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Synthesis of 6‐Styrylheptalenes
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(19991006)82:10<1690::aid-hlca1690>3.0.co;2-d
Subject(s) - chemistry , formylation , wittig reaction , phosphonium , azulene , aqueous solution , hydrolysis , dimethyl acetylenedicarboxylate , tetrahydrofuran , medicinal chemistry , toluene , yield (engineering) , organic chemistry , catalysis , materials science , solvent , cycloaddition , metallurgy
4‐Methylazulenes 3 , 15 , and 23 were transformed into 4‐[(methylthio)methyl]azulene 4 , and azulene‐4‐carbaldehyde dimethyl dithioacetals 16 and 24 , respectively. Vilsmeier formylation of 4 and 16 , and subsequent reduction led to the 1‐methyl derivatives 6 and 18 , respectively. The thermal reaction of azulenes 6 , 18 , and 24 with dimethyl acetylenedicarboxylate (ADM) in toluene afforded heptalenes with a (methylthio)methyl group or a [bis(methylthio)]methyl group at C(6). Chlorination of [(methylthio)methyl]heptalene 7 , followed by treatment with HgO and BF 3 ⋅OEt 2 in aqueous tetrahydrofuran (THF), led to 6‐formylheptalene‐dicarboxylate 12 in excellent yield. Similarly, hydrolysis of 18 and 24 by HgO and BF 3 ⋅OEt 2 in aqueous THF afforded the 6‐formyl derivatives 21 and 27 , respectively. Wittig reaction of the 6‐formyl‐substituted heptalenes and phosphonium salts 13a – e in the two‐phase system CH 2 Cl 2 /2 n aqueous NaOH resulted in the formation of 6‐styryl‐substituted heptalenes.