A Lewis Base Hydrogen Bond Donor (LB/HBD) Organocatalytic Approach to Dithiabridged Triarylamine Hetero[4]helicenes

N-thiophthalimido- arylphenothiazines 2 and triarylamines 3 can be converted to dithiabridged triarylamine hetero[4]helicenes 1 using catalytic amounts of chalcogen substituted Lewis Bases and hexafluoro isopropanol as hydrogen bond donor. The procedure occurs under mild reaction conditions and gives good yields avoiding the use of excesses of Lewis Acids as previously reported. A preliminary study about the possibility to control the M and P absolute stereochemistry of helicenes 1 using enantiopure sulfur containing LBs from the natural chiral pool is also reported.

Automated summary

This article reports the conversion of N-thiophthalimido-arylphenothiazines 2 and triarylamines 3 to dithiabridged triarylamine hetero[4]helicenes 1 using catalytic amounts of chalcogen substituted Lewis Bases and hexafluoro isopropanol as hydrogen bond donor. The procedure provides good yields under mild reaction conditions without the need for excess Lewis Acids. It also presents a preliminary study on the control of the M and P absolute stereochemistry of helicenes 1 using enantiopure sulfur containing Lewis Bases from the natural chiral pool.