Chromene derivatives are an important class of compounds found in natural products and biologically active molecules. Some of the activities described in the literature include anticancer, antiprotozoal, antibacterial, antiviral and insecticidal. The most common members of this family are 4H-chromenes, 2H-chromenes, 2H-chromen-2-one (coumarins) and 4H-chromen-4-one (chromones), whose syntheses have been accomplished via many different routes. Other chalcogenochromenes, such as 4H-seleno- and 4H-tellurochromenes, are rather unusual, with only very few examples described in the literature. With these considerations in mind, we set out to design a useful and operationally simple route to 4H-chalcogenochromenes. The proposed methodology should be modular in order to accommodate a wide variety of functional groups, based on simple starting materials and at the same time allow the quick functionalization of the final product. We believed that a rapid cyclization process that at the same incorporated organochalcogenide substituents would meet these criteria as these groups are easily replaced by carbon-carbon, carbon-halogen and carbon-heteroatom bonds.These prerequisites led us to investigate iron(III)- promoted cyclization methodologies in which pendant alkynes are cyclized onto carbocyclic rings in the presence of dichalcogenides. In summary, we have described the synthesis of 4H-chalcogenochromene prepared via the iron(III)-promoted cyclization of organochalcogen propargylamines in the presence of diaryl dichalcogenides. Products with variations in the carbocyclic ring and at positions 2, 3 and 4 were obtained in moderate to excellent yields and a plausible mechanism based on HRMS experiments is proposed and discussed. In addition, we demonstrated the chemoselective C2-functionalization with four different electrophiles as well as the arylation of the same position with potassium aryl trifluoroborate salts via Suzuku- Miyaura reaction, adding nine more examples to the final scope.

Synthesis of substituted 4H-chalcogenochromenes promoted by iron(III) and diaryl dichalcogenides

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.