2,2′-Biphenols via Protecting Group-Free Thermal or Microwave-Accelerated Suzuki–Miyaura Coupling in Water

User-friendly protocols for the protecting group-free synthesis of 2,2′-biphenols via Suzuki–Miyaura coupling of <i>o</i>-halophenols and <i>o</i>-boronophenol are presented. The reactions proceed in water in the presence of simple additives such as K₂CO₃, KOH, KF, or TBAF and with commercially available Pd/C as precatalyst. Expensive or laboriously synthesized ligands or other additives are not required. In the case of bromophenols, efficient rate acceleration and short reaction times were accomplished by microwave irradiation

Asymmetric Synthesis of Nonracemic 2‑Amino[6]helicenes and Their Self-Assembly into Langmuir Films

Alternative ways of preparing nonracemic 2-amino[6]­helicene derivatives were explored. The enantioselective [2 + 2 + 2] cycloisomerization of a nonchiral triyne under Ni­(cod)₂/(<i>R</i>)-QUINAP catalysis delivered the enantioenriched (+)-(<i>P</i>)-2-aminodibenzo­[6]­helicene derivative in 67% ee. An ultimate “point-to-helical” chirality transfer was observed in the cyclization of enantiopure triynes mediated by Ni­(CO)₂(PPh₃)₂ affording (−)-(<i>M</i>)- or (+)-(<i>P</i>)-7,8-bis­(<i>p</i>-tolyl)­hexahelicen-2-amine in >99% ee as well as its benzoderivative in >99% ee. The latter mode of stereocontrol was inefficient for a 2-aminobenzo[6]­helicene congener with an embedded five-membered ring. The <i>rac</i>-, (−)-(<i>M</i>)-, and (+)-(<i>P</i>)-7,8-bis­(<i>p</i>-tolyl)­hexahelicen-2-amines formed Langmuir monolayers at the air–water interface featuring practically identical surface pressure vs mean molecular area isotherms. The corresponding Langmuir–Blodgett films on quartz or silicon substrates were characterized by UV–vis/ECD spectroscopy and AFM microscopy, respectively