Diels-Alder reactions of 1,2-(1,1'-binaphthalene-2,2'-diyldisulfonyl)ethylene with symmetrical and unsymmetrical dienes
摘要:
The C2-symmetrical chiral reagent 1,2-(1,1'-binaphthalene-2,2'-diyldisulfonyl)ethylene (1) is a reactive dienophile and forms Diels-Alder adducts with symmetrical and unsymmetrical dienes. In the case of unsymmetrical dienes the reaction affords, in most cases, a single diastereomeric adduct whose stereochemistry has been determined by NMR spectroscopy and confirmed by X-ray structure determination of selected adducts. The arylsulfonyl groups can be removed with formation of a double bond, making 1 a chiral synthetic equivalent of acetylene in [4 + 2]-cycloaddition reactions. The binaphthyl auxiliary can be recovered and recycled.
The first asymmetric Diels-Alder reactions of some 3- and 2-vinylindoles with (N-propenoyl)bomane-10,2-sultam are described. With one exception, the experimental results are indicative of a high pi-facial diastereoselectivity. Following a related procedure, 3-vinylindoles were also allowed to react with a racemic bis(naphthylsulfonyl)-dienophile to furnish tetrahydrocarbazoles with endo-diastereoselectivity.