Synthesis of spiro-1-pyrazolines by the reaction of exocyclic α,β,γ,δ-unsaturated ketones with diazomethane

Abstract

New exocyclic α,β,γ,δ-unsaturated ketones have been synthesized by the base-catalyzed reaction of chromanone, flavanone, their 1-thio analogues and trans-cinnamaldehydes. These unsaturated ketones were reacted with diazomethane at ca. 4 o C to afford spiro-1-pyrazolines in regioselective and stereospecific reaction. Structure and stereochemistry of all these new compounds have been elucidated by combined utilization of various spectroscopic, mainly NMR techniques.

Highly Selective Synthesis of Pyrazole and Spiropyrazoline Phosphonates via Base-Assisted Reaction of the Bestmann–Ohira Reagent with Enones

“…The potential biological properties of pyrazolines such as antifungal, antidepressant, , anticonvulsant, anti-inflammatory, antibacterial, and antitumor properties have been well-recognized. There are sporadic reports of synthesis of spiro-1-pyrazolines by the 1,3-dipolar cycloaddition of exocyclic α,β-unsaturated ketones and diazomethane . Recently, Molchanov et al have reported the synthesis of spiropyrazolines in moderate yield by the addition of diazomethane and ethyl diazoacetate to 2-arylidene-1-tetralones .…”

Potassium Carbonate Assisted Synthesis Of α, β, γ, δ-Unsaturated Ketones

“…The cinnamylideneacetophenones derivatives are key intermediates in organic synthesis for isoquinuclidines [13], 2, 6-diaryl-1,2dihydropyridines [14], spiro-1-pyrazolines [15], (E)-3-styrylchromones [16], 2-benzoyl-1,5diphenylpyrroles [17], 3-aryl-5-styryl-2pyrazolines [18], pentasubstituted cyclohexanes [19], (E)-and (Z)-2-styrylchromones [20], and 3-benzoyl-4-styryl-2-pyrazolines [21]. carried in the absence of a catalyst, the product was not formed ( Table 3, entries 1).…”

Reaction Products of β-Aminopropioamidoximes Nitrobenzenesulfochlorination: Linear and Rearranged to Spiropyrazolinium Salts with Antidiabetic Activity

“…Spiropyrazolines, also termed as spirocyclic hydrazine moiety, are rigid asymmetric heterocyclic structures with a chirality axis and with possible centers of chirality C-5 carbon atoms in the most studied 1,2-diazospiro- and 2,3-diazospiropyrazolines or the ammonium nitrogen atom N(+)-5 in 1,5-diazospiropyrazolinium systems ( Figure 1 ).Thus, these compounds exhibit great synthetic potential due to an enantiomeric advantage, regioisomeric composition, reactivity, and tautomeric transformations. Essentially, 1,2- and 2,3-spiro-1-pyrazolines exist as spiro-2-pyrazolines (∆2 isomers) [ 3 ], although, in solutions, they exhibit an equilibrium of the imine and enamine forms [ 4 ]. As we know, the spiropyrazolinium salts with a 1,5-diazaspiro-1-en-5-ium fragment that we obtained via the hydrolysis of 3-(β-heteroamino)ethyl-5-aryl-1,2,4-oxadiazoles and the arylsulfochlorination of β-aminopropioamidoximes exist, under standard conditions, as the ∆2 isomer [ 5 , 6 , 7 , 8 ].…”