Preparation of New Nitrogen-Bridged Heterocycles 72. A New Approach to 1-Acyl-3-(substituted methylthio)thieno[3',4':4,5]imidazo[1,5-a]pyridine Derivatives

Abstract

Imidazo[1,2-a]pyridine derivatives have been synthesized by several methods and shown to have a variety of pharmacological actions such as antibacterial, antifungal, antiviral, antiinflammatory, hypnotic, and antiulcer activities. [2][3][4][5][6][7][8][9][10][11][12] In contrast, imidazo[1,2-a]pyridine derivatives fused with a hetero ring at the 2-and 3-positions have been scarcely reported because of the absence of a suitable preparative method for them. We have recently described the syntheses of 3-alkylthio-1-arylcarbonyl-6,8-dimethylthieno[3Ј,4Ј:4,5]imidazo[1,2-a]pyridines 13) and 3-acyl-4-methylthio-2H-pyrano [2Ј,3Ј:4,5]imidazo[1,2-a]pyridine-2-ones.14) The former compounds were unexpectedly obtained together with 2-alkylthio-1-arylcarbonylthio-6,8-dimethylindolizine-3-carbonitriles in the alkaline treatment of 1-[1-cyano-2-(phenacylthio)vinyl]-3,5-dimethylpyridinium bromides. The plausible reaction mechanisms ( Results and DiscussionPreparation of 3-Amino-4-(1-pyridinio)thiophene-5-thiolate Derivatives We thought that the S-alkylations of 3-amino-4-(1-pyridinio)thiophene-5-thiolates with various alkylating agents should smoothly lead to the key intermediates such as D described above. Hence, the syntheses of pyridinium betaines 4a-p were investigated according to Tominaga's method. 15) However, the reactions of 1-(cyanomethyl)pyridinium chlorides (1a-c), carbon disulfide, and phenacyl bromides (2a-c) or chloroacetone (2d) in the presence of a base always afforded the mixtures of the

Visible light mediated synthesis of 1,3-diarylated imidazo[1,5-a]pyridines via oxidative amination of C–H catalyzed by graphitic carbon nitride

“…27 Imidazo[1,5-a]pyridines are found in various natural products and synthetic compounds that are valuable in pharmaceutical and material chemistry. 28,29 However, there are only a limited number of synthetic pathways that utilize conventional Vilsmeier-type cyclization, while alternative methods have been developed. 30,31 Therefore, there is a strong need for uncovering a simpler approach to prepare imidazo[1,5-a]pyridines deploying readily accessible starting materials.…”

FeCl3-Catalyzed Synthesis of 6-Thioxo-hexahydroindeno[1′,2′:4,5]imidazo[1,5-a]pyridin-12(6H)-ones via an Interesting [1,2] Oxygen Shift Pathway

“…Imidazo­[1,5- a ]­pyridine derivatives with a nodal nitrogen atom are an important fused heterocyclic system that exhibit a wide range of medicinal activities including thromboxane A2 synthesis inhibitions, HIV-protease inhibitions, topoisomerase II inhibitions, DNA synthesis inhibitions, cytotoxic immunosuppression, and so forth. They are found in the core structure of various natural alkaloids and several drug-relevant molecules , like cribrostatin 6 . Also, they have shown applications in broad areas of research such as organic thin-layer field effect transistors (FET), photoluminescent sensors, and light-emitting diodes (OLEDs) .…”

Synthesis of 1,3-Disubstituted Imidazo[1,5-a]pyridines from Amino Acids via Catalytic Decarboxylative Intramolecular Cyclization

“…Imidazo­[1,5- a ]­pyridine scaffolds are present in various drug-relevant molecules and biologically active agents . Thus, method development for accessing this important structural motif is of high interest.…”