Cyclopropenone 1,3-propanediyl ketal

Chloro-l, 3-butadiene, 71 Cyclopentadiene, 78 Cyclopropenone 1,3-propanediyl ketal,... 

Cyclopentenes Benzy chlorobis(triphenyl-phosphine)palladium( lI). Cyclopropenone 1,3-propanediyl ketall. Di-p,-carbonylhexa-carbonyldicobalt. 

CYCLO ADDITION N-Alkylhydroxy-lamines. f-Butyldimethylsilyl ethylnitron-ate. Cyclopropenone 1,3-propanediyl ketal. Hydrogen peroxide-Sodium tungstate. N-Methylhydroxylamine. Phenyl isocyanate. Trimethylamine N-oxide. Trimethylsi-lylmethyl azide. 

The addition of cyclopropenone 1,3-propanediyl ketal to electron deficient olefins produces cyclopentanone ketals 4,4,5-trisubstituted 3,3-[l,3-propanediylbis(oxy)]cyclopentenes 1 in 42-86 % yield with high regioselectivitv. Presumably diradicals or zwitterions are not involved as reactive intermediates, and the reaction starts with nucleophilic attack of the strained cyclopropene olefin onto the electron-deficient olefin2. 

A solution of (Z)-benzyl methyl (phenyl methylene) malonate 2 (Z) (120 mg, 0.405 mmol) in MeCN-da (0.4 mL) was treated with cyclopropenone 1,3-propanediyl ketal 1 (132 mg, 1.18 mmol, 2.9 equiv) under N2. After 20 h heating at 80°C (shielded from light), the cooled mixture was concentrated in vacuum, and the residue filtered through a short column of SiOa (CH2CI2). Evaporation of the solvent and chromatography (Si02 CH2CI2) afforded 8 mg of 2 (recovered), 1 (recovered) and a mixture of 3 (99 mg, 60%). Ratio cis trans 90 10. 

---