Detalle de: Synthesis and NMR spectroscopy ( 1 H 13 C) of 1-(2′-benzothiazolyl)-3(5),4-polymethylenepyrazoles and related compounds

A series of 3(5),4‐trimethylene and 3(5),4‐tetramethylenepyrazoles (tetrahydroindazoles) have been prepared from 2‐acylcyclanones using two methods: direct reaction with a substituted hydrazine and through an NH‐pyrazole followed by nucleophilic substitution. The results mainly concern the 2‐benzothiazolyl substituent, but 2,4‐dinitrophenyl derivatives were also studied for comparison. The orientation of the reactions (isomer ratio), the deshielding in 1 H nmr of the 5‐methyl and 5‐methylene signals when a benzothiazolyl residue is at position 1, and the ring strain effect on heterocyclic carbons chemical shifts, are discussed.