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New Syntheses of Di‐ π ‐Substituted Heptalenes
Author(s) -
Song Jianfeng,
Hansen HansJürgen
Publication year - 1999
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/(sici)1522-2675(19991215)82:12<2260::aid-hlca2260>3.0.co;2-z
Subject(s) - chemistry , substituent , benzaldehyde , medicinal chemistry , double bond , reaction conditions , wittig reaction , stereochemistry , organic chemistry , catalysis
To study the effect of double‐bond shifts (DBS) in different type of heptalenes linked to extended π ‐systems, several di‐ π ‐substituted heptalenes were synthesized. 6‐[( E )‐Styryl]heptalene‐dicarboxylate 4 was smoothly converted to 1‐(chloromethyl)heptalene‐dicarboxylate 5 by treatment with t ‐BuOK and C 2 Cl 6 in THF at −78°. The one‐pot reaction of 5 and P(OEt) 3 in the presence of NaI, followed by Wittig‐Horner reaction, afforded the 1,6‐di‐ π ‐substituted heptalene 6 . The reaction of 6‐[(1 E ,3 E )‐4‐phenylbuta‐1,3‐dienyl]heptalenes 7 or 15 with t ‐BuOK and benzaldehyde in THF led to the formation of the 1,6‐di‐ π ‐substituted heptalenes 13 or 16 , together with transesterification products 14 or 17 . The transformation of the MeOCO group at C(4) of 6‐[( E )‐styryl]heptalene‐dicarboxylate 4 to a phenylbuta‐1,3‐dienyl substituent afforded the 4,6‐di‐ π ‐substituted heptalene 21a , which is in thermal equilibrium with its DBS isomer 21b in solution. Oxidation of heptalene 22 with SeO 2 in dioxane gave carbaldehyde 23 , which was then subjected to a Wittig reaction to give the 6,9‐di‐ π ‐substituted heptalene‐dicarboxylate 24 .