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Highly Functionalized Tris‐(σ)π‐Homobenzenes — Nine‐Membered Ring Compounds with Special Substitution Patterns — En Route to cis,cis,cis ‐2,5,8‐Cyclononatriene‐1,4,7‐trione
Author(s) -
Person Georg,
Keller Manfred,
Prinzbach Horst
Publication year - 1996
Publication title -
liebigs annalen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0947-3440
DOI - 10.1002/jlac.199619960410
Subject(s) - hexa , chemistry , tris , epoxide , ring (chemistry) , stereochemistry , sequence (biology) , derivative (finance) , combinatorial chemistry , medicinal chemistry , organic chemistry , catalysis , biochemistry , financial economics , economics
In the pursuit of the tris‐(σ)π‐homobenzene chemistry, the synthesis of potentially tri(hexa)podal, C 3 v ‐symmetrical, polyfunctionalized 9‐membered ring systems is being explored. A rather “expensive” tris‐σ‐homobenzene ( 13b ) is the starting material for the tris‐σ‐isomer ( 14b ) from which 1,4,7‐trimethylene‐cyclononatriene ( 2 ), its tri(hexa)epoxides ( 18 , 20 ) and triepoxytriketo derivative ( 19 ) are prepared through generally highly selective transformations. An alternative approach toward the C 3 v 2,5,8‐cyclononatriene‐1,4,7‐trione [ 4 , C 6 H 6 (CO) 3 ] starts from the relatively “cheap” all‐ exo ‐1,4,7‐cyclononatriene‐trioxide ( 32 ), relies on selective epoxide opening reactions, and is complicated by typical mediumring transanular cyclizations; the rather efficient six‐step sequence does not reach the stated goal but carries attractive preparative prospects. For a central intermediate in each approach (trimethylenetrioxide 18 and bromo‐hydroxy‐diepoxycyclononane 50 ), X‐ray structural data are presented.