672306-27-3Relevant academic research and scientific papers
A new alkylation method for heptalene-4,5-dicarboxylates their pseudoester forms
Abou-Hadeed, Khaled,Molnar, Zoltan A.,Goeksalit, Pinar,Kunz, Roland W.,Linden, Anthony,Hansen, Hans-Juergen
experimental part, p. 885 - 921 (2012/08/08)
Dimethyl heptalene-4,5-dicarboxylates3) undergo preferentially a Michael addition reaction at C(3) with α-lithiated alkyl phenyl sulfones at temperatures below -50°, leading to corresponding cis-configured 3,4-dihydroheptalene-4,5-dicarboxylates (cf. Table 1, Schemes 3 and 4). The corresponding heptalenofuran-1-one-type pseudoesters of dimethyl heptalene-4,5-dicarboxylates (Scheme 5) react with [(phenylsulfonyl)methyl] lithium almost exclusively at C(1) of the furanone group (Scheme 6). In contrast to this expected behavior, the uptake of 1-[phenylsulfonyl)ethyl]lithium occurs at C(5) of the heptalenofuran-1-ones as long as they carry a Me group at C(11) (Schemes 6 and 7). The 1,4- as well as the 1,6-addition products eliminate, on treatment with MeONa/MeOH in THF, benzenesulfinate, thus leading to 3- and 4-alkylated dimethyl heptalene-4,5-dicarboxylates, respectively (Schemes 8-13). The configuration of the addition reaction of the nucleophiles to the inherently chiral heptalenes is discussed in detail (cf. Schemes 14-19) on the basis of a number of X-ray crystal-structure determinations as well as by studies of the temperature-dependence of the 1H-NMR spectra of the addition products.
On the Formation of 2-Sulfonylbenzo[a]heptalene-1,3-diols as Precursors for the Synthesis of Colchicinoids
Abou-Hadeed, Khaled,Hansen, Hans-Juergen
, p. 4018 - 4047 (2007/10/03)
The benzo[a]heptalene formation from 4-[(R-sulfonyl)acetyl]heptalene-5-carboxylates 15 and 5-[(R-sulfonyl)acetyl]heptalene-4-carboxylates 16 (R = Ph or morpholino) in the presence of R′SO2CH2Li and BuLi has been investigated (Scheme 6). Only the sulfonyl moiety linked to the C=O group at C(4) of the heptalene skeleton is found at C(3) of the formed benzo[a]heptalene-2,4-diols 3 in accordance with the general mechanism of their formation (Scheme 3). Intermediates that might rearrange to corresponding 2-sulfonylbenzo[a]heptalene-1,3-diols lose HO-under the reaction conditions to yield the corresponding cyclopenta[d]heptalenones of type 11 (Schemes 6 and 7). However, the presence of an additional Me group at C(a) of the lithioalkyl sulfones suppresses the loss of HO-, and 4-methyl-2-sulfonylbenzo[a]heptalene-1,3-diols of type 4c have been isolated and characterized for the first time (Schemes 8 and 10). A number of X-ray crystal-structure analyses of starting materials and of the new benzo[a]heptalenes have been performed. Finally, benzo[a]heptalene 4c has been transformed into its 1,2,3-trimethoxy derivative 23, a benzo[a]heptalene with the colchicinoid substitution pattern at ring A (Scheme 11).
