224768-52-9Relevant academic research and scientific papers
Formation of 3-sulfonyl-substituted benzo[a]heptalene-2,4-diols from heptalene-1,2-dicarboxylates and lithiomethyl phenyl sulfones
Lutz, Marc,Linden, Anthony,Abou-Hadeed, Khaled,Hansen, Hans-Juergen
, p. 372 - 388 (2007/10/03)
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 doublebond-shifted (DBS) isomer 1b which gave 2b in a yield of only 6% [1]. The bisanion [9]2- of the cyclopenta[a]heptalen-l(1H)-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). Heptalenedicarboxylate 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).
