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Carbon–carbon bond formation is one of the most important tools in synthetic organic chemists’ toolbox. It is a fundamental transformation that allows synthetic chemists to synthesize the carbon framework of complex molecules from inexpensive simple starting materials. Among the many synthetic methodologies developed for the construction of carbon–carbon bonds, organocopper reagents are one of the most reliable organometallic reagents for this purpose. The versatility of organocuprate reagents or the reactions catalyzed by organocopper reagents were demonstrated by their applications in a variety of synthetic transformations including the 1,4-conjugate addition reactions. Sulfur-containing heterocyclic compounds are a much less studied area compared to oxygen-containing heterocycles but have gained more and more attention in recent years due to their rich biological activities and widespread applications in pharmaceuticals, agrochemicals, and material science. This paper will provide a brief review on recent progress on the synthesis of an important class of sulfur-heterocycles-2-alkylthiochroman-4-ones and thioflavanones via the conjugate additions of Grignard reagents to thiochromones catalyzed by copper catalysts. Recent progress on the synthesis of 2-substituted thiochroman-4-ones via alkynylation and alkenylation of thiochromones will also be covered in this review. 

Undergraduate research is well recognized as an effective high-impact educational practice associated with student success in higher education. Actively engaging students in research experiences is considered as one of the several high-impact practices by many agencies including the American Chemical Society. Developing and maintaining an active undergraduate research program benefits both the faculty and students especially those from under-represented minority groups (URM). The infusion of research experiences into undergraduate curriculum enables students from all backgrounds to develop independent critical thinking skills, written and oral communications skills that are very important for successful careers in “STEM” area. Several strategies and activities such as a Peer Mentoring Program (PMP), funded research activities, the infusion of research into organic chemistry labs, undergraduate professional development, research group meetings, presentations at regional/national conferences, and publishing as co-authors on peer-review papers are vital in creating a welcoming research group that promotes the diversity, equity, and inclusion in organic chemistry education. The experiences working on funded research projects, presenting their research data at conferences and publishing papers as co-authors will greatly increase the under-represented minority (URM) students’ chance in landing a job or getting admitted into graduate/professional programs in STEM area. 

Grignard reagents undergo conjugate addition to thiochromones catalyzed by copper salts to afford 2-substituted-thiochroman-4-ones, both 2-alkylthiochroman-4-ones and thioflavanones (2-arylthiochroman-4-ones), in good yields with trimethylsilyl chloride (TMSCl) as an additive. The best yields of 1,4-adducts can be attained with CuCN∙2LiCl as the copper source. Excellent yields of 2-alkyl-substituted thiochroman-4-ones and thioflavanones (2-aryl substituted) are attained with a broad range of Grignard reagents. This approach works well with both alkyl and aromatic Grignard reagents, thus providing a unified synthetic approach to privileged 2-substituted thiochroman-4-ones and a potential valuable precursor for further synthetic applications towards many pharmaceutically active molecules. The use of commercially available and/or readily prepared Grignard reagents will expedite the synthesis of a large library of both 2-alkyl substituted thiochroman-4-ones and thioflavanones for additional synthetic applications.