1, 1′-Bi-(2-aryl-1, 2-dihyrophthalazinylidenes): potential new pigment. Relief of strain by a trans-folded alkene linkage

…, AM Gillan, P McArdle, D Cunningham

Index: Butler, Richard N.; Gillan, Ann M.; McArdle, Patrick; Cunningham, Desmond Journal of the Chemical Society, Chemical Communications, 1987 , # 13 p. 1016 - 1017

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Abstract

Six-membered heterocyclic ylidenes are a remarkably rare the five-membered heterocyclic analogues, such as indigo, class of compounds.1J The lack of examples was earlier which are more common. In strained five-membered ylidenes ascribedl to possible increased-steric hindrance between the the double bond is twisted out of planarity (I) and for example six-membered rings at each end of the alkene unit relative to the torsional angle in 9,9'-bifluorenylidene is ...