Sulfur-assisted interconversion between N-confused porphyrin and N-fused porphyrin

The ring-opening reaction of N-fused tetraphenylporphyrin (NFTPP-H, 2) to C3-substituted N-confused tetraphenylporphyrin (NCTPP-S-Ar, 4) proceeded efficiently in 85–95% yields. Furthermore, removal of the C3-arylthio-substituents in 4 was achieved by the two types of desulfurization reactions. The Ni2B-mediated desulfurization afforded C3-free N-confused tetraphenylporphyrin (NCTPP-H, 1) whereas the radical-mediated desulfurization with (n-Bu)3Sn-H and AIBN promoted the ring-fusion to afford 2.