Microwave‐Enhanced Efficient Regioselective Synthesis of 1,3,4‐Trisubstituted 2‐Mercaptoimidazoles on a Soluble Support

Synthesis of Aminofuran-Linked Benzimidazoles and Cyanopyrrole-Fused Benzimidazoles by Condition-Based Skeletal Divergence

A condition-based skeletal divergent synthesis was explored to achieve skeletal diversity in two component condensation reaction. Cyanomethyl benzimidazole was reacted with α-bromoketone under thermal conditions to furnish 2-aminofuranyl-benzimidazoles, while the same reaction afforded 3-cyano-benzopyrrolo-imidazoles under microwave irradiation. Two nonequivalent nucleophilic centers on benzimidazole moiety were manipulated elegantly by different reaction conditions to achieve the skeletal diversity.

Synthesis of functionalized imidazolidine-2-thiones via NHC/base-promoted aza-benzoin/aza-acetalization domino reactions

Benzylidene thioureas were generated in situ from α-sulfonylamines and used as novel umpolung acceptors in aza-benzoin/aza-acetalization domino reactions giving 5-hydroxy-imidazolidine-2-thiones.

Microwave Controlled Reductive Cyclization: A Selective Synthesis of Novel Benzimidazole-alkyloxypyrrolo[1,2-a]quinoxalinones

An efficient cascade synthesis of novel benzimidazole linked alkyloxypyrrolo[1,2-a]quinoxalinones was explored on soluble polymer support under microwave irradiation. Two exclusive protocols have been developed for the partial and full reductive cyclization by controlling the microwave energy. Commencing from the same substrate, ortho nitro pyrrol carboxylates, N-hydroxy pyrroloquinoxalinones were obtained by partial reductive cyclization (60 °C, 7 min), and the synthesis of pyrroloquinoxalinones was accomplished by full reductive cyclization (85 °C, 12 min). This method represents the first synthesis of N-hydroxy pyrroloquinoxalinones using Pd/C and ammonium formate as reducing agents. Further employing a variety of alkyl bromides, the obtained pyrroloquinoxalinones were transformed to their corresponding O- and N-alkylated analogues to deliver the diversified, novel molecular entities.

Unprecedented one-pot chemocontrolled entry to thioxoimidazolidinones and aminoimidazolones: synthesis of kinase inhibitor leucettamine B

A novel and highly chemoselective protocol for the construction of thioxoimidazolidinone and aminoimidazolone frameworks was explored, and the influence of the reaction conditions on product formation was studied to establish two distinct approaches for their selective formation. In this one-pot reaction, ambient temperature generally resulted in the formation of thioxoimidazolidinones, whereas microwave irradiation provided aminoimidazolones exclusively. An attempt to elucidate the observed chemoselectivity is described, and the products were confirmed by X-ray studies. One-pot synthesis toward Leucettamine B, a marine alkaloid, was achieved on the basis of this protocol.