Benzoloxid-Oxepin-Valenztautomerie

Cyclic sulfides in organic synthesis

Synthesis and antifungal activity of some 3-benzylidenechroman-4-ones, 3-benzylidenethiochroman-4-ones and 2-benzylidene-1-tetralones

Publisher Summary This chapter discusses aromaticity of heterocycles. At a time when the validity of the concept of aromaticity is questioned, increasingly, it seems appropriate to review various definitions in common use and to survey their applications in heterocyclic chemistry. From a qualitative viewpoint the characteristics of an aromatic compound are easy to define. A compound is said to be aromatic if it is cyclic and unsaturated with an enhanced stability over simple olefinic compounds. The characteristic aromatic reactivity of the type described is clearly a matter of degree and is difficult to assess quantitatively. From a simple consideration of pyridine, which reacts less readily with electrophiles but more readily with nucleophiles at the ring carbon atoms than does benzene, it soon becomes apparent that attempts to discuss even relative aromatic character using kinetic criteria is fraught with difficulties; this is apart from the fundamental objection that chemical reactivity is not solely a function of ground-state stability.

Aromaticity of Heterocycles

Publisher Summary This chapter focuses on thiochromanones and related compounds. The scarcity of reviews and recent interest in thiochromanones and related compounds calls for a comprehensive summary of this area of heterocyclic chemistry. The apparent similarity between these systems and the naturally occurring chromanones, chromones (flavones), chromenes, etc., is responsible for the continued importance of these sulfur heterocycles. The focus is directed to five ring systems: Thiochromans, thiochromones, isothiochromans, benzothiopyrans, and benzothiopyrylium salts. It is completely difficult to segregate their chemistry since they are so interrelated; cross-references will be employed as often as possible. Thiocoumarins and thioxanthones are excluded since these molecules differ considerably from those reviewed here. The chapter discusses about thiochromans, thiochroman-4-ones, and thiochromones. isothiochromans and isothiochromanones have also been discussed in the chapter. The chapter closes with a discussion on benzothiopyrans and benzothiopyrylium salts.

Thiochromanones and Related Compounds

Durch Umlagerung von 3.α-Epoxy-3-benzyl-chromanonen-(4), 3.α-Epoxy-3-benzyl-1-thiochromanonen-(4) und von 3.α-Epoxy-3-benzyl-1-thio-chromanon-(4)-1.1-dioxiden (1–5, 1316) wurden 4-Aryl-2.3.4.5-tetrahydro-1-benzoxepin-dione-(3.5) und die analogen Verbindungen mit Sulfid- bzw. Sulfonfunktion erhalten (18–22, 23–26). Daraus haben sich Mono- (27–30) und Di-enolacetate (34–39) darstellen lassen. Die letzteren sind Derivate des 1-Benzoxepins, 1-Benzothiepins und 1-Benzothiepin-1.1-dioxids.

Synthese von Derivaten des 1‐Benzoxepins, 1‐Benzothiepins und 1‐Benzothiepin‐1.1‐dioxids

Aus 3.5-Diacetoxy-4-phenyl-1-benzoxepin (1) entsteht beim Erhitzen in Xylol 2.4-Diacetoxy-3-phenyl-naphthol-(1) (6); mit Natriumacetat/Acetanhydrid erhalt man das entsprechende Acetat. Aus dem gleichartigen 1-Benzothiepin 2 bekommt man beim Erhitzen in Xylol und auch mit Pyridin/Acetanhydrid unter Eliminierung von Schwefel 1.3-Diacetoxy-2-phenylnaphthalin (5); mit Natriumacetat/Acetanhydrid entsteht dagegen der Thioessigsaure-S-[2.4-diacetoxy-3-phenyl-naphthyl-(1)-ester] (7). Das analoge 1-Benzothiepin-1.1-dioxid (9) liefert mit Natriumacetat/Acetanhydrid in einer andersartig verlaufenden Umlagerung das Cyclobuta[b]-1-benzothiophen-3.3-dioxid 10, dessen Struktur durch Abbau gesichert wird.

Helmut Westernacher

Papers

Synthese von Derivaten des 1‐Benzoxepins, 1‐Benzothiepins und 1‐Benzothiepin‐1.1‐dioxids

Umlagerungsreaktionen von Derivaten des 1‐Benzoxepins, 1‐Benzothiepins und des 1‐Benzothiepin‐1.1‐dioxids

Synthesis of Derivatives of Benzo[b]thiepin and Benzo[b]thiepin 1,1‐Dioxide

Synthese von Derivaten des Benzo[b]thiepins und Benzo[b]thiepin‐1, 1‐dioxids

Umlagerungen von Derivaten des Benzo[b]-thiepins und Benzo[b]thiepin-1,1-dioxids