**3. Synthesis of oxygen-containing heterocycles**

### **3.1 Furans**

Furan moieties are important substructures that have been found in numerous natural products, such as kailolides and combranolides. These heterocycles are

*Synthesis of Five-Membered Heterocycles Using Water as a Solvent DOI: http://dx.doi.org/10.5772/intechopen.108929*

**Figure 11.**

*Synthesis of 5-(furan-3-yl)barbiturate/thiobarbiturate derivatives.*

#### **Figure 12.**

*Synthesis of 2-(cyclohexylamino)-3-aryl-indeno [1,2-b] furan-4-ones in water.*

also found in a variety of commercial products such as pharmaceuticals, fragrances and dyes.

A simple three-component reaction between arylglyoxal monohydrates, acetylacetone and barbituric or thiobarbituric acid resulted in the synthesis of polyfunctionalized 5-(furan-3- yl)barbiturates and 5-(furan-3-yl)thiobarbiturate derivatives in good yields (**Figure 11**). The method employs readily available starting materials, neutral reaction conditions and water as an environmentally green solvent [19].

An efficient and a simple synthesis of 2-(cyclohexylamino)-3-aryl- indeno[1,2-b] furan-4-ones was attained via a one-pot three-component reaction of aldehydes, cyclohexylisocyanide and 1,3-indandione in water for 5 h in excellent yields (**Figure 12**). Water was used as a solvent to avoid the use of other highly toxic and environmentally unfavourable solvents for this synthesis [20].
