Konrad Krolikiewicz

A simple synthesis of Δ2-oxazines, Δ2-oxazines, Δ2-thiazolines and 2-substituted benzoxazoles

Abstract Carboxylic acids react readily at O°→+24°C with amino alcohols, amino mercaptans and o-aminophenols in the presence of triphenylphosphine- or tributylphosphine dichloride (generated in situ from the reaction of the phosphines with hexachloroethane or CCl4) and triethylamine in acetonitrile to form the corresponding Δ2-oxazolines, Δ2-oxazines, Δ2-thiazolines and 2-substituted benzoxazoles in one reaction step in yields of up to 80%.

A simple synthesis of Δ2-oxazolines, Δ2-oxazines, Δ2-thiazolines and Δ2-imidazolines

Abstract Carboxylic acids react with amino alcohols, amino mercaptans or diamines in the presence of triphenylphosphine, CCl4 and tert. bases to afford in 50–75% yield the corresponding Δ2-oxazolines, Δ2-oxazines, Δ2-thiazolines and Δ2-imidazolines.

The introduction of nitrile-groups into heterocycles and conversion of carboxylic groups into their corresponding nitriles with chlorosulfonylisocyanate and triethylamine

Abstract Addition of chlorosulfonylisocyanate (CSI) to heterocycles such as thiophene ( 4 ) or indole ( 15 ) and unsaturated systems such as dihydropyran ( 7 ) gives N-chlorosulfonylamides RCONHSO 2 Cl, which can be converted by equivalent amounts of triethylamine to their corresponding nitriles. Since carboxylic acids react with CSI to N-chlorosulfonylamides, subsequent treatment with triethylamine affords the corresponding nitriles, but no isocyanates as claimed by other authors. The mechanisms of the conversion of the intermediate N-chlorosulfonylamides into the corresponding nitriles are discussed.

A new simple nucleoside synthesis

Abstract Persilylation of excess D-ribose or D-glucose with 6-azauracil or N -benzoyladenine followed by condensation with trimethylsilyl triflate in acetonitrile at 80° affords the corresponding persilylated nucleosides. Transsilylation with methanol and chromatography on SiO2 give the pure free nucleosides in up to 70% yield.

The Synthesis of 2-Fluoropurine Nucleosides

Abstract 2-Aminoadenosine, obtained by silylation-amination from guanosine, is readily converted by KNO2/ HF/Pyridine in up to 80% yield into 2-fluoradenosine, which is a convenient starting material for the preparation of 9(β-D-arabinofuranosyl)-2-fluoroadenine 5′-phosphate (Fludara). N6N6-Pentamethylene-2-aminoadenosine and guanosine afford likewise the corresponding 2-fluoropurine nucleosides in high yields.

A simple reduction of aromatic heterocyclic N-oxides with hexamethyldisilane: reactions with hexamethyldisilane and fluoride ion I

Abstract Aromatic heterocyclic N-Oxides are readily reduced at room temperature by hexamethyldisilane in the presence of fluoride ion in THF.

New simple wittig-type cyclizations to flavones, 4-quinolones and indenones

Abstract 2-Acyloxy-, 2-phthalimido- or 2-benzoylbenzoic acids 4 , 6 and 9 are readily cyclized in one step in up to 80% yield by excess triphenylphosphine/carbon tetrachloride in methylene chloride at 24°C to the corresponding 3-chloroflavones 5 , 3-chloroquinoline-4-ones 7 or 2-chloroindenones 10 . On employing trichloroacetonitrile instead of carbon tetrachloride and subsequent heating to 180°C 2-acetoxy-benzoic acid (aspirin) 1 is cyclized to 2 -methyl-3-cyanoflavone 28 .

The Introduction of C-Substitutents into Pyrimidine- and Purine-Nucleosides

Abstract The introduction of C-substituents into pyrimidine and- purine-nucleosides by sulfide contraction [compare Ang. Chem. 88, 724 (1976), Int. Ed. 15 689 (1976)] will be discussed with the emphasis on unpublished work.