Synthetic Uses of Thiophen Derivatives

Synthetic Uses of Thiophen Derivatives.—The reaction between dimethyl diazo-malonate and thiophen is catalysed by rhodium salts the product is a stable ylide (36) which can be used as an equivalent of bis(methoxycarbonyl)carbene. Thus the heating of (36) with cyclo-octene under reflux affords the bicyclononane (37) in 

Reagents i, Rhodium salts ii, cyclo-octene, heat 

Naphthothiophens, especiaUy Thiapseudophenalenones.—Neidlein (see Vol. 5, p. 291) has continued his interesting work on these remarkable thiophen analogues of phenalene and phenalenium cations a series of papers describes the synthesis and properties of compounds such as (38).  

Thiophen Rings Fused to other Heteroaromatic Systems that do not contain Sulphur, Selenium, or Tellurium.—Very many such annelated systems have been described, and in this section only those of particular note are mentioned. Annelation to other sulphur-, selenium-, and tellurium-containing rings is considered in a later section (p. 296). 

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