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Versuche zur Synthese von Nonafulvenen und von Nonaheptafulvalen
Author(s) -
Rutsch Werner,
Frey Alfred,
Neuenschawander Markus,
Engel Peter
Publication year - 1979
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19790620311
Subject(s) - chemistry , isomerization , bicyclic molecule , bromide , medicinal chemistry , valence (chemistry) , lithium (medication) , pyrolysis , stereochemistry , organic chemistry , catalysis , medicine , endocrinology
Attempted Synthesis of Nonafulvenes and of Nonaheptafulvalene The reaction of cyclononatetraenide with α‐bromobenzyl acetate ( 6 ) as well as with 1,1‐dihalodimethylether gives at −50°, instead of the expected cyclononatetraenes, bicyclo[6.1.0]nona‐2,4,6‐triene derivatives 10d and 16 ( Scheme 3 and 5 , respectively). It seems that in some cases the well known thermally disrotative valence isomerization of cyclononatetraenes 7 to 3a, 7a‐dihydroindenes 8 is much slower than the formation of bicyclo[6.1.0]nona‐2,4,6‐trienes of the type 10 and 16 . This type of reaction hurts the Woodward‐Hoffmann rules. Possible precursors of the attractive nonaheptafulvalene are prepared by reaction of acetoxy‐tropylium fluoborate ( 19a ) as well as of bromo‐tropylium bromide ( 19b ) with lithium‐cyclononatetraenide (Scheme 8) . So far, the attempted gas‐phase pyrolysis of the precursors 21a and 21b failed to give nonaheptafulvalene (5).