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

Abstract

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 1H 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.

Synthesis and Characterisation of Some Novel Indeno[1,2-c]pyrazoles

“…Had it been the isomeric 2-subsituted-4-phenylindeno[1,2-c]pyrazole (1'a), the signal for C 3 -H should have appeared further downfield at around δ 8.15. This argument finds rationale from earlier observations of Elguero et al 16 who demonstrated that the presence of a heterocyclyl moiety at N2 of the pyrazole ring is responsible for deshielding of the C3-H signal. Moreover, C3-H and C4-H of the indenopyrazole ring system are expected to appear as doublets due to allylic coupling in the case of 2-substituted isomer 1'a rather than two singlets as observed.…”

Structure elucidation and conformational analysis of a fused cyclopentanopyrazolidinol

“…Chim. Acta) instead of the expected 6 dehydration product 2 (Scheme 1). The product 1 showed the presence of a hydroxyl group in the IR 3360 cm 1 and 1 H NMR (5.20 ppm, D 2 O exchangeable) spectra.…”

Synthesis of NewN-(4-Pyridyl)-1-aminopyrazoles and Their Muscarinic and Adrenergic Properties

“…Compounds were detected with UV light (254 nm), iodine chamber, or ninhydrin. Compound 3,5-bis(ethoxycarbonyl)-1H-pyrazole (mp 55 °C) [17] was obtained from diethylazoacetate and ethyl propionate; and 3(5)-methyl-4,5(3)-trimethylene-1H-pyrazole (mp 138 °C) was prepared from 2-acetylcyclopentanone and hydrazine [18] .…”