全氟辛基磺酸稀土金属盐催化氟两相酯化反应

制备了全氟辛基磺酸稀土金属盐[RE(OSO₂C₈F₁₇)₃, RE＝Sc, Y, La～Lu]并研究了该催化剂作用下氟两相酯化反应. 全氟己烷(C₆F₁₄)、全氟甲苯(C₇F₈)、全氟甲基环己烷(C₇F₁₄)、全氟辛烷(C₈F₁₈)、1-溴代全氟辛烷(C₈F₁₇Br)和全氟萘烷(C₁₀F₁₈, 顺式与反式的混合物)可作为该反应的氟溶剂. 研究表明Yb(OSO₂C₈F₁₇)₃和C₁₀F₁₈分别是最好的氟代催化剂和氟溶剂. 以Yb(OSO₂C₈F₁₇)₃为催化剂在C₁₀F₁₈中苯甲酸和异戊醇的酯化反应得率为99%. 含有催化剂的氟相通过简单的相分离, 就可回收利用, 氟相重复使用5次, 其催化活性减少不大.     

Rare earth(III) perfluorooctanesulfonates catalyzed Friedel-Crafts alkylation in fluorous biphase system

The catalyst of rare earth(III) perfluorooctanesulfonates (RE(OSO₂C₈F₁₇)₃, RE = Sc, Y, La-Lu) were prepared from either rare earth chlorides(III) or oxides and perfluorooctanesulfonic acid. The perflates thus obtained act as novel catalysts for Friedel-Crafts alkylation in fluorous biphasic system. Perfluorohexane (C₆F₁₄), perfluoromethylcyclohexane (C₇F₁₄), perfluorotoluene (C₇F₈), perfluorooctane (C₈F₁₈), perfluorooctyl bromide (C₈F₁₇Br) and perfluorodecalin (C₁₀F₁₈, cis- and trans-mixture) can be used as fluorous solvents for this reaction. By simple separation of the fluorous phase containing only catalyst, alkylation can be repeated many times.     

One-pot three components synthesis of O-acetylcyanohydrins with TMSCN, acetic anhydride and carbonyl compounds under solvent-free condition

One-pot three components synthesis of O-acetylcyanohydrins has been developed in the presence of B(C₆F₅)₃ as the catalyst. Variety of aldehydes or ketones reacts with TMSCN and acetic anhydride (Ac₂O) under the influence of 1 mol % of B(C₆F₅)₃ to give good to excellent yield of the products without solvent at rt.     

Heptadecafluorooctanesulfonic acid (C8F17SO3H) catalyzed intramolecular hydroamination of olefinic sulfonamides in fluorous biphase system (FBS)

A practical, efficient, and environmentally benign intramolecular hydroamination of olefinic sulfonamides was carried out in fluorous biphase system (FBS) using commercially available heptadecafluorooctanesulfonic acid (C₈F₁₇SO₃H) as a catalyst and perfluorodecaline (C₁₀F₁₈, cis- and trans- mixture) as a fluorous solvent to produce the corresponding cyclic products in good yields. The Brønsted acid of C₈F₁₇SO₃H is easily recovered and recycled at least five times.     

Recyclable hafnium(IV) bis(perfluorooctanesulfonyl)amide complex for catalytic Friedel-Crafts acylation and Prins reaction in fluorous biphase system

In fluorous biphase system, hafnium(IV) bis(perfluorooctanesulfonyl)amide complex (Hf[N(SO₂C₈F₁₇)₂]₄) was found to be a highly reactive and recyclable Lewis acid catalyst for Friedel-Crafts acylation and Prins reaction at significantly low catalyst loadings (≤1 mol%). In these reactions, Hf[N(SO₂C₈F₁₇)₂]₄ is selectively soluble in the lower fluorous phase and can be recovered simply by phase separation. Furthermore, the catalyst can be reused without decrease of activity.     

An efficient synthesis of 5-substituted 1H-tetrazoles via B(C6F5)3 catalyzed [3+2] cycloaddition of nitriles and sodium azide

A simple and efficient protocol is developed for the synthesis of 5-substituted 1H-tetrazole derivatives from various nitriles and sodium azide (NaN₃) via [3+2] cycloaddition reaction using B(C₆F₅)₃ as a catalyst. The present synthetic method displayed significant advantages such as low catalyst loading, mild reaction conditions, low toxicity, easy work-up, high yields, and compatibility with other functional groups.     

Hf[N(SO2C8F17)2]4-catalyzed Friedel-Crafts acylation in a fluorous biphase system

In a fluorous biphase system, Hf[N(SO₂C₈F₁₇)₂]₄ complex (1 mol %) catalyzes Friedel-Crafts acylation of aromatic compounds such as anisole, toluene and chlorobenzene, and the corresponding aromatic ketones are obtained in satisfactory to high yields. The catalyst is selectively soluble in lower fluorous phase and can be easily recovered by simple phase separation. Furthermore, the catalyst can be reused without decrease of activity in most cases.     

A novel fluorous palladium catalyst for Suzuki reaction in fluorous media

Palladium(II) perfluorooctanesulfonate [Pd(OSO₂R_f8)₂] catalyses the highly efficient Suzuki reaction in the presence of a catalytic amount of perfluoroalkylated-pyridine as a ligand in a fluorous biphase system (FBS). The fluorous phase containing the active palladium species is easily separated and can be reused several times without a significant loss of catalytic activity.     

Air-stable titanocene bis(perfluorooctanesulfonate) as a new catalyst for acylation of alcohols, phenols, thiols, and amines under solvent-free condition

Air-stable titanocene bis(perfluorooctanesulfonate) [Cp₂Ti(OSO₂C₈F₁₇)₂] that shows high Lewis acidity was prepared from Cp₂TiCl₂ and AgOSO₂C₈F₁₇. The compound was characterized by different techniques, and examined as a catalyst for acylation reactions. It was found that using equimolar acetic anhydride as acetylating agent and under solvent-free condition, Cp₂Ti(OSO₂C₈F₁₇)₂ exhibits high activity and selectivity in the acetylation of various alcohols, phenols, thiols, and amines. Also, good catalytic efficiency is observed in the acylation of 2-phenylethanol across various acylating reagents. The catalyst can be reused without loss of activity in a test of ten cycles. The Cp₂Ti(OSO₂C₈F₁₇)₂ catalyst affords a simple, efficient and general method for the acylation of alcohols, phenols, thiols, and amines.     

Synthesis of trisubstituted alkenes by reductive dehydroxylation of Baylis-Hillman adducts using polymethylhydrosiloxane (PMHS) and catalytic B(C6F5)3

B(C₆F₅)₃ as a catalyst and polymethylhydrosiloxane as a hydride source have been employed for the reductive dehydroxylation of Baylis-Hillman adducts wherein the hydride adds in an S_N2′ manner onto the unactivated allyl alcohol moiety with concomitant elimination of the hydroxy group along with double bond migration. The products formed were found to be E in the case of ester adducts and Z in the case of nitrile adducts.     

Synthesis and characterization of fluorous (S)- and (R)-1-phenylethylamines that effect heat facilitated resolution of (±)-2-(8-carboxy-1-naphthylsulfinyl)benzoic acid via diastereomeric salt formation and study of their circular dichroism

Perfluoroalkyl- or nonafluoro-tert-butoxy-alkyl-substituted enantiopure amines having the structure PhCHCH₃(NR¹R²) [R¹ = H, CH₃; R² = (CH₂)₃C₈F₁₇, (CH₂)₂OC(CF₃)₃; R¹ = R² = (CH₂)₃C₈F₁₇, (CH₂)₂OC(CF₃)₃] are obtained in high yields, when (S)-(−)-1-phenylethylamine is reacted with readily accessible alkylating reagents or fluorous 2° amines (R¹ = H; R² = (CH₂)₃C₈F₁₇, (CH₂)₂OC(CF₃)₃) are methylated in a Leuckart-Wallach reaction. The solubility patterns of these novel chiral amines and their hydrochlorides are qualitatively described for a broad spectrum of solvents and the fluorous partition coefficients of the free bases are determined by GC. A novel method for the resolution of enantiomers is disclosed here, which involves the use a half-equivalent of the selected resolving agent in solvent water that displays low solubility for the crystalline diastereomeric salt(s) formed even at temperatures near to its boiling point. Compound (S)-(−)-PhCHCH₃[NH(CH₂)₃C₈F₁₇] is found to satisfy all the latter conditions and successfully used for the heat facilitated resolution of the title racemic acid. The circular dichroism (CD) spectra of six novel fluorous (S)-(−)-1-phenylethylamine derivatives are measured in ethanol, trifluoroethanol and hexafluoropropan-2-ol and discussed in detail.     

Rh(PPh3)3Cl/Tetrakis(Dialkylamino)Phosphonium Salts as Thermoregulated and Recyclable Catalytic System for Hydrosilylation Reaction

Abstract

Eleven tetrakis(dialkylamino)phosphonium salts have been prepared and were used as “soft” catalyst supports for the hydrosilylation reaction of styrene with triethoxysilane catalyzed by Rh(PPh₃)₃Cl. Among the Rh(PPh₃)₃Cl/tetrakis(dialkylamino)phosphonium salts tested, the best catalytic activity and selectivity in favor of the β-adduct were obtained when {[(C₄H₉)₂N]₃[(C₈H₁₇)₂N]P}PF₆ was used as the support, and Rh(PPh₃)₃Cl/ {[(C₄H₉)₂N]₃[(C₈H₁₇)₂N]P}PF₆ catalyst system can be reused more than 10 times without noticeable loss of catalytic activity and selectivity.

GRAPHICAL ABSTRACT      

Air-stable μ2-hydroxyl bridged cationic binuclear complexes of zirconocene perfluorooctanesulfonates: their structures,characterization and application

Three air-stable zirconocene perfluoro-octanesulfonates were successfully synthesized by treatment of C₈F₁₇SO₃Ag with (RCp)₂ZrCl₂ [R?=?H, n-Bu, t-Bu]. According to X-ray analysis, they have μ²-hydroxyl bridged cationic binuclear structures: (i) [CpZr(OH₂)₃]₂(μ²-OH)₂(OSO₂C₈F₁₇)₄·2THF·4H₂O (1a·2THF·4H₂O), (ii) [n-BuCpZr(OH₂)₃]₂(μ²-OH)₂(OSO₂C₈F₁₇)₄·6H₂O (2a·6H₂O), and (iii) [t-BuCpZr(OH₂)₃]₂(μ²-OH)₂(OSO₂C₈F₁₇)₄·2C₃H₆O·8H₂O (3a·2C₃H₆O·8H₂O). The ligands of water and organic molecules in the complexes originated from the moist air and solvent during their recrystallization. These complexes were characterized with different techniques, and found to show water tolerance, air/thermal stability as well as strong Lewis acidity. Moreover, the complexes showed highly catalytic activity in various reactions of CC bond formation. With good recyclability, they should find wide applications in organic chemistry.     

Tin(IV) bis(perfluoroalkanesulfonyl)amide complex as a highly selective Lewis acid catalyst for Baeyer-Villiger oxidation using hydrogen peroxide in a fluorous recyclable phase

Sn[N(SO₂C₈F₁₇)₂]₄ catalyst was shown to give an excellent yield and selectivity in a fluorous biphasic catalytic system for Baeyer-Villiger oxidation of cyclic ketones by 35% aqueous hydrogen peroxide, a green, safe and cheap oxidant. Furthermore, the catalyst was completely recovered and reused in the fluorous immobilized phase without loss of activity.     

Application of axially dissymmetric ligand recoverable with fluorous solvent as a chiral auxiliary

(Ra)-(R)₂-2,2′-Bis(1-hydroxy-1H-perfluorooctyl)biphenyl ((Ra)-(R)₂-1c), which is an axially dissymmetric ligand with two chiral centers, works as a good chiral auxiliary for asymmetric aldol reaction. Thus, the reaction of monopropanoyl ester of 1c (2) with benzaldehyde in the presence of triethylamine and titanium(IV) chloride gave (2R),(3S)- and (2R),(3R)-3-hydroxy-2-methyl-3-phenylpropanoic acid esters (3a) in an approximate ratio of 4:1 in a total high yield. This result shows that stereoselectivity at 2-position is quite high, while that at 3-position is moderate. Both isomers were easily separated by column chromatography. Methanolysis of the separated isomers gave nearly quantitative recovery of 1c by extraction with a fluorous solvent without any loss of ee, while methyl (2R),(3S)- or (2R),(3R)-3-hydroxy-2-methyl-3-phenylpropanoates were obtained by CH₂Cl₂ extraction quantitatively in >99% ee. Aldol reaction of 2 with various aldehydes gave similar results.     

Tris(pentafluorophenyl)borane [B(C6F5)3]-catalyzed Friedel-Crafts reactions of activated arenes and heteroarenes with α-amidosulfones: the synthesis of unsymmetrical triarylmethanes

Tris(pentafluorophenyl)borane [B(C₆F₅)₃] has found to be an efficient catalyst for Friedel-Crafts reactions between activated arenes or heteroarenes and α-amidosulfones. The products undergo further Friedel-Crafts reactions with activated heteroarenes leading to the synthesis of unsymmetrical triarylmethanes. The present synthetic method displayed significant advantages such as low catalyst loading, mild reaction conditions, highly regioselective, high yield, and broad applicability to various substrates.     

Simple and Efficient One-Step Synthesis of a Highly Enantioselective Catalyst 3,3′-Di(pyrrolidinylmethyl)-H8BINOL

A concise one-step synthetic method was developed to prepare (S)-3,3′-di(pyrrolidinylmethyl)-H₈BINOL via Mannich-type reaction. Under the optimal reaction conditions, the yield reached 83% (by recrystallization) and 93% (by column chromatography). This new procedure has reduced the molar ratio of pyrrolidine/paraformaldehyde/(S)-H₈BINOL from 58:58:1 to 3:3:1, which simplified the previously reported two-step reaction to a one-step reaction with no need for laborious operations such as cooling and solvent degassing, and avoided discharging a large amount of dioxane-containing waste water.     

Fluorinated phosphorus compounds: Part 8. The reactions of bis(fluoroalkyl) phosphorochloridates with sulfur nucleophiles

The reactivity of bis(fluoroalkyl) phosphorochloridates to nucleophiles is summarised. Previous data and the results described here indicate that reactivities decrease in the order: amines>alcohols>thiols. The synthesis of CF₃CH₂OP(O)(SEt)₂ in 30% yield was accomplished by treating CF₃CH₂OP(O)Cl₂ with two molar equivalents of EtSH and Et₃N in ether. The chloridates (CF₃CH₂O)₂P(O)Cl and (C₂F₅CH₂O)₂P(O)Cl did not react with MeSH in ether at −78 °C or when heated with Pb(SMe)₂ in benzene. Ethanethiol and propanethiol reacted with fluorinated chloridates in the presence of triethylamine to give thiolates (R_FO)₂P(O)SR in 13-41% yield where R_F was CF₃CH₂, C₂F₅CH₂, C₃F₇CH₂ or (CF₃)₂CH and R was Et or n-Pr. Similarly, reaction of phosphorobromidates (R_FCH₂O)₂P(O)Br, made by brominating the corresponding bis(fluoroalkyl) H-phosphonates, with benzenethiol gave derivatives (R_FCH₂O)₂P(O)SPh in 43 and 46% yield where R_F was CF₃ and C₂F₅, respectively. Treatment of the chloridothiolate Cl(EtO)P(O)SMe, prepared in two steps from triethyl phosphite, with fluoroalcohols and triethylamine in ether gave species R_FO(EtO)P(O)SMe in 62-74% yield where R_F was CF₃CH₂, C₂F₅CH₂, C₃F₇CH₂ or (CF₃)₂CH. The reactions of bis(trifluoroethyl) phosphorochloridate with 2-mercaptoethanol, 3-mercaptopropanol and ethane-1,2-dithiol gave several unexpected products whose structures were tentatively assigned.     

Hf(OTf)4-Catalyzed Three-Component Synthesis of N-Carbamate-Protected β-Amino Ketones

Hafnium(IV) triflate (Hf(OTf)₄) has been identified as a potent catalyst for the direct three-component synthesis of β-carbamate ketones. This new method, featuring a low catalyst loading, fast reaction rate, and solvent-free conditions, provided facile access to a diversity of carbamate-protected Mannich bases. A mechanistic investigation indicated that the three-component reaction proceeds via sequential aldol condensation and aza-Michael addition, but not the Mannich-type pathway.     

Brønsted acid-mediated ring-opening reactions of methylenecyclopropanes: a dramatic counter ion effect

We report herein two different ring-opening patterns of methylenecyclopropanes (MCPs) in the presence of two Brønsted acids heptadecafluorooctane-1-sulfonic acid (C₈F₁₇SO₃H) and toluene p-sulfonic acid (TsOH) under mild conditions: (a) the ring-opening of MCPs by H₂O and subsequent etherification give the corresponding homoallylic ethers in the presence of heptadecafluorooctane-1-sulfonic acid; (b) the direct ring-opening of MCPs by the Brønsted acid gives the corresponding homoallylic alcohol derivatives in the presence of toluene p-sulfonic acid.