The reaction of 1-ethynyl-8-halonaphthalenes 1 with nitriles in the presence of the catalytic system [NiBr2(dppe)]/Zn (dppe=1,2-bis(diphenylphosphino)ethane) is found to produce unusual pyrroloarenes 2. The carbon-nitrogen triple bond in nitrile is activated twice, and five new bonds are formed in a one-pot transformation, which causes a pyrrole and two six-membered rings to be generated simultaneously. The scope and limitations of this reaction are examined. Similarly, alkyl-bridged diynes also furnish the corresponding polycycles. Diaryl-substituted cycloadducts 2 (R 1=Ar) are fluxional, because of the restriction in rotation of the aryl groups. The rotational barrier is studied by performing 1Ha NMR experiments at various temperatures. The structures of several compounds are determined by X-ray crystallographic analysis. The photophysical and electrochemical properties of the pyrroloarenes are also investigated. (Ni)triles and tribulations: The reaction of 1-ethynyl-8-halonaphthalenes 1 with nitriles in the presence of the catalytic system [NiBr2(dppe)]/Zn (dppe=1,2-bis(diphenylphosphino)ethane) produces unusual pyrroloarenes 2, which have unusual structures (see scheme) and exhibit interesting physical properties. The diluted solutions of these pyrroloarenes are strongly fluorescent, even under ambient light.
All Science Journal Classification (ASJC) codes
- Organic Chemistry