Chiral cationic phosphonites: Applications towards the enantioselective synthesis of helicenes and related polyarenes

• Applicant: Professor Dr. Manuel Alcarazo
• Subject Area: Organic Molecular Chemistry - Synthesis and Characterisation
• Term: from 2011 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 209931430

• Final Report Year: 2021

Final Report Abstract

In conclusion, our work demonstrates that chiral cationic phosphonites derived from TADDOL and BINOL are excellent ancillary ligands for the Au-catalysed enantioselective assembly of [4]- and [5]helicenes, and the highly atroposelective synthesis of 1,1’-binaphthalene-2,3’-diols. The common step of all these processes is an intramolecular hydroarylation reaction, which takes place with high enantioselectivity by the use of our ligands. We anticipate that other hydroarylation processes, for example those leading to the synthesis of heterohelicenes or other chiral polyaromatic molecules might also benefit from the ligands already available. On the other hand, the employment of α-cationic phosphines beyond π-acid catalysis is still very limited. We have recently been able to dimerize norbornadiene into 2 3,13 4,11 5,9 10,14 heptacyclo[6.6.0.0 ,6.0 .0 .0 .0 ] tetradecane employing a Rh-complex that contains a dicationic phosphine ligand; however, more transformations need to be explored to verify whether they can benefit from the use of cationic ligands. We look forward to address these two topics in the near future.

Publications

• "Enantioselective Synthesis of 1,12‐Disubstituted [4]Helicenes." Angew. Chem. Int. Ed. 2020, 59, 5660-5664
  Hartung, Thierry; Machleid, Rafael; Simon, Martin; Golz, Christopher & Alcarazo, Manuel
  
• "Enantioselective Synthesis of 1‐Aryl Benzo[5]helicenes Using BINOL‐Derived Cationic Phosphonites as Ancillary Ligands." Angew. Chem. Int. Ed. 2020, 59, 23527-23531
  Redero, Pablo; Hartung, Thierry; Zhang, Jianwei; Nicholls, Leo D. M.; Zichen, Guo; Simon, Martin; Golz, Christopher & Alcarazo, Manuel
  
• "Gold‐Catalyzed Atroposelective Synthesis of 1,1′‐Binaphthalene‐2,3′‐diols." Angew. Chem. Int. Ed. 2020, 59, 5647-5650
  Zhang, Jianwei; Simon, Martin; Golz, Christopher & Alcarazo, Manuel
  
• "Synthesis of Cycloheptatrienes, Oxepines, Thiepines, and Silepines: A Comparison between Brønsted Acid and Au‐Catalysis." Eur. J. Org. Chem. 2020, 6245–6254
  Sprenger, Kristin; Golz, Christopher & Alcarazo, Manuel
  
• "In-Fjord Substitution in Expanded Helicenes: Effects of the Insert on the Inversion Barrier and Helical Pitch." Chem. Eur. J. 2021, 27, 13358-13366
  S. Suárez-Pantiga, P. Redero, X. Aniban, M. Simon, C. Golz, R. A. Mata, M. Alcarazo