Transition metal catalyzed synthesis of 5-azaindoles

In an effort to develop synthetic procedures for the preparation of 2-substituted 5-azaindoles, the synthesis and cyclization reactions of acetylenic aminopyridines was explored. A novel method for the synthesis of 2-substituted 5-azaindoles via a transition metal catalyzed reaction is described.     

Copper oxide nanoparticles catalyzed synthesis of aryl sulfides via cascade reaction of aryl halides with thiourea

Recyclable copper oxide nanoparticles catalyzed simple and highly efficient protocol for the synthesis of symmetrical aryl sulfides was developed by the cross-coupling of aromatic halides with inexpensive and commercially available thiourea which was used as an effective sulfur surrogate. The present cross-coupling protocol of thiourea, via cascade reaction with various substituted aryl halides, producing desired aryl sulfides, has an added advantage of avoiding foul-smelling thiols.     

A facile one-pot synthesis of alkyl aryl sulfides from aryl bromides

A convenient one-pot synthetic method for the formation of alkyl aryl sulfides from various alkyl halides and lithium aryl thiolates that are prepared in situ by direct halogen-lithium exchange is reported. In particular, the method overcomes many of the problems encountered in previous reports; it is very quick, catalyst-free, and does not involve use of unstable aryl thiols.     

Transition metal catalyzed cationic polymerizations

Certain complexes of platinum, rhodium, iridium and cobalt are capable of initiating cationic vinyl and ring-opening polymerizations in the presence of a Si-H containing cocatalyst. An investigation has shown that two distinctly different mechanisms are involved, however, in both cases cationic polymerization can be explained by the formal attack of an electrophilic silicon species on the monomers. Since the transition metal complexes listed above also are catalysts for hydrosilation reactions, it is possible to carry out simultaneous cationic polymerizations and hydrosilation reactions to prepare novel and interesting polymers and oligomers.     

Nickel-catalyzed synthesis of aryl trifluoromethyl sulfides at room temperature

Inexpensive nickel-bipyridine complexes were found to be active for the trifluoromethylthiolation of aryl iodides and aryl bromides at room temperature using the convenient [NMe(4)][SCF(3)] reagent.     

Highly chemoselective synthesis of aryl allylic sulfoxides through calcium hypobromite oxidation of aryl allylic sulfides

A highly chemoselective oxidation of widely substituted aryl allylic sulfides, prepared by allylation of arylthioethers with KF-Celite, to the corresponding aryl allylic sulfoxide was achieved by employing calcium hypobromite. Neither over-oxidation to sulfones nor halogenation of the aromatic rings was observed. The protocol may be successfully applied for the oxidation of substituted allylic systems (i.e., 2-haloallyl) that per se could interact with the oxidizing agent.     

One-pot synthesis of symmetrical and unsymmetrical aryl sulfides by Pd-catalyzed couplings of aryl halides and thioacetates

Aryl sulfides were obtained from the coupling reaction of S-aryl (or S-alkyl) thioacetates and aryl bromides in the presence of palladium catalyst. This reaction method enables the one-pot synthesis of symmetrical and unsymmetrical diaryl sulfides by employing potassium thioacetate with aryl iodides and aryl bromides.     

铜催化硫代硫酸钠与卤代芳烃偶联的无硫醇路径合成二芳基硫化物

报道了一个在聚乙二醇中由卤代芳烃合成不同二芳基硫化物的高效方法.在Cu催化剂作用下,无味、易得、稳定的Na2S2O3· 5H2O盐是有效的硫源.     

Transition metal catalyzed alternating copolymerizations of olefins and co

Well defined Pd(II) catalysts of the type (N′N)Pd(CH₃)(Solv.)⁺ B(Ar_f)₄- (Ar_f = −3, 5-(CF₃)₂C₆H₃) have been prepared for living alternating copolymerizations of olefins with CO. This talk will focus on the mechanistic details of chain growth as elucidated by ¹H and ¹³C NMR spectroscopy, model studies of key migratory insertion steps and synthesis and properties of various copolymers and block copolymers based on styrenes, CH₂=CHC₆H₄X [X = p-C(CH₃)₃, p-OC(O)CH₃, p-OC(O)C-t-Bu), p-NHC(O)(C-t-Bu)]. Use of the catalysts based on the C₂ symmetric, homochiral ligand 2, 2'-bis[2-[4(S)-(Alkyl)-1, 3-oxazolinyl]]propane [Alkyl = CH₃, CH(CH₃)₂] produces a copolymer, 1, with a highly isotactic microstructure and high optical activity in contrast to achiral ligands such as 1,10-phenanthroline which produce copolymers with predominantly syndiotactic microstructure.     

Transition metal free one pot synthesis of aryl carboxylic acids via dehomologative oxidation of styrenes

Iodine/NaOH-catalyzed one-pot dehomologative oxidation of styrenes to aryl carboxylic acids has been reported. A wide range of carboxylic acids are obtained using iodine (I₂) as a catalyst, tert-butyl hydroperoxide (TBHP) as an oxidant and sodium hydroxide (NaOH) as a base. This reliable conversion involves dehomologation of styrene to aromatic aldehyde which on subsequent oxidation affords aryl carboxylic acid. This protocol was used for gram-scale synthesis as it is free from chromatographic purification. This is the first report for the oxidative transformation of styrenes into aryl carboxylic acids under transition metal-free conditions.     

Role of electron transfer processes in the oxidation of aryl sulfides catalyzed by nonheme iron complexes

ABSTRACT

The oxidation of a series of aryl 1-methyl-1-phenylethyl sulfides with H₂O₂ catalyzed by the two tetradentate nonheme-iron complexes [(PDP)Fe^II(SbF₆)₂] and [(BPMCN)Fe^II(OTf)₂] occurs by an electron transfer-oxygen transfer (ET/OT) mechanism as supported by the observation of products deriving from fragmentation of the corresponding radical cations in association with S-oxidation products (sulfoxides).     

New insights into the titanium-mediated enantioselective oxidation of fluorinated aryl benzyl sulfides and aryl phenacyl sulfides

A fruitful switch from tert-butyl to cumene hydroperoxide was able to overcome a difficulty arose in the enantioselective oxidation of fluorinated aryl benzyl sulfide with hydroperoxides in the presence of a titanium/(S, S)-hydrobenzoin catalyst. New experiments show the complementarity of the old and the new protocols and indicate unequivocally the right choice leading to the corresponding highly enantioenriched sulfoxides. Moreover, in a totally unexpected way, the new protocol was able to overcome another difficulty arose in another field of research, that is the enantioselective oxidation of a fluorinated aryl phenacyl sulfide. Also in this case, the complementarity of behavior is acting. Finally, this investigation gives new support to the attribution of configuration of sulfoxides with ECD techniques, but only if the protocol outlined in our past research was followed thoroughly.     

Direct synthesis of diaryl sulfides by copper-catalyzed coupling of aryl halides with aminothiourea

An efficient and simple protocol of copper-catalyzed C-S bond formation between aryl halides and inexpensive and commercially available aminothiourea is reported.A variety of symmetrical diaryl sulfides can be synthesized in good to excellent yields up to 94%with the advantage of avoiding foul-smelling thiols.     

Amberlyst-15 catalyzed synthesis of alkyl/aryl/heterocyclic phosphonates

A novel and efficient procedure for the synthesis of alkyl phosphonates through one pot condensation of alkyl halide and trialkyl /aryl phosphite in the presence of Amberlyst-15 as catalyst under solvent free conditions was applied.It demonstrated several advantages such as good yields of products,simple operation,convenient separation and inexpensive catalyst.     

Facile synthesis of aryl(het)cyclopropane catalyzed by palladacycle

Sphos (2-dicyclohexylphosphino-2′,6′-dimethoxy-1,1′-biphenyl) adduct of cyclopalladated ferrocenylimine (IIe) exhibited highly catalytic activity for the Suzuki cross-coupling reaction of cyclopropylboronic acid with aryl(het) halides with 1 mol % catalyst loading. This process was applied to both of aryl and heteroaryl halides (Br and Cl), and made the various arylcyclopropane and heteroarylcyclopropane to be easily synthesized. A variety of substituents on the aryl halides, such as alkyl, acetyl, benzoyl, ether, formyl, carboxylate, methoxy, nitro and cyano were tolerated.     

Transition metal catalyzed cross-coupling of aryl Grignard reagents with aryl fluorides via Pd- or Ni-activation of the C-F bond: an efficient synthesis of unsymmetrical biaryls - application of microwave technology in ligand and catalyst screening

Biaryl compounds are prevalent in both nature and in active pharmaceutical ingredients. The palladium and nickel catalyzed cross-coupling of aryl Grignard reagents with aryl fluorides reported herein affords moderate to excellent yields of the corresponding unsymmetrical biaryls. In addition, the first example of a biaryl cross-coupling utilizing unactivated aryl fluorides under phosphine free palladium conditions is reported. Microwave technology allowed rapid optimization of catalyst systems, which identified several ligands for this cross-coupling reaction.     

A simple one-pot synthesis of hydroxylated and carboxylated aryl alkyl sulfides from various bromobenzenes

A simple one-pot synthesis of aryl alkyl sulfides from various bromobenzenes containing a hydroxy, hydroxymethyl, hydroxyethyl, and carboxylic acid group at -o, -m, and -p positions is reported here. The reaction proceeds through, in sequence, in situ protection of the hydroxy or carboxylic acid group by reaction with a Grignard reagent, lithium-halogen exchange, the formation of lithium thiolates, and the nucleophilic attack of lithium thiolates on various electrophiles without isolation of the thiolates, in one vessel. This procedure required a very short reaction time (1-1.5 h) and gave the corresponding sulfides in 75-97% yields.