Cyclopentane Hydrazine

Oxindoles can be prepared from N,p-acvlphcnyl hydrazines by a reaction which is analogous to the Fischer cyclization. This is known as the Brunner reaction. The reaction is typically conducted under strongly basic conditions. For example, heating N-phenylcyclopentanecarbonylhydrazide with CaO gives a 70% yield of spiro-cyclopentane oxindole[l]. 

The catalytic asymmetric hydroboration reaction can also be applied to OTei o-bicyclic hydrazines. The resulting alcohols are of great synthetic interest and can lead to cyclopentanic diamino alcohols with good enantiomeric purity (equation 14). Interestingly, a reversal of enantioselectivity is observed between reactions employing rhodium and iridium catalysts. ... 

Reactions of cyclic and acyclic 1,2,3-triones with phenylhydrazine give rise to mono- and bis-(phenylhydrazones). The central carbonyl group of a vicinal tricarbonyl system is electron-deficient and highly electrophilic,255 which is why treatment with an aryldiazonium ion affords 2-phenylhydrazones. The structure of such bis(phenylhydrazones) as cyclopentane-1,2,3-trione 1,3-bis(phenylhydrazone), dehydroascorbic acid 2,3-bis(phenylhydrazone), and cy-clobutanetetraone l,3-bis(phenylhydrazone) has been studied by UV, IR,1H-, 13C-, and 15N-NMR spectroscopy.265-268 Quantum-mechanical calculations to predict the most stable tautomeric forms of some 1,2- and l,3-bis(phenylhydrazones) revealed that the chelated bis(hydrazone) structure was usually more stable than the azoene-hydrazine structure.269-271 This does not mean that such structures do not exist, for example cyclobutanetetraone l,2,3-tris(phenylhydrazone) exists in a stable phenylazoene-hydrazine structure (see 49 Scheme 8).257-263... 

Seven-membered Rings.—Whereas pyrolyses of 5-acetoxymethylcycloheptene at 350 °C in a flow system gave mixtures of bi- and tri-cyclic products, pyrolysis in a sealed tube gave a mixture of 5-methylenecycloheptene and l-methylene-3-vinyl-cyclopentane. " Reactions of cyclohepta-2,6-dienone with substituted hydrazines, hydroxylamines, and carbohydrazines, gave the adducts (217). ... 

---