Stoichiometry-controlled cycloaddition of nitrilimines with unsymmetrical exocyclic dienones: microwave-assisted synthesis of novel mono- and dispiropyrazoline derivatives

Abstract

The Microwave-assisted 1,3-dipolar cycloaddition of (E,E)-1,3-bisarylidenetetral-2-ones with nitrilimines affords a series of mono- and dispiropyrazolines in good to excellent yields.

Chemoselective and diastereodivergent synthesis of new spirooxindolo-pyrrolizidines and pyrrolidines stemming from unsymmetrical 1,3-bis(arylidene)tetral-2-ones: a combined experimental and theoretical study

“…1) in accordance with our previous work on ( E , E )-bis(arylidene)tetral-2-ones vis-à-vis nitrilimines. 55 Furthermore, if we depict the QTAIM population results on the optimized ( E , E ) isomer we are able to confirm a discrepancy in the reactivity between its double bonds. Considering the electronic density of the bond critical points values, the DB associated with the 3-position presents a BCP electronic density of about 0.334 a.u., whereas the DB at position 1 reports a lower ρ value in its BCP (about 0.328 a.u.).…”

“…This result is in agreement with our hypothesis as already demonstrated with nitrilimines as 1,3-dipoles that afford spiropyrazolines. 55…”

“…This result is in agreement with our hypothesis as already demonstrated with nitrilimines as 1,3-dipoles that afford spiropyrazolines. 55 Nonetheless, the isolated cycloadducts could be a priori either spiro-3-oxindolopyrrolizidines or spiro-4-oxindolopyrrolizidines.…”

Recent advances in the transition metal-free synthesis of heterocycles from α,β-unsaturated ketones

“…103 The reaction affords the spirocycle 251 in the presence of the catalyst 249 and DABCO in DCM, while the for- Later Gazzeh and co-workers accomplished a Microwave assisted synthesis of mono and dispiropyrazolines (256 and 257). 105 It is a 1,3-dipolar cycloaddition reaction of in situ generated nitrilimines with exocyclic dienones 254 (Scheme 95). The outcome of the reaction is highly controlled by the stoichiometry of the hydrazonyl chloride 255 which is the precursor of nitrilimine.…”

Regioselective Cycloaddition of Nitrile Imines to 5-Methylidene-3-phenyl-hydantoin: Synthesis and DFT Calculations

“…Disubstituted alkenes are typically competent substrates, with trisubstituted olefins reacting more sluggishly [ 9 ]. Nitrile imines are also effectively applied in the cycloaddition reaction with exocyclic alkenes [ 10 ] to form spirocyclic products containing 4-substituted [ 11 ] or 5-substituted pyrazole/pyrazoline cycles [ 12 ]. However, it has been shown that generally intermolecular nitrile imine cycloadditions favors the formation of a regioisomer with the most sterically encumbered substituent of the dipolarophile in the 5-position of the resulting heterocycle [ 13 , 14 ].…”