| Abstract
| - The Diels−Alder reaction of 3-vinylfurans 5 and27 with DMAD, N-phenylmaleimide, anddimethylmaleate afforded products derived both from addition to the furan ringdiene system (intraannularaddition) and to the furan 2,3-double bond 3-vinyl group diene system(extraannular addition).For example, compounds 6 and 7 were obtainedfrom 5 and DMAD. In contrast, dienophilescontaining a phenylsulfinyl group, such as19−21, gave products derived exclusively fromtheextraannular reaction mode. These products are useful precursorsof 4-substituted benzofurans,especially 4-hydroxybenzofurans.
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