Fulvene-6-carboxylate

Attack on Unsaturated Carbon. The annual addition of phosphites to every variety of activated double bond continues. These include nitro-alkenes,9 a/S-unsaturated carboxylic acid derivatives,10 maleimides,11 fulvenes,12 and pyridinium salts.13 The reaction of diethyl phosphite with keten 0,N-, S,N, and Al,AT-acetals has been used to prepare the enamine phosphonates (19).14... 

The enolization constants of carboxylic acids to form enediols are generally still lower than those of ketones. The pAE of acetic acid is about 20.35 Due to the relatively high acidity of 1,1-enediols, the enol content of carboxylate anions is somewhat higher. When the carboxylate is attached to cyclopenta-dienyl, a strong mesomeric electron acceptor, the conjugate acid of the enol, fulvene-l,l-diol, becomes a strong acid, pAa = 1.3, and the pAE of the enol anion is reduced to 5.0 (Almstead JIK and Wirz J, Unpublished data).36,37... 

In the reaction of sodium methoxide with 3-trichloromethylpyridine the nicotinecarbaldehyde acetal (379 Scheme 69) is formed, whereas by action of methoxide on 2,6-dichloro-3-trichloromethylpyridine the orthoester (380) is accessible.TTie l,l-dichloro-2-acylcyclopropanes on treatment with sodium methoxide undergo ring enlargement to yield the cyclic orthoester (381 equation 178). A mixture of isomeric cyclopentadiene carboxylic orthoacid esters results when the bis(methylthio)fulvene (382 equation 179) is reacted with excess alkoxide. i... 

The same cyclization also succeeds in the absence of a carboxylic group. Heating the fulvene (361), prepared by condensation of o-chlorobenzaldehyde with fluorene, with potassium hydroxide in boiling quinoline leads to benzo(e)acephenanthrylene (J62)127> ... 

Urwyler, B., Wirz, J., The Tautomeric Equilibrium between Cyclopentadienyl 1 carboxylic Acid and Fulvene 6,6 diol in Aqueous Solution, Angew. Chem. Int. Ed. Engl. 1990, 29, 790 792. 

X0 compds. 44, 861 Fulvenes, 6-acoxy- 44, 777 -, 6-siloxy- 44, 777 -, 8-oxy-44, 556 Furan-4-carboxylic acid esters,... 

The 4-1-2- and 8 + 2-cycloaddition reactions of hepta- and penta-fulvenes have been reviewed. The novel intramolecular 4 + 2-cycloaddition of the fulvene (164) yields 6-oxatricyclo[6.4.0.0 ]dodeca-2,l l-diene[4,5-a]naphtho-ennlo 9-carboxylic acid esters (165) (Scheme 63) ... 

Thermal cycloaromatization of enediynes to fulvenes, apparently, is not compatible with systems bearing electron-withdrawing substituents. Thus calculations did not reveal a stable transition state probably due to the high energy required for its formation, hence fulvenes cannot be prepared thermally from the substituted enediynes considered in these calculations. Analysis of the data (BLYP/6G ) showed that the change in reactivity of carbonyl- and carboxyl-containing enediynes is due to the formation of free radicals, which are responsible for the observed cyclizations [7, 316],... 

---