Ylide pyrazolidinium

Stable heterocyclic five-member azomethine imines, azolium fV-imides, tria-zolium and pyrazolidinium ylides 98H(49)587. 

The 3-oxo-2-pyrazolidinium ylides 315, easily available by reaction of the corresponding pyrazolidin-3-one with aromatic aldehydes, function as 1,3-dipoles in cycloaddition reactions with suitable alkenes and alkynes to provide the corresponding products. When unsymmetrical alkynes are used, mixtures of both possible products 316 and 317 are usually obtained (Equation 45). The regioselectivity of cycloadditions of the reaction with methyl propiolate is influenced by the substituents on the aryl residue using several 2,6-di- and 2,4,6-trisubstituted phenyl derivatives only compound 316 is formed <2001HCA146>. Analogous reactions of 3-thioxo-l,2-pyrazolidinium ylides have also been described <1994H(38)2171>. 

Compound 318 used as dipolarophile with ylide 315 (Ar = 2,4,6-Me3C6H2) gives spiro compound 319 (Equation 46) <2001HCA3403>. The 1,3-dipolar cycloaddition of 3-oxo-2-pyrazolidinium ylide 315 (Ar = Ph) with buckminsterfullerene Cgo yields new heterocyclic fullerene derivatives <1995TL2457>. 

Organosilicon compounds have also been reacted with thiocarbonyl ylides to afford a variety of heterocycles468,469 and in Section III.F.5 we pointed out the 1,3-dipolar cycloaddition between in situ generated thioaldehydes and a pyrazolidinium ylide to produce a nuclear analogue of pyrazolidinone antibacterial agents332. Moreover, Vedejs has applied the dipolar cycloaddition between a thione, generated from a Norrish-type II fragmenta-... 

Various other [3 + 2] cycloadditions, affording chiral, anellated C6o derivatives with stereogenic centers in the addends are reported in literature. The products were generally obtained as racemates and resulted from reaction of buckminsterfullerene with species like 2,3-disubstituted 2//-azirincs (via nitrile ylides [under direct irradiation] or via 2-azaallenyl radical cations [sensitization by photoinduced electron transfer]),365 1-substituted 5-diazopentane-1,4-diones (via cyclic carbonyl ylides),366 7-alkylidene-2,3-diazabicyclo[2.2.1] hept-2-ene (via a diradicaloid trimethylenemethane derivative),367 1-benzylpy-razolidine-3-ones in the presence of aldehydes (via pyrazolidinium ylides),368 2-trifluoromethyl-2,5-dihydro-l,3-oxazol-5-ones (via nitrile ylides),369 nitro-alkanes in the presence of triethylamine and trimethylsilyl chloride (via N-silyloxynitrones),370 or dv-HOCH2 CH=C H C H 2 OCO 2 H( in the presence of... 

Jungheim, L.N., and Sigmund, S.K., 1,3-Dipolar cycloaddition reactions of pyrazolidinium ylides with acetylenes. Synthesis of a new class of antibacterial agents, J. Org. Chem., 52, 4007, 1987. 

A first approach towards bicyclic pyrazolidinones [108, 109] used 1,3-dipolar cycloaddition of pyrazolidinium ylides to acetylenic compounds as a key step. The reaction of ylide 211 [110] with allyl acetylenedicarboxylate yielded 212 from which the diacid 213 was readily obtained (Scheme 60). This compound exhibits weak in vitro antimicrobial activity against S. aureus. 

The Strategy above suffered from a lack of regiocontrol in the cycloaddition step. A modification [113] used vinyl sulphones 222 which reacted regio-selectively with pyrazolidinium ylide 218 to give the cycloadducts 223 (Scheme 64). Base-catalysed elimination of benzene sulphinic acid led to the desired bicyclic pyrazolidinones 220a to d. These compounds could also be prepared without racemisation from the optically pure pyrazolidinone 216, derived from L-serine [114]. 

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See also in sourсe #XX -- [ , ]

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