Asymmetric Diels–Alder reactions of 5-substituted and 5,6-disubstituted (S)-2-(p-tolylsulfinyl)-1,4-benzoquinones with cyclopentadiene and trans-piperylene
摘要:
A systematic study of reactions between 5-substituted and 5,6-disubstituted (S)-2-p-tolylsulfinyl-p-benzoquinones and cyclopentadiene or trans-piperylene is reported. Complete regio and pi-facial selectivities are observed. The different behaviours of cyclic and acyclic dienes in the presence of ZnBr2 (cyclopentadiene showed reversed diastereoselection) and the role of BF3 . OEt2 are discussed. (C) 1999 Elsevier Science Ltd. All rights reserved.
Regio- and stereoselectivity in Diels–Alder reactions of 1,2-disubstituted dienes with enantiopure (SS)-(p-tolylsulfinyl)-1,4-benzoquinones
作者:M.Carmen Carreño、José L Garcı́a Ruano*、Cynthia Z Remor、Antonio Urbano
DOI:10.1016/s0957-4166(00)00365-7
日期:2000.11
Reactions of 1,2-disubstituteddienes 1–3 with enantiopure sulfinylquinones 4–6 occur with similar π-facial diastereoselectivities but reversed regiochemistry under thermal conditions and in the presence of ZnBr2. After spontaneous elimination of the sulfoxide, optically active polycyclic dihydroquinones are formed with ees ranging from 36 to >97%. The regiochemistry of the process is controlled by