Thiophene is a five-membered heterocyclic compound containing a sulfur heteroatom with the molecular formula C4H4S. Thiophene is aromatic and is very similar to benzene; electrophilic substitution reaction is easier than benzene, and it is mainly substituted at the 2-position. Thiophene ring system has certain stability to oxidant.
Pyrans are an important class of six-membered heterocyclic compounds, non-aromatic rings, composed of five carbon atoms and one oxygen atom, and contain two double bonds. The molecular formula of pyran is C5H6O, and there are two isomers. Pyrans, together with benzo derivatives, form scaffolds for a variety of drug applications, many of which are approved and promising candidates in clinical trials and recently isolated bioactive natural products.
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