Die blaßgelben Titelverbindu:ngen (I) und (III) erleiden umkehrbare photochemische konrotatorische elektrocycljsche Reaktionen und liefern in quantitativen Ausb. die dunkelroten bei 100°C stabilen Anhydride (II) bzw. (IV).

Photochromic Heterocyclic Fulgides. Part 4.' The Thermal and Photochemical Reactions of ( E )lsopropyl idene-[a-(2and -(3-t h ienyl)ethyl idene]succinic Anhydrides and Related Compounds

The photochemical rearrangement of (EE)-3,4-photorearrangement of (EE)-3,4-bisarylmethylenedihydro-A photochemical conrotatory ring closure of the furanone (1) followed by a hydrogen shift, would provide a convenient synthesis of apolignans, their derivatives, and related model compounds, allowing structure and stereochemistry to be elucidated, verified, or corrected. Such a reaction would also explain the optical activity of apolignans bisarylmethylenedihydro-2( 3H)-furanones and related 2( 3H)-furanones (1) and related compounds. compounds provide a convenient synthesis of apolignans and their derivatives.FROM our studies on bisarylmethylenesuccinic anhydrides and imides,f,2,3 we suggest that some naturally occurring apolignans and their derivatives4 could be formed by the

Das thermische und photochemische Verhalten der Thiophen‐Derivate (V) und (VI) wird beschrieben [(Vb)‐(Vd) und (VI) werden auf ähnliche Weisewie (Va) synthetisiert].

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