Syntheses et isomerisation de complexes de la serie des derives halocarbonyle due fer: [FeX(CO)5−nLn]+, FeX2(CO)4−nLn et [FeX3(CO)3]- (L = PMe3; n = 1, 2, 3; X = Cl,Br, I)

The synthesis of a number of neutral, cationic and anionic halocarbonyl complexes of iron having the formula [FeX_m(CO)_6?m?nL_n]^2?m is described. The determination of their molecular configuration by infrared, NMR and dipole moment measurements allowed the study of several of their photochemical isomerization reactions, the mechanism of these reactions is explained in some cases by the intermediary formation of cationic complexes.     

Synthesis and characterization of the ZnxCd1−xIn2S4 pseudoternary solid solution

We have synthesized several compounds of the Zn_xCd_1−xIn₂S₄ family by solid phase reactions and chemical transport reactions using iodine. The reaction products have been characterized as to composition, structure, and lattice dynamics. Here we discuss and compare the different results obtained by the two synthesis methods.     

Stereoselective allylation of acyclic and chiral α-amino-β-Hydroxy aldehydes part 2: Application to the formal synthesis of the polyhydroxylated γ-amino acid (+)-Detoxinine

Stereoselective allylations of acyclic, chiral α-amino-β-hydroxy aldehydes mediated by BF₃·OEt₂ and its application to the formal synthesis of the polyhydroxylated γ-amino acid (+)-detoxinine are described. The reactions of syn-α-NHCbz-β-OTBS substrates mediated by BF₃·OEt₂ afforded syn-selective products. The same reaction conditions gave anti-selective products from syn-α-NCbzBn-β-OTBS substrates. A hydrogen-bonded transition state and Felkin-Anh model have been suggested to account for the stereochemical outcomes of the two reactions, respectively. One of the allylation products was used for the formal synthesis of the polyhydroxylated γ-amino acid (+)-detoxinine.     

Efficient and regioselective functionalization of imidazo[1,2-b]pyridazines via palladium-catalyzed cross-coupling reaction and SNAr

The synthesis of 3,6-disubstituted-2-phenylimidazo[1,2-b]pyridazine derivatives by palladium cross-coupling and S_NAr reactions is described. Sonogashira and Stille cross-coupling reactions were investigated to introduce alkynyl, alkenyl, and aryl at the 3-position of imidazo[1,2-b]pyridazines. Then, at the 6-position, palladium-catalyzed N-arylation and direct S_NAr were used to introduce amines and alcohols.     

Transition metal-free amination of aryl halides—A simple and reliable method for the efficient and high-yielding synthesis of N-arylated amines

A simple and reliable reaction protocol for the clean, fast, and high-yielding synthesis of various N-arylated amines derived from reactions of aryl halides with various (also sterically hindered) amines under transition metal-free reaction conditions is presented. Dioxane and KN(Si(CH₃)₃)₂ were found to be the ideal solvent and base for this transformation. The conversion rates and yields observed are excellent and in the majority of the reactions performed significantly higher than that obtained in their catalyzed versions. Furthermore, the selective synthesis of 6-halopyridin-2-amines and asymmetric pyridine-2,6-diamines (derived from consecutive reactions of 2,6-dibromopyridine and 2,6-dichloropyridine, respectively, with different amines) is possible in almost quantitative yields (relative to 2,6-dihalopyridine) within very short reaction times. Purification of the 6-halopyridin-2-amine intermediates is not necessary, allowing the synthesis of pyridine-2,6-diamines in ‘one-pot’. However, catalysts are in many cases not required to efficiently and selectively couple aryl halides with amines, making transition metal-free versions of the Buchwald-Hartwig reaction extremely attractive for the synthesis of N-arylated amines with substrates containing substituents on the aryl halide, which either promote regioselectivity and/or do not require regioselective aminations.     

New routes for the synthesis of fused pyrrole scaffolds through transition metal-free tandem reactions

A series of transition metal-free tandem reactions for the synthesis of indolizines and 6,7-dihydroindolizin-8(5H)-ones by 4-bromobut-2-enoate ramifications reacted with 2-acetyl pyrrole derivatives are described. As the α-carbon changed from CH₃, CH₂Cl, CHCl₂, to CCl₃, different kinds of tandem reactions were observed. These tandem reactions could be used to synthesize fused indolizine and indolizidine scaffolds under mild and green conditions.     

Intramolecular asymmetric C–H insertion of N-arylalkyl,N-bis(trimethylsilyl)methyldiazoamides mediated by chiral rhodium(II) catalysts. Synthesis of (R)-β-benzyl-γ-aminobutyric acid

The enantio- and site-selectivity of the intramolecular C–H insertion reactions of acyclic N-arylalkyl, N-bis(trimethylsilyl)methyl α-diazoacetamides, and α-carboalkoxy-α-diazoacetamides 1a–g, catalyzed by chiral Rh(II) carboxamidates and Rh(II) carboxylates were studied. In general, the reaction showed good to excellent chemoselectivity. Regioselectivity for most of the reactions was high, but was also found to be influenced by the structure of the diazo substrate and the chiral Rh(II) catalyst employed. The highest enantioselectivity for the reactions catalyzed by chiral Rh(II) carboxamidates was 69% and Rh₂(4R-MEOX)₄ was found to be the most effective. For the chiral Rh(II) carboxylate catalyzed reactions, the highest ee obtained was 75% and Rh₂(S-PTTL)₄ is the optimal catalyst. The method was applied toward the synthesis of a GABA analogue, (R)-β-benzyl-γ-aminobutyric acid.     

Stereoselective allylation reactions of acyclic and chiral α-amino-β-hydroxy aldehydes 3: Total synthesis of (+)-1-epi-castanospermine

Stereoselective allylation reactions of acyclic, chiral α-amino-β-hydroxy aldehydes containing four contiguous stereocenters were conducted. Allylation mediated by MgBr₂?OEt₂ afforded the anti-product. A plausible mechanism of the allylation reaction is also described. The resulting allylation product was used for the total synthesis of (+)-1-epi-castanospermine.     

Practical synthesis and applications of benzoboroxoles

A convenient one-pot synthesis of benzoboroxoles has been developed via the reaction of o-bromobenzyl alcohols with NaH, ⁿBuLi, and B(OⁱPr)₃ followed by acidic hydrolysis. Applications of these benzoboroxoles have been demonstrated in Pd-catalyzed cross-coupling reactions and the protocol has been extended for the synthesis of a chiral benzoboroxole. Exceptionally short synthesis of a potent antifungal agent AN2690 and several of its analogs has also been realized.     

[Ir(COD)Cl]2/tris(2,4-di-t-butylphenyl)phosphite-catalyzed addition reactions of arylboronic acids with aldehydes

[Ir(COD)Cl]₂/tris(2,4-di-t-butylphenyl)phosphite-catalyzed addition reactions of arylboronic acids with aldehydes were described. The Ir(I) catalyst, generated from [Ir(COD)Cl]₂ and tris(2,4-di-t-butylphenyl)phosphite, was an efficient catalyst system for the addition reactions of a variety of arylboronic acids with aromatic and aliphatic aldehydes. The easy availability of the catalyst and good yields make these reactions potentially useful in organic synthesis.     

Microwave enhanced Suzuki coupling: a diversity-oriented approach to the synthesis of highly functionalised 3-substituted-2-aryl/heteroaryl imidazo[4,5-b]pyridines

A modified approach for the synthesis of 3-substituted 2-aryl/heteroaryl imidazo[4,5-b]pyridines utilising palladium catalysed cross-coupling reactions under microwave enhanced conditions has been achieved. utilisation of (A-^taphos)₂PdCl₂-catalysed cross-coupling reactions enables rapid derivatization of this (imidazo[4,5-b]pyridines) pharmaceutically relevant core. This catalytic system is compatible with a broad spectrum of arylboronic acids—electron rich, electron poor, and heteroarylboronic acids.     

Microwave-assisted SNAr reaction of 2,4,6-trichloro-1,3,5-triazine for the rapid synthesis of C3-symmetrical polycarboxylate ligands

The microwave-assisted S_NAr reaction of 2,4,6-trichloro-1,3,5-triazine with various unprotected amino acids was developed for the synthesis of C₃-symmetrical polycarboxylate ligands which can be used as structural directing units in metal-organic frameworks. The reactions were performed in water using a domestic microwave oven as the heating device. In comparison to the reactions performed under conventional heating, the reactions under microwave irradiation proceeded much more rapidly within 20 min to afford the desired ligands in comparative yields to those obtained by conventional heating.     

Catalytic multimolecular reactions of 1,3-dicarbonyl CH acids with CH<Subscript>2</Subscript>O and <Emphasis Type="Italic">S</Emphasis>- and <Emphasis Type="Italic">N</Emphasis>-nucleophiles

The literature data on the synthesis and properties of oxo-functionalized acyclic and cyclic sulfides obtained by the catalytic multicomponent reactions of 1,3-dicarbonyl compounds with formaldehyde and S-nucleophiles are summarized. An approach to the multimolecular four-component heterocyclization of 1,3-dicarbonyl compounds with CH₂O and S- and N-nucleophiles in the synthesis of sulfanyl-substituted azaheterocycles is discussed.     

Efficient stereospecific synthesis of (S,S)-3-methoxy-4-methylaminopyrrolidine

Efficient stereospecific synthesis of (S,S)-3-methoxy-4-methylaminopyrrolidine, an important intermediate for a novel quinolone antitumor agent AG-7352 is presented. Starting from either d- or l-tartaric acid, a stereospecific synthesis of the chiral pyrrolidine was achieved via two S_N2 displacement reactions. From the results of this synthetic study, the absolute structure of AG-7352 was chemically determined.     

Synthesis of meso-tetraphenyl porphyrins via condensation of dipyrromethanes with N-tosyl imines

A new synthetic route for the synthesis of 5,10,15,20-tetraphenyl porphyrins has been developed based on the reaction of 5-substituted dipyrromethanes with N-tosyl imines in the presence of a metal triflate catalyst. meso-Substituted tetraphenyl porphyrins were synthesized in a two-step process. The first step of the method is the metal triflate-catalyzed condensation of 5-substituted dipyrromethanes with N-tosyl imines to form a porphyrinogen intermediate and the second step is the oxidation of the porphyrinogen to porphyrin. The method was applied to the synthesis of trans-A₂B₂-tetraarylporphyrins and the products were obtained with only a trace amount of one scrambling product. The synthesis of two important building blocks for porphyrin synthesis, mono and di-sulfonamide alkylated 5-substituted dipyrromethanes, was achieved by the addition of 5-substituted dipyrromethane to N-tosyl imine. The application of mono and di-sulfonamide alkylated 5-substituted dipyrromethanes in ‘2+2’ porphyrin formation reactions is presented.     

Chiral bidiaziridines by a two-step domino aziridination of meso-α-diimines

Chiral racemic α-diimines, tested in aziridination reactions with NsONHCO₂Et, for the first time led to the synthesis of (±)-bidiaziridines, stereoselectively derived from the corresponding meso (E-s-trans-E)-α-diimines. Moreover, a minor bidiaziridine isomer, probably a meso form that was lost under classical work-up conditions, can be obtained by adding water to the crude mixtures at the end of amination reactions. The results definitively prove that the imine aziridination by carbamates is a two-step domino process. The structures of the compounds were determined using 2D NMR on purified bidiaziridines.     

Total synthesis of the marine polypropionates,siphonarienal, siphonarienone,and pectinatone

The synthesis of the marine natural products, siphonarienal, siphonarienone, and pectinatone is described employing desymmetrization strategy to create three consecutive stereogenic centers. The key intermediate 7 was made by asymmetric hydroboration of the known meso-olefin using (?)-IPC₂BH followed by PCC and Baeyer-Villiger oxidation reactions.     

Pd- and Cu-catalyzed C–H arylation of indazoles

The palladium- and copper-catalyzed C–H arylation reactions of 1H- and 2H-indazoles with haloarenes are described. A PdCl₂/phen/Ag₂CO₃/K₃PO₄ catalytic system is effective for the C–H arylation of 1H- and 2H-indazoles with haloarenes, whereas a less expensive CuI/phen/LiOt-Bu catalytic system is applicable to the C–H coupling of substituted 2H-indazoles and iodoarenes. The utility of newly developed catalyst was demonstrated in the rapid synthesis of YC-1 (an antitumor agent) and YD-3 (platelet anti-aggregating agent). These new reactions represent important direct functionalization tools of indazoles, well-known bioisosteres of pharmaceutically important indole core.     

EtOAc-dispersed magnetic nanoparticles (DMNPs) of γ-Fe2O3 in the single-pot domino preparation of 5-oxo-2-thioxo-3-thiophenecarboxylate derivatives

EtOAc-dispersed magnetic nanoparticles (DMNPs) of γ-Fe₂O₃ represent a straightforward and green catalyst for the rapid three-component synthesis of 5-oxo-2-thioxo-3-thiophenecarboxylate derivatives as rhodanine skeletons via a single-pot domino process. The rhodanines were prepared over magnetic nanoparticles of γ-Fe₂O₃ without any salt or additives. Dispersed nano-γ-Fe₂O₃ have many advantages, such as stability in air, reusability, reactions with high efficiency, simple separation with magnetic external field from mixture reactions, chemical stability, and also low toxicity.     

A chemoenzymatic-RCM strategy for the enantioselective synthesis of new dihydroxylated 5-hydroxymethyl-indolizidines and 6-hydroxymethyl-quinolizidines

A direct method for the synthesis of new azasugars-like compounds has been developed, which involves a new biocatalytic protocol based on the use of a lipase from Candida Cylindracea and of a ionic liquid as reaction medium, to prepare the key C₁-symmetric piperidine precursor. By subsequent application of RCM reactions and OsO₄-catalyzed double bond syn-dihydroxylation, the synthesis of the target compounds could be accomplished in a straightforward and stereocontrolled manner.