2,5-dichloropentacyclo[4.3.0.02,5.03,8.04,7]non-3-ene: Generation and trapping of a homocubene and ab initio mo calculations on this and related molecules

✍ Scribed by Rosendorfer, Karin ;Jarosch, Oliver ;Polborn, Kurt ;Szeimies, Günter

• Publisher: John Wiley and Sons
• Year: 1995
• Tongue: English
• Weight: 800 KB
• Volume: 1995
• Category: Article
• ISSN: 0947-3440
• DOI: 10.1002/jlac.1995199510247

✦ Synopsis

Abstract

Reaction of bromotrichlorohomocubane 8 with MeLi in the presence of anthracene, 9,10‐dimethoxyanthracene, 1,2,3‐tri‐methylisoindole, diphenylisobenzofuran, and 2,5‐dimethyl‐furan furnished Diels‐Alder adducts of the title compound 2,5‐dichlorohomocubene 7 in reasonable yields. Adduct 14a was dechlorinated by reduction with Na in tert‐butyl alcohol to afford 14b. This compound could be selectively isomerized by AgBF~4~ to 20 and by the rhodium(I) complex 22 to a sensitive intermediate which could be reduced to 25. The structures of adduct 15a and of 14b were confirmed by X‐ray analysis, ensuring that bridgehead olefin 7 had been trapped. Ab initio MO calculations show that 7 is lower in energy than 11 and 12. The extension of the MO calculations to all parent homocubenes (2, 3, 26, 27, 28) and to dehydrohomocubanes 6 and 29 was carried out to obtain information on their relative energies, their structures, and their singlet‐triplet energy separation.