Synthese und Eigenschaften von 3-Acylmethylen -2-(2-hydroxy-1-alkenyl)-1-phenylcyclopropen, einer neuartigen Klasse von stabilisierten Triafulvenen

Cyclopropenylium Cations, Cyclopropenones, and HeteroanaloguesRecent Advances

“…Fluorine is a strongly electronegative substituent, but it is also a π-electron donor. Experimental geometry, obtained by microwave spectra for 16 O and 18 O isotopomers, and ab initio calculations indicated that difluorocyclopropenone has a resonance energy comparable to that of parent cyclopropenone.…”

“…One representative highly symmetrical structure of 19c was determined by X-ray crystallography (Figure 1). 16 One of the recent reactions to be noted for the combination of a C 1 unit to a C 2 unit is represented by the synthesis of tris(trimethylsilyl)cyclopropenylium cation (23), as shown in eq 9. 17 Thus, either a Cu(I)-catalyzed thermal reaction or a photochemical reaction of bis(trimethylsilyl)acetylene with diazoacetate 20 afforded cyclopropenecarboxylate 21, which was hydrolyzed and transformed to the first cyclopropenylium cation fully substituted with silicon, 23, by treating the cyclopropenecarbonyl chloride 22 with SbCl 5 .…”

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1 X-ray crystal structure of 19c . [Reprinted with permission from ref . Copyright 2002 Georg Thieme Verlag.

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“…When 1,2-dichloro-3-phenylcyclopropenylium cation ( 17 ) was allowed to react with 2 equiv of silylenol ether 18 , novel triafulvene derivatives, 19 , having a cyclic “7-hydroxy-2,4,6-heptatrien-1-one”-type structure with intramolecular hydrogen bonding were obtained in 32−78% yield (eq 8). One representative highly symmetrical structure of 19c was determined by X-ray crystallography (Figure ) …”

Recent Advances in Cyclopropene Chemistry

“…Likewise, treatment of monoarylated salt 45 with silyl enol ethers 46 gave access to triafulvenes 47, which are additionally stabilized by intramolecular hydrogen bonding (Scheme 32). 70 Scheme 32…”