Choline Hydroxide as an Efficient Catalyst for the Diastereoselective Synthesis of Trans-2,3-dihydrofuro[3,2-c]Coumarins in an Aqueous Medium

One-Pot Synthesis of 4H-Pyrano[3,2-c]coumarin Derivatives Catalyzed by Deep Eutectic Solvent

4H-Pyrano[3,2-c]coumarin derivatives are an important class of pharmaceutical compounds that are expensive to prepare by previously reported methods. An efficient and green method was developed to obtain these derivatives using the deep eutectic solvent (DES) zinc chloride/acetamide (n:n = 1:4), which acted as both the catalyst and the solvent for the reaction. An aromatic aldehyde, 4-hydroxycoumarin, and cyanoacetate were used as the substrates. The DES, substrate molar ratio, diluent type, temperature, and reaction time were optimized to obtain the 4H-pyrano[3,2-c]coumarin derivatives from a range of aromatic aldehydes in a single step in moderate to high yields and under mild reaction conditions.

The molecular diversity scope of 4-hydroxycoumarin in the synthesis of heterocyclic compounds via multicomponent reactions

4-Hydroxycoumarins are some of the most versatile heterocyclic scaffolds and are frequently applied in the synthesis of various organic compounds. 4-Hydroxycoumarin-based compounds are important among heterocyclic structures due to their biological and pharmaceutical activities. In this study, we provide an overview on the recent applications of 4-hydroxycoumarin in multicomponent reactions for the synthesis of various heterocyclic compounds during the time period of 2015-2018.

Green synthesis of trans-(4-chlorophenyl)-7-aryl-6,7-dihydro[1,3]dioxolo[4,5-f][1]benzofuran-6-yl)methanones in an aqueous medium

A three-component one-pot condensation of 2-[2-(4-chlorophenyl)-2-oxoethyl)]isoquinolinium bromide with benzo[1,3]dioxol-5-ol and an arylglyoxal in the presence of catalytic amounts of 1,4-diaza-bicyclo[2.2.2]octane in refluxing water gave a series of seven trans-(4-chlorophenyl)-7-aryl-6,7-dihydro[1,3]dioxolo[4,5- f][1]benzofuran-6-yl)methanones in excellent yield and in a short time.

Synthesis of a series of novel 2,3-dihydrofuranonaphthoquinone derivatives

A green and highly efficient synthesis of 12 novel trans-2-(4-chlorobenzoyl)-3-aryl-2,3-dihydronaphtho[2,3- b]furan-4,9-diones has been achieved via a three-component, one-pot condensation of 2-[2-(4-chlorophenyl)-2-oxoethyl)]isoquinolinium bromide with 2-hydroxy-1,4-naphthoquinone and an aromatic aldehyde in the presence of catalytic amounts of choline hydroxide in water under reflux conditions. The advantages of this method are a short reaction time, high yields and the avoidance of any hazardous organic solvent. Therefore, this procedure can be classified as green chemistry.

A clean, simple and efficient synthesis of trans-[3-(aryl)-2,3-dihydrofuro[3,2-h] quinolin-2-yl]-(4-chlorophenyl)methanones

We report a green and efficient method for the synthesis of trans-[3-(aryl)-2,3-dihydrofuro[3,2- h]quinolin-2-yl]-(4-chlorophenyl) methanones from the condensation of 2-[2-(4-chlorophenyl)-2-oxoethyl)]isoquinolinium bromide with 8-hydroxyquinoline and an aromatic aldehyde in the presence of catalytic amounts of choline hydroxide in water at reflux conditions. This new protocol employing choline hydroxide, which is a green and inexpensive catalyst, offers advantages such as mild reaction conditions, short reaction time, high yields and does not involve any hazardous solvent. Therefore, this procedure can be classified as green chemistry.

Green synthesis of trans-2-(4-chlorobenzoyl)-5-hydroxy-3-(aryl)-2,3-dihydrobenzofuran-4,7-diones

A green and efficient synthesis of trans-2-(4-chlorobenzoyl)-5-hydroxy-3-(aryl)-2,3-dihydrobenzofuran-4,7-diones has been achieved in excellent yield via a three-component one-pot condensation of 2-[2-(4-chlorophenyl)-2-oxoethyl)]isoquinolinium bromide with 2,5-dihydroxy-1,4-benzoquinone and aromatic aldehydes in the presence of catalytic amounts of choline hydroxide in water under reflux conditions. The salient features of this protocol are the short reaction time, the high yields and it does not involve any hazardous organic solvent.

Synthesis of Trans-6-(4-Chlorobenzoyl)-7-(Aryl)-1,3-Dimethyl-6,7-Dihydrofuro[3,2-d]Pyrimidine-2,4-Diones Using Choline Hydroxide as an Efficient Catalyst in an Aqueous Medium

A green and efficient synthesis of the trans-6-(4-chlorobenzoyl)-7-(aryl)-1,3-dimethyl-6,7-dihydrofuro[3,2-d]pyrimidine-2,4-diones has been achieved via a three-component, one-pot condensation of 2-[2-(4-chlorophenyl)-2-oxoethyl)]isoquinolinium bromide with 1,3-dimethylbarbituric acid and an aromatic aldehyde in the presence of catalytic amounts of choline hydroxide in water under reflux conditions. This gives trans-6-(4-chlorobenzoyl)-7-(aryl)-1,3-dimethyl-6,7-dihydrofuro[3,2-d]pyrimidine-2,4-diones in excellent yield and in short reaction times.

DABCO as an Efficient Catalyst for the Diastereoselective Synthesis of trans-(4-chlorophenyl)-7-aryl-6,7-dihydro-[1,3]dioxolo[4,5-f]benzofuran-6-yl) Methanone in an Aqueous Medium

A three-component one-pot condensation of 2-[2-(4-chlorophenyl)-2-oxoethyl)]isoquinolinium bromide with benzo[1,3]dioxol-5-ol and an aromatic aldehyde in the presence of catalytic amounts of 1,4-diaza-bicyclo[2.2.2]octane (DABCO) in refluxing water gives trans-(4-chlorophenyl)-7-aryl-6,7-dihydro-[1,3]dioxolo[4,5- f]benzofuran-6-yl)methanone in excellent yield and in short time.