First quinine-based aryl phosphite: synthesis and application in the Pd-catalyzed enantioselective rearrangement of allylic thiocarbamate

New quinine-based polyfunctional aryl phosphite was synthesized. The phosphorus center in the new compound is characterized by a large cone angle ( = 190°). The new compound can be used in the Pd-catalyzed enantioselective rearrangement of cyclic O-allylic thiocarbamate into S-allylic thiocarbamate in an optical yield of up to 47% with a quantitative conversion.     

Pd-catalyzed copper-free carbonylative Sonogashira reaction of aryl iodides with alkynes for the synthesis of alkynyl ketones and flavones by using water as a solvent

The Pd-catalyzed copper-free carbonylative Sonogashira coupling reaction to synthesize alkynyl ketones from terminal alkynes and aryl iodides was achieved by using water as a solvent. The reaction was carried out at room temperature under balloon pressure of CO with Et(3)N as a base. The developed method was successfully applied to the synthesis of flavones.     

New efficient preparation of arylzinc compounds from aryl halides using cobalt catalysis and sacrificial anode process

Electroreduction of aryl-chlorides or -bromides in an electrochemical cell fitted with a sacrificial zinc anode and in the presence of cobalt halide associated with pyridine as ligand in DMF or acetonitrile as solvent affords the corresponding organozinc species in good yields.     

Stereodivergent synthesis of 1,4-bifunctional compounds by regio- and diastereoselective Pd-catalyzed allylic substitution reaction

Highly stereoselective synthesis of 1,4-bifunctional compounds was accomplished via 1,2-asymmetric induction to α-oxyaldehyde and α-oxyketone followed by regio- and diastereoselective Pd-catalyzed allylic substitution reaction. We found that trifluoroacetate is a suitable leaving group for the allylic substitution reaction. Various nucleophiles containing carbon, nitrogen, and sulfur can be applied to the method. Both 1,4-syn- and 1,4-anti-adducts were synthesized with high stereoselectivity by using stereodivergent reduction of the propargyl alcohols followed by allylic substitution reaction.     

Novel route to azobenzenes via Pd-catalyzed coupling reactions of aryl hydrazides with aryl halides,followed by direct oxidations

[reaction: see text] N-Boc aryl hydrazines undergo Pd-catalyzed coupling reactions with aryl halides to provide N-Boc diaryl hydrazines in excellent yields. The resulting N-Boc diaryl hydrazines were directly oxidized with NBS/pyridine in CH(2)Cl(2) at room temperature to the azobenzenes.     

Mechanism of the electrochemical conversion of aryl halides to arylzinc compounds by cobalt catalysis in DMF/pyridine

The study of the electrochemical behavior of cobalt bromide, CoBr2, in the presence of zinc bromide, ZnBr2, and aryl halides, ArX, in a dimethylformamide (DMF)/pyridine (9:1, v/v) mixture allowed us to complete the study of the mechanism of the electrochemical conversion of aryl halides into arylzinc compounds by using cobalt catalysis. The last step of the catalytic process has been shown to be a transmetalation reaction between the arylcobalt(II) species and zinc ions that regenerates the cobalt(II) catalyst. The effect of zinc bromide on each step of the catalytic cycle has been studied. It is especially shown that the presence of ZnBr2 stabilizes the electrogenerated Co1 but has no effect on the rate constant of the oxidative addition of aryl halides, ArX, to Co1. Rate constants for the disproportionation reaction of Co1 and the oxidative addition have been determined in the presence of ZnBr2 and compared with the values obtained in its absence.     

Cleavage of the ethereal bond : XI. The reaction of allylic organomagnesium halides with 1,3-benzoxathiole and 1,3-benzodioxole

Some reactions of 1,3-benzoxathiole and 1,3-benzodioxole with allylic Grignard reagents have been examined and found to give cleavage of the ether bond to form substitution products with almost complete allylic rearrangement.     

Selective synthesis of monoorganotin trihalides: the direct reaction of allylic halides with tin(II) halides catalyzed by platinum and palladium complexes

The reaction of 3-haloalkenes (3-chloropropene, 3-bromopropene, 3-chloro-2-methylpropene, 1-chloro-2-butene) with SnX₂ (X=Cl, Br) to form mono-allyltin trihalides, was catalyzed by several platinum and palladium complexes of the type MZ₂L (M=Pt, Pd; Z=Me, Cl; L=2,2′-bipyridine, 1,10-phenanthroline or dppe). The highest yield of allyltin trichloride was obtained for the reaction of 3-chloropropene with SnCl₂ catalyzed by PdMe₂(phen) (83%) while the yield obtained with the other catalysts decreased in the order PdCl₂(phen), PdCl₂(bipy)>PdMe₂(bipy)>PtCl₂(phen)>PtMe₂(bipy)>PtMe₂(phen)>PtCl₂(bipy). Interestingly, PdCl₂(PhCN)₂ and Pd(PPh₃)₄ had no activity at all. The yield of allyltin trichloride was not only dependent on the activity of the catalyst but also on the decomposition rate of the product in the presence of the catalyst. 3-Bromopropene gave 19% of allyltin tribromide when reacted with SnBr₂. The other 3-haloalkenes did react but the resulting monoallylictin trihalides were not stable enough to produce significant yields. Reaction of both, benzyl chloride and chlorobenzene, led to catalyst decomposition. In addition, SnCl₂ catalyzed formation of polybenzyl was observed in the case of benzyl chloride.     

Palladium-catalyzed C-O bond formation: direct synthesis of phenols and aryl/alkyl ethers from activated aryl halides

A simple and efficient palladium-catalyzed carbon-oxygen bond formation is reported. The palladium-tri-tert-butylphosphine complex was found to be effective in converting haloarenes to corresponding substituted phenols. This methodology offers a direct transformation of aryl halides to phenols, as well as the straightforward application to generate a wide variety of diaryl or alkyl/aryl ethers.     

Sequential unsymmetrical aryl coupling of o-substituted aryl iodides with o-bromophenols and reaction with olefins: palladium-catalyzed synthesis of 6H-dibenzopyran derivatives

Dibenzopyran derivatives are prepared by palladium- and norbornene-catalyzed reaction of aryl iodides, o-substituted with electron-releasing substituents, o-bromophenols, and activated alkenes.     

CuI-mediated cross-coupling of aryl halides with oximes: a direct access to O-aryloximes

The first Cu-catalyzed cross-coupling of aromatic oximes and haloarenes is reported. This one-step formation of the =N-O-Ar linkage gives access to a range of oxime ethers in good to moderate yields.     

In situ trapping of Boc-2-pyrrolidinylmethylzinc iodide with aryl iodides: direct synthesis of 2-benzylpyrrolidines

Addition of (S)-(+)-tert-butyl 2-(iodomethyl)pyrrolidine-1-carboxylate to activated zinc, aryl halides, and a catalyst derived from Pd(2)(dba)(3) (2.5 mol %) and SPhos (5 mol %) in DMF allows trapping of the corresponding organozinc reagent, with formation of Boc-protected 2-benzylpyrrolidines (20-72%).     

2,6-Diazaspiro[3.3]heptanes: synthesis and application in Pd-catalyzed aryl amination reactions

A concise and scalable synthesis of a 2,6-diazaspiro[3.3]heptane building block is reported. The usefulness of this structural surrogate of piperazine is shown in arene amination reactions yielding a variety of N-Boc- N'-aryl-2,6-diazaspiro[3.3]heptanes.     

Pd-catalyzed cross-coupling of allylsilane-vinylcopper species with aryl and vinyl halides: the first total synthesis of (−)-nomadone

The reaction of allene with a lower order silylcuprate 3 leads to an allylsilane-vinylcopper intermediate 4, which undergoes palladium-catalyzed cross-coupling reaction with both vinyl and aryl halides. The influence of several factors such as the nature of the transition metal used as catalyst, the temperature of the reaction, and the order of addition are studied. This simple methodology allows the synthesis in one step of isoprenylsilanes, which can be conveniently coupled with different isoprenic aldehydes to give several acyclic natural terpenes. Thus, we were able to synthesize, in two steps from allene, the natural monoterpenes (±)-ipsdienol and (±)-ipsenol, which are the principal components of the aggregation pheromone of the bark beetle Ips paraconfusus. On the other hand, the allyl-terminated reaction of isoprenylsilane 7 with the natural monoterpene (S)-citronellal leads to an intermediate, which is readily converted into the natural sesquiterpene (−)-Nomadone in two almost quantitative steps. The nomadone sesquiterpene is a component of the cephalic gland's secretion of Nomada bees. As far as we know this is the first reported total synthesis of (−)-nomadone.     

Palladium-catalyzed coupling reaction of terminal alkynes with aryl iodides in the presence of indium tribromide and its application to a one-pot synthesis of 2-phenylindole

The use of a novel PdCl(2)(PPh(3))(2)-InBr(3) reagent system to catalyze cross-coupling reactions of a variety of aryl iodides with several terminal alkynes is described. The corresponding functional alkyne derivatives were produced in good to excellent yields. Moreover, a catalytic amount of InBr(3) effectively catalyzes the intramolecular cycloaddition of 2-phenylethynylaniline to form an indole skeleton in high yield.     

The palladium-catalyzed reaction of aryl iodides with mono and disubstituted acetylenes: a new synthesis of trisubstituted alkenes.

Mono and disubstituted acetylenes react with aryl iodides containing a variety of functional groups in the presence of palladium catalyst, formic acid and a tertiary amine to give trisubstituted alkenes.