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  • 09월 05일 17시 이후 : 초록수정 불가능, 일정확인 및 검색만 가능

제120회 대한화학회 학술발표회, 총회 및 기기전시회 안내 COBI-catalyzed enantioselective synthesis of cyclopropane and its retro-Claisen rearrangement to 2,5-dihydrooxepine

2017년 8월 31일 16시 33분 28초
ORGN.P-442 이곳을 클릭하시면 발표코드에 대한 설명을 보실 수 있습니다.
10월 20일 (금요일) 13:00~14:30
Organic Chemistry
저자 및
Su Yong Shim, Cho Soo Min, do hyun ryu*
Department of Chemistry, Sungkyunkwan University, Korea

Over the past decades, considerable attention has been devoted to the development of asymmetric methodologies for the synthesis of cyclopropane derivatives. However, the examples of enantioselective cyclopropanation reactions via Michael-Initiated Ring Closure (MIRC) between α,β-unsaturated aldehyde and diazo compounds are uncommon. Recently, we developed chiral oxazaborolidinium ion (COBI) catalyzed enantioselective cyclopropanation of α- or α,β-substituted acroleins with various α-alkyl diazo compounds providing highly functionalized cyclopropane compounds with excellent trans/cis ratio (>20:1) and stereoselectivity (up to >99% ee). The synthetic utility of this methodology was demonstrated in the first total synthesis and absolute structure determination of Hamavellone B exhibiting antimalarial activity. We envisaged that this approach could be extended to enantioselective synthesis of 2,5-dihydrooxepine. While 2,5-dihydrooxepine has been synthesized by retro-Claisen rearrangement of the corresponding vinylcyclopropylcarboxaldehyde, examples of asymmetric synthesis of 2,5-dihydrooxepines using this approach are rare due to the multiple steps required for the preparation of the chiral vinylcyclopropylcarboxaldehyde. Here, we report COBI-catalyzed enantioselective synthesis of 2,5-dihydrooxepine through tandem-cyclopropanation-retro-Claisen rearrangement with α-vinyl diazo compounds. A wild range of 2,5-dihydrooxepines with aliphatic and aromatic group were obtained in high yield (up to 86%) and excellent enantioselectivity (up to >99% ee).