Photoredox chemistry in the synthesis of 2-aminoazoles implicated in prebiotic nucleic acid synthesis

Prebiotically plausible ferrocyanide–ferricyanide photoredox cycling oxidatively converts thiourea to cyanamide, whilst HCN is reductively homologated to intermediates which either react directly with the cyanamide giving 2-aminoazoles, or have the potential to do so upon loss of HCN from the system. Thiourea itself is produced by heating ammonium thiocyanate, a product of the reaction of HCN and hydrogen sulfide under UV irradiation.