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.
Quinoxalines, also known as benzopyrazines, are heterocyclic compounds containing a ring complex consisting of a benzene ring and a pyrazine ring. It has isomerism with other naphthalene compounds such as quinazoline, phthalazine, cinnamine, etc. Fusion N-heterocyclic compounds are widely used as valuable entities for the expansion of important pharmacological agents and are considered to be an advantageous scaffold material. Among the numerous fused N-heterocyclic compounds, cinnoline, quinoxaline and quinazoline are important pharmacological agents. In medicinal chemistry, these N-heterocyclic compounds have a wide range of biological properties and can be used as synthetic intermediates, potential drug candidates and chemical probes.
Benzodioxanes are a class of isomeric compounds with the molecular formula C8H8O2. The three isomers of benzodioxane are 1,2-benzodioxane, 1,3-benzodioxane and 1,4-benzodioxane. 1,4-Benzodioxane has long been a versatile template widely used to design molecules with diverse biological activities. Its use spans past decades in medicinal chemistry to today, involving many drug discovery strategies, not excluding the most advanced ones. 1,4-Benzodioxane derivatives have been described as agonists and antagonists of nicotinic, alpha-adrenergic and 5-HT receptor subtypes. 1,4-Benzodioxane derivatives have been also reported as antitumor and antibacterial agents.