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Formation of 3‐Sulfonyl‐Substituted Benzo[ a ]heptalene‐2,4‐diols from Heptalene‐1,2‐dicarboxylates and Lithiomethyl Phenyl Sulfones
Author(s) -
Lutz Marc,
Linden Anthony,
AbouHadeed Khaled,
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(19990310)82:3<372::aid-hlca372>3.0.co;2-h
Subject(s) - chemistry , substituent , yield (engineering) , sulfone , medicinal chemistry , diol , stereochemistry , organic chemistry , materials science , metallurgy
On treatment with 6 mol‐equiv. of lithiomethyl phenyl sulfone at −78° in THF, dimethyl 5,6,8,10‐tetramethylheptalene‐1,2‐dicarboxylate ( 1′b ) gives, after raising the temperature to −10° and addition of 6 mol‐equiv. of BuLi, followed by further warming to ambient temperature, the corresponding 3‐(phenylsulfonyl)benzo[ a ]heptalene‐2,4‐diol 2b in yields up to 65% ( cf . Scheme 6 and Table 2 ), in contrast to its double‐bond‐shifted (DBS) isomer 1b which gave 2b in a yield of only 6% [1]. The bisanion [ 9 ] 2− of the cyclopenta[ a ]heptalen‐1(1 H )‐one 9 ( cf. Fig. 1 ), carrying a (phenylsulfonyl)methyl substituent at C(11b), seems to be a key intermediate on the reaction path to 2b , because 9 is transformed in high yield into 2b in the presence of 6 mol‐equiv. of BuLi in the temperature range of −10° to room temperature ( cf. Scheme 7 ). Heptalene‐dicarboxylate 1′b was also transformed into benzo[ a ]heptalene‐2,4‐diols 2c – g by a number of lithiated methyl X‐phenyl sulfones and BuLi ( cf. Scheme 9 and Table 3 ).