LINK synthesis with 3-hydroxy-1H-pyrazoles: 3-carboxyisoalkyloxy-1H-pyrazoles-bicyclic acylpyrazolium salts and γ-lactams-3-carboxyisoalkyloxy-4,5-dihydro-1H-pyrazol-5-ones

Article abstract of DOI:10.1002/prac.19983400506

1-Substituted 3-hydroxy-1H-pyrazoles 1 react with chloroform, NaOH, and aceton resp. butan-2-one O-regiospecifically to yield 2-methyl-2-[(1H-pyrazol-3-yl)oxy]-propanoic resp. -butanoic acids 14 via a dichlorocarbene (12)-dichlorooxirane (9) pathway. Chlorides 17 of 14 easily cyclize to N-acylpyrazolium salts 18/19, which quantitatively afford esters 22-26 and amides 27-29 of 14. Enantiomers of the butanoic acid 14h, obtained via their diastereomeric cholesterol esters, differ in their stimulus to peroxisome proliferation. At 140°C pyrazolium salts 18 undergo thermolysis to bicyclic β-oxa-γ-lactams 30-32. 3-Carboxyisoalkylamino-pyrazoles similarly give 1H-β-aza-γ-lactams 34. Reactions of 14 with surplus SOCl₂ result in 6-chloro-37 resp. 7-chloro-β-oxa-γ-lactams 38 via chlorosulfinylation and extrusion of SO, and in 4,4-bispyrazolyl-sulfoxide 39. A mild introduction of additional O-functions into pyrazoles affording 4,5-dihydro-3-hydroxy-5-oxo-1H-pyrazoles 52-57 is presented. Biological effects of the new pyrazoles are protection against shock and ADP-induced thromboembolism, reduction of serum lipids and improvement of blood flow. Johann Ambrosius Barth 1998.