56594-78-6Relevant academic research and scientific papers
Thermal Reaction of Highly Alkylated Azulenes with Dimethyl Acetylenedicarboxylate: HOMO(Azulene) vs. SHOMO(Azulene) Control in the Primary Thermal Addition Step
Chen, Yi,Kunz, Roland W.,Uebelhart, Peter,Weber, Roland H.,Hansen, Hans-Juergen
, p. 2447 - 2492 (1992)
The reaction of highly alkylated azulenes with dimethyl acetylenedicarboxylate (ADM) in decalin or tetralin at 180-200 deg C yields, beside the expected heptalene- and azulene-1,2-dicarboxylates, tetracyclic compounds of type "anti"-V and tricyclic compounds of type E (cf.Schemes 2-4 and 8-11).The compounds of type "anti"-V represent Diels-Alder adducts of the primary tricyclic intermediates A with ADM.In some cases, the tricyclic compounds of type E also underwent a consecutive Diels-Alder reaction with ADM to yield the tetracyclic compounds of type "anti"- or "syn"-VI (cf.Schemes 2 and 8-11).The tricyclic compounds of type E, namely 4 and 8, reversibly rearrange via -C shifts to isomeric tricyclic structures (cf. 18 and 19, respectively, in Scheme 6) already at temperatures > 50 deg C.Photochemically 4 rearranges to a corresponding tetracyclic compound 20 via a di-?-methane reaction.The observed heptalene- and azulene-1,2-dicarboxylates as well as the tetracyclic compounds of type "anti"-V are formed from the primary tricyclic intermediate A via rearrangement (-> heptalenedicarboxylates), retro-Diels-Alder reaction (-> azulenedicarboxylates), and Diels-Alder reaction with ADM.The different reaction channels of A are dependent on the substituents.However, the main reaction channel of A is its retro-Diels-Alder reaction to the starting materials (azulene and ADM).The highly reversible Diels-Alder reaction of ADM to the five-membered ring of the azulenes is HOMO(azulene)/LUMO(ADM)-controlled, in contrast to that at 200 deg C irreversible ADM addition to the seven-membered ring of the azulenes to yield the Diels-Alder products of type E.This competing reaction must occur on grounds of orbital-symmetry conservation under SHOMO(azulene)/LUMO(ADM) control (cf.Schemes 20-22).Several X-ray diffraction analysis of the products were performed (cf.Chapt. 4.1).
Synthesis and properties of syn-[2.2](l,6)- and (4,6)Azulenophanes and macrocyclic azulenophanes
Chen, Shu-Ling,Klein, Roland,Hafner, Klaus
, p. 423 - 433 (2007/10/03)
A regioselective synthesis of syn-[2.2](1,6)azulenophane (9) and syn-[2.2](4,6)azulenophane (12) is described. Azulenophane 9 is prepared by deprotonation of 1,2-bis(6-methylazulen-1-yl)ethane (5), followed by oxidative coupling of the initially formed dilithium salt 8 with iodine under highdilution conditions in 17 % yield, along with the macrocyclic [2.2.2.2](1,6)azulenophane (10) (3%), and [2.2.2.2.2.2] (1,6)azulenophane (11) (1.5%). The azulenophane 12 and the macrocyclic [2.2.2.2](4,6)azulenophane (13) are obtained by coupling of the dianion of 1,2-bis(4-methylazulen-6-yl)ethane (14). The structural assignments of the title compounds are based on their spectral data. Protonation of 9 furnishes the mono- and dications 24 and 25, respectively, of which the first exhibits a charge-transfer band in its electronic spectrum, indicating a transannular interaction between the protonated and unprotonated azulene units. Protonation of 12 yields the mono- and dications 26 and 27, respectively. In contrast to 24, no new band due to an intramolecular transannular charge-transfer interaction is observed in the electronic spectrum of 26, and this is due to an insufficient overlap between the protonated and unprotonated azulene decks in 26. Vilsmeier formylation of 9 with 1.5 mol equivalents of phosphoryl chloride in DMF at room temp, yields 3-formyl-syn-[2.2](1,6)azulenophane (28) in 15% yield. Under the same reaction conditions a double formylation of 9 with 3 mol equivalents of phosphoryl chloride leads to 3,3′-diformyl-syn-[2.2](1.6)azulenophane (29) in 42% yield. The aminomethylation of 9 with paraformaldehyde and N,N,N′ ,N′ -tetramethyldiaminoniethane in the presence of acetic acid furnishes the Mannich bases 3-N,N-dimethylaminomethyl-syn-[2.2](1,6)azulenophane (30) and 3,3′ -bis(N,N-dimethylaminomethyl)-syn-[2.2](1,6)azulenophane (31) in 40% and 46% yields, respectively.
