[3]Dendralene (2) has been converted into the benz[a]anthracene tetraester 13 in a protocol involving diene-transmissive Diels-Alder addition of dimethyl acetylenedicarboxylate to 2 followed by a sequence of reduction-addition-aromatization

SummaryFirst attempts are described to prepare a precursor for an all-carbon analog of indigo, the tetracyclic triene 4. Starting from indan-2-one (9) the α-methylene ketone 13 was prepared. Upon subjecting this compound to a McMurry coupling reaction, it dimerized to the bis-indene derivative 17, rather than providing the tetramethyl derivative of 4, the hydrocarbon 14. In a second approach, indan-1-one (18) was dimerized to the conjugated enedione 21 through the bis-1-indene dimer 19. All attempts to methylenate 21 failed, however. When 19 was treated with the Tebbe reagent, the dimer 23 was produced, presumably through a Cope reaction of the intermediately generated isomer 22. The bis-indene derivative 23 can be alkylated with 1,2-dibromoethane to produce a 1:1 mixture of the spiro compounds 24 and 25. Although 9 could be reductively dimerized to 30, the conversion of this olefin to 14 failed.

Novel Dienes and Dienophiles. Part 8. Highly Functionalized, Angularly Anellated Aromatic Compounds from Dendralenes. -Cross-conjugated oligoenes [3]dendralene (I) or [4]dendralene (XI) undergo diene-transmissive Diels-Alder reactions with acetylenedicarboxylate (II) to give cycloadducts which are further elaborated to afford the desired polycycles (X) and (XIV). -(HOPF*, H.; YILDIZHAN, S.; Eur.

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