Nickel(0)-catalyzed diastereoselective three-component coupling of 1,3-dienes, aldehydes, and organometallic reagents: influence of organometallic reagents on diastereoselectivity

A nickel-catalyzed diastereoselective alkylative three-component coupling of 1,3-diene and aldehyde with organoboron or organosilicon reagents has been realized. The diastereoselectivity was dramatically changed depending on the class of organometallic reagents. The reaction using ArB(OH)₂ in the presence of PPh₃ afforded 1,3-syn-substituted 4-penten-1-ol derivative as a single diastereomer. On the other hand, the coupling reaction with tetraorganosilicon reagent using NHC as a ligand under similar conditions exclusively produced the corresponding 1,3-anti isomer.     

Stereoselective Ag‐Catalyzed 1,3‐Dipolar Cycloaddition of Activated Trifluoromethyl‐Substituted Azomethine Ylides

A silver‐catalyzed 1,3‐dipolar cycloaddition of fluorinated azomethine ylides and activated olefins is reported. The reaction offers a straightforward and atom‐economical procedure for the preparation of fluorinated pyrrolidines. Broad scope and high levels of diastereoselectivity have been achieved simply by using AgOAc/PPh₃ as the catalyst system. The high efficiency of the cycloaddition relies on the presence of a metal‐coordinating group on the imine moiety, such as an ester or heteroaryl group. The asymmetric version of the cycloaddition has been developed by using Taniaphos as a chiral ligand.     

Regiospecific synthesis of symmetrical (1E,3E) 2,3-difluoro-1,4-diphenyl-buta-1,3-dienes via palladium-catalyzed cross-coupling of (Z) 2-bromo-2-fluoroethenylbenzenes in presence of bis(pinacolato)diboron

The cross-coupling reaction of (Z) 1-bromo-1-fluoroalkenes catalyzed by PdCl₂(PPh₃)₂-2PPh₃ (3%) and CsF in Tetrahydrofuran (THF) in presence of bis(pinacolato)diboron led to (1E,3E) 2,3-difluoro-1,4-disubstituted-buta-1,3-dienes in high yields.     

A simple route to metalla-2-indane-1,3-diones

A simple and high yielding synthesis of metalla-2-indane-1,3-diones (phthaloyl metal complexes) by the insertion of low-valent transition metal complexes (ClRh(PPh₃)₃, ClCo(PPh₃)₃, Fe(CO)₅) into benzocyclobutenedione is reported. The structure of the rhodium complex was established by an X-ray analysis.     

A novel one-pot synthesis of 2-arylpyrazoloquinolinone derivatives

Two regioisomers of 2-arylpyrazolo[3,4-c]quinolin-4(5H)-ones and 2-arylpyrazolo[4,3-c]quinolin-4(5H)-ones were synthesized by utilizing 3-arylsydnones, ethyl 3-bromopropynoate, and 2-aminophenylboronic acid pinacol ester in presence of catalytic agent Pd(PPh₃)₄. This efficient one-pot synthesis methodology involved 1,3-dipolar cycloaddition, Suzuki coupling reaction, and intramolecular cyclization three sequence steps.     

Modification chimique des polyalcadiènes par les composés du type CX3Z—I Addition catalysée des composés CCl3Z sur les polybutadiènes-1,2

The influence of catalysis on chemical modification of 1,2-polybutadienes (M_n < 10,000) by CX₃Z reagents (X = halogen; Z = functional group or halogen), in order to obtain polymers soluble in common solvents, has been studied. The work has been carried out with carbon tetrachloride, trichloromethylphosphonyldichloride (CCl₃POCl₂) and ethyl trichloroacetate (CCl₃CO₂Et) in the presence of solvents such as C₆H₆, CH₂Cl₂. Among the compounds tested as catalysts for the addition of CX₃Z to 1,2-polybutadiene (transition metal salts and complexes; radical initiators) only the systems formed with metal salts such as CuCl₂, FeCl₃, RuCl₃ 3H₂O, Fe₂(CO)₉ and Cl₂Ru(PPh₃)₃ were found to show high catalytic activity. The most active is Cl₂Ru(PPh₃)₃: used without or with cocatalysts (Et₃NHCl/benzôin, alcohols), it leads always, to the best yields whatever the nature of CX₃Z. The activity of the other catalysts is generally dependent on CX₃Z structure. Some secondary reactions (cross-linking, cyclization, transesterification) have been found.     

Synthesis of N-acetyl-3,3a,4,8b- and -1,3a,4,8b-tetrahydrocyclopenta[b]indoles from N- and 2-(cyclopent-2-en-1-yl)anilines

Reactions of 2-bromo-N-(cyclopent-2-en-1-yl)-4-methylaniline and N-(cyclopent-2-en-1-yl)-2-iodo-4,6-dimethylaniline with acetyl bromide in the presence of potassium carbonate gave mixtures of syn and anti atropisomers of the corresponding N-acetyl derivatives at ratios of 1: 1 and 3: 2 respectively. Heating of these mixtures in toluene in the presence of Pd(OAc)₂, PPh₃, Et₃N, and K₂CO₃ (KOAc) afforded mixtures of isomeric N-acetyl-7-methyl-3,3a,4,8b- and -1,3a,4,8b-tetrahydrocyclopenta[b]indoles at a ratio of 3: 1 or N-acetyl-5,7-dimethyl-3,3a,4,8b- and -1,3a,4,8b-tetrahydrocyclopenta[b]indoles at a ratio of 2: 3. N-Acetyl-3,3a,4,8b-tetrahydrocyclopenta[b]indole was found to undergo thermal isomerization into N-acetyl-1,3a,4,8btetrahydrocyclopenta[b]indole.     

Facile and efficient synthesis of fluorinated fullerene-fused 1,3-dioxolanes: reaction of C60 with fluorinated aromatic aldehyde mediated by lithium perchlorate

A series of fluorinated fullerene-fused 1,3-dioxolanes have been facilely and efficiently synthesized in the presence of easily available LiClO₄·3H₂O. The influences of the number of fluoro-substituents and their positions linked to the phenyl ring on the isolated yield of fullerene-fused 1,3-dioxolanes have been studied in detail. Based on reaction facts, a possible reaction mechanism for the formation of fluorinated fullerene-fused 1,3-dioxolanes has been proposed. Furthermore, detailed ultraviolet absorption spectra, fluorescence emission spectra, and cyclic voltammogram further explain the optical properties and electronic transmission capabilities of the products.     

Synthesis of oxoindolin-3-ylidene-1,3-dithioles

An efficient and one-pot synthesis of 2-(2-oxoindolin-3-ylidene)-1,3-dithiole-4,5-dicarboxylates by a three-component condensation reaction of isatins, carbon disulfide and dialkyl acetylendicarboxylates in the presence of Bu₃P is reported. Reaction of carbon disulfide and dialkyl acetylene dicarboxylates with acenaphthylene-1,2-dione, ninhydrine and pyrimidine-tetraone resulted in the formation of 2-(2-oxoacenaphthylen-1(2H)-ylidene)-1,3-dithiole-4,5-dicarboxylates, 2-(1,3-dioxo-1H-inden-2(3H)-ylidene)-1,3-dithiole-4,5-dicarboxylates and 2-(2,4,6-trioxotetrahydropyrimidin-5(6H)-ylidene)-1,3-dithiole-4,5-dicarboxylates, respectively, in the same conditions.     

The kinetics and mechanism of diene exchange in (η4-enone) Fe(CO)2L complexes (L = phosphine,phosphite)

Kinetic data for the exchange of 1,3-cyclohexadiene with (η⁴-benzylideneacetone)Fe(CO)₂L complexes (L = CO, PPh_3-xMe_x (x = 0-2) or P(OPh)₃) to give (η⁴-1,3-cyclohexadiene)Fe(CO)₂L derivatives indicate a mechanism involving stepwise competing D and I_d opening of the ketonic M-CO π-bond. Rates increase in the order CO ? PPh₃ ≈ P(OPh)₃ > PPh₂Me ? PPhMe₂, and both steric and electronic factors appear to be important. (η⁴-1,3-cyclohexadiene)Fe(CO)₂L complexes of potential use in enantioselective synthesis (L=(+)-Ph₂P(menthyl) or (+)-Ph₂PCH₂CH(Me)Et) may be prepared via their (η⁴-benzylideneacetone)Fe(CO)₂L complexes.     

Palladium-catalyzed [3+2+1] cyclocarbonylative coupling of 1,3-cyclohexanediones, alkynes, and carbon monoxide: an atom-economic route to chromene-2,5-dione derivatives

3,4,7,8-Tetrahydro-2H-chromene-2,5(6H)-dione derivatives were efficiently synthesized with excellent selectivity via a [3+2+1] cyclocarbonylative coupling of 1,3-cyclohexanediones, terminal alkynes, and CO catalyzed by Pd(PPh₃)₄.     

The unexpected cyclization routes of N,N′-bis(oxotrifluoroalkenyl)-1,3-phenylenediamines in polyphosphoric acid medium

The unexpected results of the cyclization reactions of N,N′-bis(oxotrifluoroalkenyl)-1,3-phenylenediamines [1,3-C₆H₄-(NHCRCHC(O)CF₃)₂], where R = H, Me, and Ph, in a strongly acidic medium (PPA), allowing the synthesis of new trifluoromethylated heterocycles containing the 1,7-phenanthroline nucleus in 32-40% yields and 7-aminoquinolines (38-40% yields), is reported. The bis-enaminoketone intermediates were easily isolated from the reactions of 4-alkoxy-4-alkyl(aryl)-1,1,1-trifluoroalk-3-en-2-ones with 1,3-phenylenediamine in ethanol under mild conditions (68-86% yields).     

Orthogonal synthesis of pyrroles and 1,2,3-triazoles from vinyl azides and 1,3-dicarbonyl compounds

Tri- and tetrasubstituted N-H pyrroles were prepared by the simple treatment of vinyl azides with 1,3-dicarbonyl compounds in toluene at 100 °C via 2H-azirine intermediates generated in situ. When the reactions of vinyl azides and 1,3-dicarbonyl compounds were performed in DMF in the presence of a catalytic amount of K₂CO₃, 1-vinyl-1,2,3-triazoles were obtained via 1,3-dipolar cycloaddition. These methodologies exploited orthogonal modes of chemical reactivity of vinyl azides, which could be achieved by slight modification of the reaction conditions.     

Palladium-Catalyzed Synthesis of 3-Alkylphthalides via Carbonylative Cyclization of o-Bromobenzaldehyde with 1,3-Dicarbonyl Compounds

o-Bromobenzaldehyde reacts with 1,3-dicarbonyl compounds under carbon monoxide in the presence of a catalytic amount of PdCl₂(PPh₃)₂ to give the corresponding 3-alkylphthalides in moderate to good yields.     

A New Efficient and Stereoselective Synthesis of 1,3E,5Z-Undecatriene

1,3E,5Z-Undecatriene is synthesized by coupling of Z-heptenyl copper reagent, obtained through carbocupration of acetylene, with 1-chloro-1E,3-butadiene, in the presence of 5% NiCl₂(PPh₃)₂     

Nickel-catalyzed coupling of bromides of 1,6-methano[10]annulene and azulene. A facile synthesis of biannulene and bi-, ter-, quater-, and polyazulenes

The active nickel complex generated in situ by reduction of NiBr₂(PPh₃)₂ with zinc in the presence of Et₄NI is a useful reagent for the dehalogenative coupling of 2-bromo-1,6- methano[10]annulene and 1-bromo- and 1,3-dibromoazulenes.     

Nickel-catalyzed [4+3] cycloaddition of ethyl cyclopropylideneacetate and 1,3-dienes

The [4+3] cycloaddition of ethyl cyclopropylideneacetate (1) with 1,3-dienes proceeded in the presence of Ni(cod)₂-TOPP (tri-o-biphenylyl phosphite). The reaction provided a new method for the synthesis of cycloheptene derivatives. The mechanism of the reaction was proposed.     

Pd(O) promoted transformation of N-tosyl-2-(1,3-butadienyl)-aziridine into N-tosyl-2-vinyl-3-pyrroline

1,3-Butadienylaziridines activated by N-tosyl group smoothly rearrange to vinylpyrrolidine derivatives in the presence of a catalytic amount of Pd(PPh₃)₄. Transformation of dienylazetidines into vinylpiperidine derivatives is also described.     

gem-Difluorosubstituted NH-azomethine ylides in the synthesis of 4-fluorooxazolines via the three-component reaction of imines, trifluoroacetophenones and CF2Br2

A simple one-step synthesis of a new class of fluorinated heterocycles, 4-fluoro-3-oxazolines, from diarylmethanimines, trifluoroacetophenones and CF₂Br₂ is described. The reaction proceeds via the sequential formation of difluorocarbene and a gem-difluorosubstituted NH-azomethine ylide, followed by 1,3-dipolar cycloaddition with a ketone.     

[Bis(tetrahydrofuran–O)–bis(1,3–dialkyl–2–diphenylphosphanyl–1,3–diazaallyl)calcium] – Synthesis and Crystal Structures of Calcium Bis[phospha(III)guanidinates] and Investigations of Catalytic Activity

The reaction of [(thf)₄Ca(PPh₂)₂] ( 1 ) with diisopropyl– and dicyclohexylcarbodiimides yields the phospha(III)guanidinates [(thf)₂Ca{RNC(PPh₂)NR}₂] with R = isopropyl ( 2 ) and cyclohexyl ( 3 ). The metathesis reaction of K{RNC(PPh₂)NR} with anhydrous CaI₂ also allows the synthesis of these phospha(III)guanidinate complexes 2 and 3 . For 2 a cis arrangement is observed whereas 3 crystallizes as trans isomer. The phospha(III)guanidinates act as bidentate chelate bases with an average Ca–N distance of 242.5 pm. The C–P bond length between the PPh₂ fragment and the 1,3–diazaallyl unit is with values above 190 pm very large. The complexes 2 and 3 show a moderate catalytic activity in hydrophosphanylation reactions of dialkylcarbodiimides with diphenylphosphane.