Fischer-type ring closur

Fischer-type ring closure Benzofuran ring from O-aryloximes... 

Homophthalic acids have been directly converted into iso-coumarins . Benzofurans can be prepared from 0-aryloximes by a Fischer-type ring closure . 

Fetvadjian s. Ullmann Fischer-type ring closure 22,937 Fission s. Cleavage Flavanone hydrazones... 

Feist pyrrole ring synthesis Fischer-type ring closure Pschorr — diketone —... 

Calculations [28] on the formation of cyclopropanes from electrophilic Fischer-type carbene complexes and alkenes suggest that this reaction does not generally proceed via metallacyclobutane intermediates. The least-energy pathway for this process starts with electrophilic addition of the carbene carbon atom to the alkene (Figure 1.9). Ring closure occurs by electrophilic attack of the second carbon atom... 

Calculations performed for cyclopropanation with Fischer-type carbene complexes [28] indicate that the electrophilic attack of the carbene complex at the alkene and the final ring closure are concerted. Extrapolation from this result to the C-H insertion reaction (in which a a-bond instead of a 7i-bond is cleaved) suggests that C-H bond cleavage and the formation of the new C-C and C-H bonds might also be concerted (Figure 3.38). 

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