Synthesis of Benzo[a]heptalenes via Benzanellation–Aromatization Sequence

✍ Scribed by Ekaterina A. Ochertyanova; Hans-Jürgen Hansen

• Publisher: John Wiley and Sons
• Year: 2002
• Tongue: German
• Weight: 148 KB
• Volume: 85
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/1522-2675(200204)85:4<1128::aid-hlca1128>3.0.co;2-q

✦ Synopsis

A novel approach towards the synthesis of functionalized benzo[a]heptalenes 9 and 10 via a 6pelectrocyclic ring closure ± aromatization sequence of corresponding bis[prop-2-enoates] 5 and 6 has been developed (Scheme 1). The starting bis[prop-2-enoates] have been prepared from the corresponding dialdehydes 3a and 4a in a Wittig-Horner reaction, and their UV/VIS properties have also been investigated (Fig. 1 and Table 1). The dehydrogenations of the corresponding diols 1 and 2 to dialdehydes with a number of oxidizing reagents, including MnO 2 in CH 2 Cl 2 , tetrapropylammonium perruthenate (TPAP), and activated DMSO, have been studied in detail.