Gyoergy Keglevich

d-Glucose-based azacrown ethers with a phosphonoalkyl side chain: application as enantioselective phase transfer catalysts

Abstract Five chiral α- d -glucose-based monoaza-15-crown-5 ethers with a phosphonoalkyl side chain 5a – e have been synthesized. The substituent at the nitrogen atom has a major influence on the cation extraction ability of the azacrown. The new lariat ethers 5a – e show significant asymmetric induction as phase transfer catalysts in the Michael addition of 2-nitropropane to chalcone.

Efficient Synthesis of Phosphono‐ and Phosphinoxidomethylated N‐Heterocycles under Solvent‐Free Microwave Conditions

Abstract Simple N‐heterocycles were converted to N‐phosphono‐ and phosphinoxidomethyl derivatives by a solvent‐free microwave‐assisted condensation of the heterocycle, paraformaldehyde, and diethylphosphite or diphenylphosphine oxide in a convenient and, in most cases, efficient way. In contrast to an earlier report, imidazole proved to be unreactive in this type of phospha‐Mannich reaction.

Microwave irradiation as an alternative to phase transfer catalysis in the liquid-solid phase, solvent-free C-alkylation of active methylene containing substrates

Simple CH-acidic compounds can be easily monoalkylated in solid-liquid phase in the absence of a phase transfer catalyst applying microwave under solvent-free conditions.

Advances and New Variations of the Hirao Reaction

Introduction ................................................................................. 282 1. Coupling of Aryl Halides or Other Aryl Derivatives with Dialkyl Phosphites, Secondary Phosphine Oxides and Related Derivatives in the Presence of Pd(0) P Complexes........................ 282 2. Couplings in the Presence of Catalysts Formed from Pd(II) Salts and P-ligands ................................................................................ 290 3. “Greener” Accomplishments......................................................... 300 4. Couplings in the Presence of Cu and Ni Salts ................................ 303 5. Forming P C Bonds via the Salts of the >P(O)H Reagent ............. 307 6. Conclusions .................................................................................. 311 References .................................................................................... 311

Microwave‐Promoted Efficient Synthesis of 2‐Phosphabicyclo[2.2.2]octadiene‐ and Octene‐2‐oxides under Solvent‐Free Conditions in Diels–Alder Reaction

Abstract The microwave‐induced and solvent‐free Diels–Alder reaction of 1,2‐dihydrophosphinine oxides (1 and 5) and dimethyl acetylenedicarboxylate or N‐phenylmaleimide afforded 2‐phosphabicyclo[2.2.2]octadiene‐ (2 and 6) and phosphabicyclo[2.2.2]octene oxides (4 and 7), respectively, almost quantitatively and in a fast reaction in an ecofriendly manner.

A “green” variation of the Hirao reaction: the P–C coupling of diethyl phosphite, alkyl phenyl-H-phosphinates and secondary phosphine oxides with bromoarenes using a P-ligand-free Pd(OAc)2 catalyst under microwave and solvent-free conditions

The P–C coupling of diethyl phosphite, alkyl phenyl-H-phosphinates, diphenylphosphine oxide and dialkylphosphine oxides with bromoarenes may be performed in the presence of a P-ligand-free Pd(OAc)2 catalyst and triethylamine under microwave-assisted (MW) and, in almost all cases, solvent-free conditions to afford diethyl arylphosphonates, alkyl diphenylphosphinates, aryldiphenylphosphine oxides and dialkylphenylphosphine oxides, respectively. This is the “greenest” accomplishment of the well-known Hirao reaction that has now been found to have general application for a broad spectrum of >P(O)H species with different reactivity and a great variety of substituted bromobenzenes. The alkyl phenyl-H-phosphinates were prepared by the MW-promoted alkylation of phenyl-H-phosphinic acid in the absence of any solvent.

Microwave-assisted solid-liquid phase alkylation of naphthols

Abstract: The microwave promoted alkylation of 1- and 2-naphthols with benzyl, butyl, ethyl and isopropyl halides in the presence of an alkali carbonate may result in O- and C-alkylated products. The alkylations were O-selective in the presence of K2CO3 in acetonitrile as the solvent and in the absence of phase transfer catalyst. The alkylations utilizing butyl and ethyl halides were also O-selective in solventless accomplishment and in the presence of triethylbenzylammonium chloride

Practical Synthesis of 6-Chloro-dibenzo[c.e][1,2]oxaphosphorine

Abstract The title P-heterocycle 3, a versatile intermediate in synthesis, was prepared by two independent methods. The first involves an environmentally friendly version of an old protocol starting from 2-phenylphenol (1) and phosphorus trichloride. Their interaction could be accomplished at 50 °C under solventless conditions. Cyclization of the intermediate (2) so obtained could be realized best under microwave conditions at 150 °C in the presence of ZnCl2. This method offers advantages over the traditional ones. According to another approach, the chloro-dibenzooxaphosphorine (3) was obtained by the novel reaction of 6H-dibenzo[c.e][1,2]oxaphosphorine-6-oxide (4) with phosphorus trichloride in boiling chloroform. Efficiency of the syntheses was demonstrated by converting the crude product 3 to a more stable phosphonic amide (6) that was stable enough to be isolated.

Catalytic Transfer Hydrogenation and Hydrogenolysis in Ionic Liquids with Pd/MgLa Mixed Oxide and Pd/MgAl Hydrotalcite as Recyclable Catalysts

Abstract A new Pd/MgLa mixed oxide and the known Pd/MgAl hydrotalcite catalysts were applied and recycled successfully in catalytic transfer hydrogenation reactions in ionic liquids. Some α,β‐unsaturated carboxylic acid derivatives were hydrogenated in excellent yields. The catalysts were recycled without significant loss of activity. Besides that, a number of halogenated aromatic compounds were dehalogenated under similar catalytic transfer conditions.

The synthesis of phosphinates : traditional versus green chemical approaches

Abstract Three alternatives are discussed in comparison with the classical esterification of phosphinic chlorides by reaction with alcohols. All novel methods, such as microwave (MW)-assisted direct esterification, MW-assisted phase transfer catalyzed alkylating esterification and the propylphosphonic anhydride-promoted esterification, start from phosphinic acids and offer different advantages and disadvantages. The methods are analyzed from green chemical point of view.