Asymmetric cyclizations via a sequential Michael addition/Conia-ene reaction by combining multifunctional quaternary phosphonium salt and silver catalysis

A one-pot asymmetric Michael addition/Conia-ene reaction sequence, catalyzed by combination of a dipeptide-derived multifunctional quaternary phosphonium salt and Ag₂CO₃ has been developed, which provides a series of synthetically important chiral methylenecyclopentane derivatives in moderate to excellent yields (up to 97%) and enantioselectivities (up to 93%).     

Novel Mild Synthesis of N-Carboxylotriphenylphosphin-Imines & Id N-Amidotriphenylphosphinimines VIA Ligand Exchange Processes in Dichlorotriphenylphosphine

Abstract

In connection with our recent investigations on the ligand exchange processes in five-coordinated phosphoranes and phosphonium salts a new, one-pot synthesis of various N-carboxylotriphenylphosphinimines 1 and N-amidotriphenylphosphinimines 2 has been devised. The key intermediate, phosphonium salt 4, was obtained in quantitative yield by the reaction of Ph₃PCl₂ with cyanate salts Pb(OCN)₂ and NaOCN. When alcohols or amines were present, salt 4 was converted into 1 and 2:     

Action des derives du phosphore trivalent sur les composes a halogene positif—VII : Cycloaddition avec les sels d'(α-cetoceteniminyl) phosphonium

The reaction of phosphines (Ph₃P, (pMeC₆H₄)₃P) with α-cyano α-haloimides gives, by attack on halogen, an ion-pair, which rearranges into a (α-ketoketeniminyl)phosphonium salt. When P(NMe₂)₃ is used, the nucleophilic attack of the anion O-atom at the halophosphonium cation-P atom is also observed. The α-ketoketeniminyl phosphonium salts give α-haloiminophosphoranes or oxazines by cycloaddition with the anion of the ion pair.     

Boron Perturbed Click Reactions Prompt Aromatic C?H Activations

The reaction of boron alkynes and boron azides leads to rare N₃BC heterocycles resulting from aromatic C H activation of benzene and toluene. While subsequent treatment with PMe₃ gave the P B adduct with the exocyclic boron, reaction with PtBu₃ effected deprotonation of the heterocycle to give the corresponding phosphonium salt.     

Boron Perturbed Click Reactions Prompt Aromatic CH Activations

The reaction of boron alkynes and boron azides leads to rare N₃BC heterocycles resulting from aromatic C? H activation of benzene and toluene. While subsequent treatment with PMe₃ gave the P? B adduct with the exocyclic boron, reaction with PtBu₃ effected deprotonation of the heterocycle to give the corresponding phosphonium salt.     

Preparation of chlorofluoromethylene olefins via phosphine dechlorination of dichlorofluoromethyltris?dimethylamino?phosphonium chloride

The reaction of dichlorofluoromethyltris?dimethylamino?phosphonium chloride with tertiary phosphines provides a convenient preparation of the chlorofluoromethylenetris?dimethylamino?phosphonium ylide. This ylide provides reasonable yields of chlorofluoroolefins from aldehydes, activated ketones, non-activated ketones, and activated esters. The mechanism of phosphonium salt formation was shown to involve positive chlorine abstraction from CFCl₃ by (Me₂N)₃P followed by recombination of the intermediate ion pair. Dechlorination of the resulting dichlorofluoromethyltris?dimethylamino?phosphonium chloride by triphenylphosphine gave an olefinating solution of reasonable stability. In contrast, the solution obtained by dechlorination of the phosphonium salt by tris?dimethylamino?-phosphine showed no stability.     

PCy3‐Catalyzed Ring Expansion of Aziridinofullerenes with CO2 and Aryl Isocyanates: Evidence for a Two Consecutive Nucleophilic Substitution Pathway on the Fullerene Cage

A PCy₃‐catalyzed ring‐expansion reaction of aziridine‐fused fullerenes (aziridinofullerenes) through the insertion of CO₂ and aryl isocyanates is disclosed. The reaction allows for CO₂ fixation by aziridinofullerenes, producing oxazolidinone‐fused fullerenes (oxazolidinofullerenes) in high yields, whereas treatment with aryl isocyanates led to a new fullerene family—imidazolidinone‐fused fullerenes (imidazolidinofullerenes)—in good to high yields. Furthermore, a mechanistically related unprecedented fullerenyl phosphonium salt was successfully isolated. Using the isolated salt, mechanistic studies were also investigated.     

A consecutive one-pot two-step approach to novel trifluoromethyl-substituted bis(indolyl)methane derivatives promoted by Sc(OTf)3 and p-TSA

A one-pot two-step reaction of 3-(trifluoroacetyl)coumarin and indole afforded trifluoromethyl-substituted bis(indolyl)methane compounds containing coumarin skeleton. The atomic economic and simply manipulative reaction involved premier treatment of reaction mixtures with Sc(OTf)₃, followed by p-TSA in one-pot process. The reaction proceeded to give the title compounds in high yields (up to 95% yield).     

Some reactions of 4H-pyrylium salts with tributylphosphine and with tertiary amines

The phosphonium salt from tributylphosphine and 2,6-di(4-methoxyphenyl)pyrylium perchlorate (3) reacted with diisopropylethylamine in acetonitrile to give 2,2′,6,6′-tetra(4-methoxyphenyl)-Δ^4.4′-bi-4H-pyran in quantitative yield. The reaction of 3 and other 4H-pyrylium salts with tertiary amines gave 4H-pyrans.     

A one-pot approach to novel α-trifluoromethylated coumarin-bearing tertiary alcohols promoted by CH3COOH/NH4OAc via consecutive ring-opening/aldol sequence

A one-pot two-step reaction of 2-(trifluoromethyl)-2-hydroxy-2H-chromene with aryl ketone afforded α-trifluoromethylated tertiary alcohols bearing coumarins. The atomic economic and simply manipulative reaction involved premier treatment of reaction mixtures with CH₃COOH and NH₄OAc in one-pot process. The reaction proceeded to give the title compounds in moderate to good yields.     

[Ph4P][(C5H6N3O3)M(CO)5] (M = Cr,Mo, W; C5H7N3O3 = 1,3‐Dimethyl‐cyanuric Acid). Organometallic Complexes of the 1,3‐Dimethylcyanurate Ligand

1,3‐Dimethylcyanuric acid (DMCH) forms on deprotonation and reaction with TlF its thallous salt Tl[DCM] ( 2 ) which is converted to the phosphonium salt [PPh₄][DCM] ( 3 ). On the reaction with M(CO)₆, the pentacarbonylmetalate salts [Ph₄P][(DMC)M(CO)₅], M = Cr ( 4a ), Mo ( 4b ) and W ( 4c ) are obtained. IR and NMR data of 4 reveal the DMC anion ( 1 ) to have coordination properties similar to those of pyridine. The crystal structures of 4a and 4c are reported.     

A concise synthesis of substituted stilbenes and styrenes from propargylic phosphonium salts by a cobalt-catalyzed Diels-Alder/Wittig olefination reaction sequence

The cobalt(I)-catalyzed Diels-Alder reaction of propargylic phosphonium salts and longer chained alkyne-functionalized phosphonium salts with 1,3-dienes led to dihydroaromatic phosphonium salt intermediates which were directly used in a one-pot Wittig-type olefination reaction with aldehydes. Subsequent oxidation led to styrene- and stilbene-type products under formation of three new carbon-carbon bonds in a single synthetical step starting from three variable starting materials. The E/Z stereoselectivities of the products revealed that the dihydroaromatic phosphonium ylides behave as semistabilized ylides giving predominantly the E-configured products. The application of unsymmetrical 1,3-dienes as well as internal phosphonium functionalized alkynes is also described.     

Insoluble polystyrene-bound quaternary onium salt catalysts for the synthesis of cyclic carbonates by the reaction of oxiranes with carbon dioxide

The addition reaction of oxiranes ( 26a—e ) with carbon dioxide (CO₂) was performed using insoluble polystyrene beads containing pendant quaternary ammonium or phosphonium salts as catalysts under atmospheric pressure. The reaction of 26a—e with CO₂ proceeded smoothly catalyzed by 1–2 mol % of the polymer-supported quaternary onium salts to give the corresponding cyclic carbonates ( 27a—e ) in high yields at 80–90°C. In this reaction system, the catalytic activity of the polymer-supported quaternary onium salts was strongly affected by the following factors: degree of ring substitution (DRS) of the onium salt residues to the polymer, degree of crosslinking (DC) of the polystyrene beads, chain length of the alkylene spacer between the polymer back-bone and the onium salt, hydrophobicity of the alkyl group on the onium salts, and kind of onium salts. That is, the polymer-supported quaternary phosphonium salts with low DRS and DC and with long alkylene spacer chain were found to have higher catalytic activity than low molecualr weight quaternary onium salts. The above polymer-supported catalysts can easily be separated at the end of a reaction by filtration and can be reused for at least seven runs. It was also found that the rate of reaction was proportional to the products of catalyst concentration and oxirane concentration. © 1993 John Wiley & Sons, Inc.     

SPIONs as a nanomagnetic catalyst for the synthesis and anti-microbial activity of 2-aminothiazoles derivatives

A series of aminothiazole derivatives have been synthesized by using ultrasmall superparamagnetic iron oxide nanoparticles (SPIONs) nanomagnetic catalysis, which were prepared by reducing the Fe(II) and Fe(III) precursors using aqueous ammonia then characterized by the XRD, FTIR, SEM, and TEM. The 2-aminothiazole derivatives were obtained by coupling 2-aminothiazole diazonium salt with active methylene compounds then cyclization with hydrazine hydrate to afford pyrazolyl derivatives. The one-pot reaction of 2-aminothiazole with an aromatic aldehydes in the presence of Fe₃O₄ NPs to give Schiff bases derivatives. An efficient protocol is developed proudest yields and reduction reaction time and easy separation. Therefore, all synthesized compounds were evaluated for anti-microbial activity.     

Efficient synthesis of β-halogeno protected l-alanines and their β-phosphonium derivatives

Ring opening of oxazolines, prepared from l-serinates, with trimethylsilyl halides (TMSX) led to β-halogeno-N-benzoyl-α-amino esters in good to excellent yields. Quaternization of triphenylphosphine by the β-bromo or -iodo amino esters gave the corresponding β-phosphonium salts in overall yields of up to 93% and with e.e. >96%. Hydrolysis of the ester function afforded the phosphonium salt bearing an N-benzoyl-α-amino acid substituent, with partial racemization. However, the reaction of the TMSX with the carboxylic salt, prepared by saponification of the starting oxazoline ester, furnished the corresponding β-halogeno-N-benzoyl-α-amino acids in 70–95% yields. Quaternization of triphenylphosphine by the bromo or iodo derivatives led to the phosphonium salts bearing a free acid function in 95% yield, without racemization. The efficiency of this synthesis was demonstrated by the preparation of these phosphonium salts in excellent overall yields, by a one-pot procedure starting from the oxazoline.     

Synthesis of 1,2-disubstituted-3-alkylidenylpyrrolidines via a one-pot three-component reaction

Olsson’s three-component reaction of cyclopropylketones, aldehydes, and primary amines was investigated for application to parallel synthesis. Using an excess of Et₂AlI at elevated temperatures, pyrrolidines 4, the initial products reported by Olsson and co-workers, could be completely converted to pyrrolium salts 5, by a reaction sequence involving a retro-aza-Michael addition followed by iminium salt formation. The pyrrolium salts 5 were then cleanly reduced in situ by NaBH(OAc)₃ to give 3-alkylidenylpyrrolidines 6. In summary, this one-pot three-component reaction provided an efficient synthetic route to 3-alkylidenylpyrrolidines.     

Diphosphapodanden, [12]‐, [15]‐ und [18]Diphosphacoronanden,Diphosphacryptand‐8 und Alkalimetall‐Komplexe

Diphosphapodands, [12]‐, [15]‐, and [18]Diphosphacoronands, Diphosphacryptand‐8, and Alkali‐Metal Complexes The cyclizing bis‐phosphonium‐salt formation of the open‐chain bis‐phosphine 17a (1,1,7,7‐tetrabenzyl〈P.O.P‐podand‐7〉) with diethylene glycol derived dibromide 13a yields the 12‐membered cyclic bis‐phosphonium salt 20 (4,4,10,10‐tetrabenzyl‐12〈O.P.O.P‐coronand‐4〉‐4,10‐diium dibromide) in yields as high as 50–60%. The 1,1,10,10‐tetrabenzyl〈P.O₂.P‐podand‐10〉 17b forms with 13a the 15‐membered cyclic bis‐phosphonium salt 21 (7,7,13,13‐tetrabenzyl‐15〈O₂.P.O.P‐coronand‐5〉‐7,13‐diium dibromide) with the same high yield. By quaternization of the bis‐phosphine 17b with triethylene glycol derived dibromide 13b , the 18‐membered 7,7,16,16‐tetrabenzyl‐18〈O₂.P.O₂.P‐coronand‐6〉‐7,16‐diium dibromide 24 is obtained in 50% yield, too. The Wittig reaction of the cyclic phosphonium salts with benzaldehyde yields the 12‐, 15‐, and 18‐membered cyclic bis‐benzylphosphine dioxides 9, 10 , and 11 as cis‐ and trans‐isomers beside trans‐stilbene. The 7,13‐dioxido‐7,13‐dibenzyl‐15〈O₂.P.O₂.P‐coronand‐5〉 10 forms a crystalline 1 : 1 Na‐complex 23 , which exists as a dimer. The structure of 23 was established by an X‐ray analysis and spectroscopic data. The 7,16‐dibenzyl‐18〈O₂.P.O₂.P‐coronand‐6〉 28 that is available by reduction of 11 with CeCl₃/LiAlH₄ reacts with triethylene glycol derived dibromide 13b under Ruggly Ziegler‐dilution conditions to give the bicyclic bis‐phosphonium salt 29 (1,10‐dibenzyl〈P[O₂]₃.P‐cryptand‐8〉‐1,10‐diium dibromide) in 18% yield. Again, by the Wittig procedure with benzaldehyde, the 7,16‐dioxido〈P[O₂]₃P‐cryptand‐8〉 12 is obtained as the first diphosphacryptand. The FD‐MS (CH₂Cl₂) of the cyclic bis‐phosphine dioxides 10 – 12 show that they exist as [2M+Na]⁺ complexes. The complex formation constants K_a of 9 – 11 with alkali‐metal cations are studied and compared with the complex formation of corresponding crown ethers.     

Tris(benzophenoneimino)phosphane and Related Compounds

A new group of bases with benzophenoneiminyl (bpi) moiety has been synthesized and characterized in this work. The title compound tris(benzophenoneimino)phosphane (P(bpi)₃) 1 was prepared with a convenient one-pot approach: benzophenone imine was deprotonated using MeMgCl and reacted with PBr₃ in diglyme. The method could be considered as a method of choice for preparing other (amino)phosphanes in case lithio-intermediates and/or protonated phosphane is out of consideration. Phosphane 1 is further used to prepare a range of related phosphonium cations and phosphazenes. Phosphonium cations were deprotonated to assess the stability of the resulting phosphonium ylides. In some cases, the bulky substances were capable of forming P−N heterocycles. Experimental (MeCN) and computational (MeCN, THF, gas-phase) basicities of benzophenone imine, phosphane 1 , phosphonium ylides, and phosphazenes, as well as some representative XRD structures, are presented and discussed.     

Developing Phospha‐Stork Chemistry Induced by a Borane Lewis Acid

Bulky vinyl phosphanes undergo carbon–carbon coupling with aryl aldehydes with the help of the Lewis acid B(C₆F₅)₃ to give isolable methylene phosphonium products. Dimesityl(vinyl)phosphane undergoes a phospha‐Stork reaction with bulky enones efficiently catalyzed by B(C₆F₅)₃ to eventually yield the corresponding substituted cyclobutane products.     

Synthesis,Structure, and Properties of Novel Enamine Containing Coumarin and Phosphonium Fragments

Condensation of 4-hydroxy-3-formylcoumarin with 4-aminobenzyl(triphenyl)phosphonium bromide has led to the formation of a phosphonium salt existing in DMSO solution as a mixture of two enamine forms, Z and E, according to NMR spectroscopy and quantum-chemical simulations data. Basing on the obtained salt, the ML₂ metal chelates of zinc(II), copper(II), and nickel(II) have been synthesized. Luminescence properties of the ligand and its complex with zinc have been studied.