chemoselectivity.     

Allylic activation across an Ir–Sn heterobimetallic catalyst: nucleophilic substitution and disproportionation of allylic alcohol

A nucleophilic substitution of allylic alcohols with carbon (arene, heteroarene, allyltrimethylsilane, and 1,3-dicarbonyl compound), sulfur (thiol), oxygen (alcohol), and nitrogen (sulfonamide) nucleophiles has been demonstrated using an in house developed [Ir(COD)(SnCl₃)l(μ-Cl)]₂ heterobimetallic catalyst in 1,2-dichloroethane to afford the corresponding allylic products in moderate to excellent yields. In 4-hydroxycoumarin, allylation occurs at the 3-position. The diaryl-substituted allylic alcohols undergo disproportionation in presence of the heterobimetallic catalyst to provide the corresponding alkenes and chalcones. An electrophilic mechanism is proposed from Hammett correlation study.     

Dynamic resolution of α-halo carboxylic acid derivatives in asymmetric nucleophilic substitution using chiral auxiliaries

Recent results on the chiral auxiliary-mediated dynamic resolution of α-halo acid derivatives in nucleophilic substitution have been outlined and classified into two major mechanistic categories, dynamic thermodynamic resolution (DTR) and dynamic kinetic resolution (DKR). Asymmetric nucleophilic substitution of α-halo acid derivatives with various nitrogen, oxygen, sulfur, and carbon nucleophiles is widely used for the stereoselective preparation of α-substituted carboxylic acids.     

Ortho-selective nucleophilic aromatic substitution reactions of polyhaloanilines with potassium/sodium o-ethyl xanthate: a convenient access to halogenated 2(3H)-benzothiazolethiones

Polyhaloanilines bearing an ortho halogen atom undergo smooth nucleophilic aromatic substitution reactions with anionic sulfur nucleophiles at relatively mild temperatures (95-120 degrees C). These reactions are very efficient and highly ortho-selective. With potassium/sodium O-ethyl xanthate as a nucleophile, subsequent cyclization follows to afford halogenated 2(3H)-benzothiazolethiones (2-mercaptobenzothiazoles) in high yields.     

Synthesis of substituted uracils by the reactions of halouracils with selenium, sulfur, oxygen and nitrogen nucleophiles under focused microwave irradiation

Under microwave irradiation, the nucleophilic substitution reactions of halouracils with selenium, sulfur, oxygen and nitrogen nucleophiles was complete within several minutes with yields up to 99%. The method using microwave irradiation is superior to those conducted under conventional heating processes.     

SILICON-PHOSPHORUS ANALOGIES THE MECHANISM OF NUCLEOPHILIC SUBSTITUTION AT SILICON AND PHOSPHORUS ACTIVATED BY EXTERNAL NUCLEOPHILES EXTENSION OF COORDINATION OF THE REACTIVE SPECIES

Abstract

A comparison is made concerning the mechanism of S_N2 reactions of silicon and phosphorus compounds, catalyzed by nucleophiles. The rate-law of the catalyzed solvolysis of halogenophosphorus esters corresponds to a mechanism with extension of coordination of the reactive species. The overall inversion observed with chlorophosphonates affords a distinction between a nucleophilic activated substitution S_NA (P) and a nucleophilic double displacement at phosphorus.     

Regiochemistry of nucleophilic substitution of 4-phenylsulfonyl tetrafluoropyridine with unequal bidentate nucleophiles

The regiochemistry of nucleophilic substitution of 4-phenylsulfonyl tetrafluoropyridine with unequal bidentate nucleophiles was investigated. The first nucleophilic substitution occurs at the 2-position of the pyridine ring by nitrogen nucleophile site (secondary or primary amine) followed by intermolecular ring closure at the geometrically accessible 3-position of the pyridine ring (by S, O and N nucleophiles). From this investigation, difluorinated tetrahydropyrido[3,4-b][1,4]oxazine, thiazine and pyrazine scaffolds were synthesized very readily by a one-pot annelation reaction of 4-phenylsulfonyl tetrafluoropyridine with appropriate unequal bidentate nucleophiles.     

Synthesis of Aryl 3,5-Dinitrophenyl Sulfones and Sulfoxides. Transformations of 3,5-Dinitrodiphenyl Sulfone in Reactions with O- and S-Nucleophiles

1-Arylthio-3,5-dinitrobenzenes are selectively oxidized to the corresponding sulfones and sulfoxides by the action of hydrogen peroxide. Reactions of 3,5-dinitrodiphenyl sulfone with O- and S-centered nucleophiles (RXH, X = O, S) in dipolar aprotic solvents in the presence of K₂CO₃ result in replacement of the nitro group by the RX fragment; the reaction with methanol occurs in aqueous medium in the presence of NaHCO₃. Substitution of the nitro group in 3,5-dinitrodiphenyl sulfone by phenylthio group, followed by oxidation of the sulfur atom to SO₂ and further replacement of the remaining nitro group yields 1,3,5-tris(phenylsulfonyl)benzene. The phenylsulfonyl group in the latter is replaced by phenylthio group by reaction with PhSH in the presence of K₂CO₃. Mononitrosulfones obtained by nucleophilic substitution in the title compound can be reduced to the corresponding anilines.     

Bifluoride Ion Mediated SuFEx Trifluoromethylation of Sulfonyl Fluorides and Iminosulfur Oxydifluorides

SuFEx is a new‐generation click chemistry transformation that exploits the unique properties of S?F bonds and their ability to undergo near‐perfect reactions with nucleophiles. We report here the first SuFEx‐based procedure for the efficient synthesis of pharmaceutically important triflones and bis(trifluoromethyl)sulfur oxyimines from sulfonyl fluorides and iminosulfur oxydifluorides, respectively. The new process involves rapid S?F exchange with trifluoromethyltrimethylsilane (TMSCF₃) upon activation by potassium bifluoride in anhydrous DMSO. The reaction tolerates a wide selection of substrates and proceeds under mild conditions without need for chromatographic purification. A tentative mechanism is proposed involving nucleophilic displacement of S?F by the trifluoromethyl anion via a five‐coordinate intermediate. The utility of late‐stage SuFEx trifluoromethylation is demonstrated through the synthesis and selective anticancer properties of a bis(trifluoromethyl)sulfur oxyimine.     

Novel Nucleophilic Substitution Reactions of 5‐Halo‐4‐Sulfur‐Substituted 5,6‐Dihydro‐2‐Pyridones

The title compounds ( 3 , 8 , 9 and 10 ) were efficiently synthesized, and their substitution reactions with various nucleophiles were carried out. The effects of leaving group, sulfur‐substituent, solvent, reaction temperature, and the nature of the nucleophiles on the reactivity and S_N2/S_N2′ regioselectivity were studied and rationalized with semi‐empirical calculations.     

Al(OTf)3: an efficient recyclable catalyst for direct nucleophilic substitution of the hydroxy group of propargylic alcohols with carbon- and heteroatom-centered nucleophiles to construct C-C, C-O, C-N and C-S bonds

A general and highly efficient Al(OTf)₃-catalyzed methodology has been developed for the direct nucleophilic substitution of the hydroxy group in propargylic alcohols with a variety of carbon- and heteroatom-centered nucleophiles such as alcohols, aromatic compounds, amides, and thiols, leading to the construction of C-C, C-O, C-N and C-S bonds.     

Spectroscopic and structural aspects of the reactions of 1,4-quinones with sulfur and nitrogen nucleophiles

A series of 1,4-benzoquinone derivatives from 2,5-dichloro-3,6-diethoxy-1,4-benzoquinone and 2,6-dichloro-3,5-diethoxy-1,4-benzoquinone were prepared by nucleophilic substitution reactions of sulfur and nitrogen nucleophiles. Spectral techniques (¹H NMR, ¹³C NMR, FT–IR, and LC–MS) were employed to structurally characterize the reaction products of alkoxy, chloro substituted-1,4-benzoquinones with thiols and amines in the presence of sodium carbonate in ethanol at room temperature. The orientations and the regioselectivity of the reactions of alkoxy, chloro substituted-1,4-benzoquinones with various thiol and amine nucleophiles are discussed.     

Al(OTf)3 as a new efficient catalyst for the direct nucleophilic substitution of ferrocenyl alcohol substrates. Convenient preparation of ferrocenyl-PEG compounds

The use of Al(OTf)₃ as a new efficient catalyst for the direct nucleophilic substitution of the hydroxy group of ferrocenyl alcohols is described. This catalyst, originally developed for the mono-substitution of ethylene glycol nucleophiles of different length has shown a high activity with other carbon-, nitrogen-, and sulfur-based nucleophiles. In all the studied cases, no more than 1 mol % of catalyst was needed to allow fast and clean reactions.     

Aromatic Nucleophilic Substitution. Part 1. Regiospecific Substitution of the Nitro Groups in 3,5-Dinitrophthalic-Acid Derivatives

The regioselectivity of nucleophilic substitution of the nitro groups in 3,5-dinitrophthalic anhydrides and 3,5-dinitrophthalimides (Scheme) with a variety of nucleophiles (Nu^?) was studied. In all cases, the 3-nitro group was selectively substituted. With excess of the same nucleophilic reagent or with other nucleophiles, the 5-nitro group could subsequently be replaced.     

全氟和多氟烷基磺酸的研究 XI: 全氟3-氧杂戊磺酸全氟苯酯的合成及其和亲核试剂的反应

Pentafluorophenyl and p-chlorotetrafluorophenyl-3- oxaperfluoroalkanesulfonates XCF2CF2OCF2CF2SO3C6F4Y (1) (Y=F, p-Cl) were synthesized by the reaction of 3-oxaperfluoroalkanesulfonyl fluoride with the corresponding sodium phenoxide in good yield. 1 reacted with various nucleophilic reagents more readily than phenyl perfluoroalkanesulfonates. The reactivity of nucleophiles toward 1 is parallel to the pKa values of their corresponding acids. All nucleophiles used (except C6H5S^-) attacked sulfur of 1 giving RfSO2Nu. Treatment of 1 with CH3CO^-2 produced perfluorophenyl acetate. When equivalent amount of KF was added to the reaction mixture the yield of the acetate decreased and main product was acetyl fluoride. This showed that the reaction followed the course of intermediary mixed anhydride formed through the attack of CH3CO^-2 on sulfur of 1. But when 1 was treated with ArS^- the only reaction occurred was C-O scission of the sulfenate by the nucleophilic attack of ArS^- on the fluorinated benzene ring to give the totrasubstituted perfluorobenzene, 1, 2, 4, 5-C6F2 (SAr)4. In contrast to the nucleophilic reaction of the mono-substituted pentafluorobenzene it was shown that in all reactions with nucleophiles para or ortho di-substituted compounds such as ReSO3C6F4Nu were not found.     

Some nucleophilic substitutions in 2‐cyano‐3‐nitroimidazo[1,2‐a]pyridine

In some nucleophilic substitution reactions of 2‐cyano‐3‐nitroimidazo[1,2‐a]pyridine, nitrogen (alkylamines, guanidine) and oxygen nucleophiles (alkoxides) underwent substitution of the 2‐cyano group, while sulfur nucleophiles (alkylthiols) underwent substitution of the 3‐nitro group.