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제124회 대한화학회 학술발표회, 총회 및 기기전시회 안내 Enantioselective Oxygenative Arylation of Ynamides Employing Chiral N-Oxides

2019년 8월 29일 17시 56분 52초
ORGN.P-447 이곳을 클릭하시면 발표코드에 대한 설명을 보실 수 있습니다.
10월 18일 (금요일) 11:00~12:30
Organic Chemistry
저자 및
Tae-Woong Um, Girim Lee, Seunghoon Shin*
Department of Chemistry, Hanyang University, Korea

Synthesis of α-aryl carbonyl compounds is important because an array of natural products and pharmaceutically relevant molecules contain this moiety.1 The introduction of aryl groups at the α-position of carbonyl compounds was initially addressed in the Pd-catalyzed cross-coupling of enolate species with aryl halides.2 However, strong base involved limited their applications in the synthesis of tertiary α-arylated carbonyl compounds, due to a facile racemization of the product.3 A potential solution to this synthetic problem has recently emerged, employing Brønsted acid-catalyzed oxygenative arylation of ynamides.4 These processes occur under mildly acidic conditions, and thus the racemization can be kept to a minimum. We introduce an external oxidant. Herein, we report a reagent-controlled enantioselective oxidation reaction, using a chiral N,N’-dioxide. In this external oxidant approach, unmodified nucleophilic arenes could be employed and the product is now free of trace groups from the oxidant, thereby avoiding two unnecessary steps. Furthermore, the byproduct of the oxidation (mono-N-oxide) could be recycled at the end in an efficient manner. Various nucleophilic arenes, including indoles, phenols, and pyrroles, participate in the oxygenative alkylation, and enantioselectivity upto 92%ee was realized. Reference 1. Bellina, F.; Rossi, R. Chem. Rev. 2010, 110, 1082-1146. (b) Johansson, C. C. C.; Colacot, T. J. Angew. Chem. Int. Ed. 2010, 49, 676-707. 2. Hamann, B. C.; Hartwig, J. F. J. Am. Chem. Soc. 1997, 119, 12382-12383. 3. Chae, J.; Yun, J.; Buchwald, S. L. Org. Lett. 2004, 6, 4809-4812. 4. (a) Kaldre, D.; Maryasin, B.; Kaiser, D.; Gajsek, O.; González, L.; Maulide, N., Angew. Chem. Int. Ed. 2017, 56, 2212-2215. (b) Kaldre, D.; Maulide, N. Science, 2018, 361, 664-667.