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

Abstract

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.