Synthese von neuen Heptalenderivaten

Abstract

Guaiazulene (9), in boiling 1,2,3,4-tetrahydronaphthalene, reacts with dimethyl acetylenedicarboxylate (ADM) to yield dimethyl-7-isopropyl-5,10-dimethylheptalene-1,2-dicarboxylate (10) as the main product and dimethyl-7-isopropyl-4-methylazulene-1,2-dicarboxylate (11) as a by-product (see scheme 2). A second heptalene derivative, occurring only in minor amounts in the reaction mixture, was found to be formed from 10 in a consecutive thermal reaction (scheme 2). Its structure, namely dimethyl-7-isopropyl- 5,10-dimethylheptalene-1,3-dicarboxylate (13), was established by spectroscopic means (for cyclic voltametry of the new compounds see figure and table). Both heptalene derivative 10 and 13, as well as the heptalene compound formed in the reaction of ADM with vetivazulene (see footnote 2), exhibit in ¹H- and ¹³ C-NMR-spectroscopy isopropyl moieties with diastereotopic methyl groups, i.e. the chiral heptalene structure does not invert according to the NMR time scale.