For examples of Diels-Alder reactions of cyclohexenecarboxaldehyde or its corresponding acetal to obtain cis-fused bicyclic ring system with all-carbon quaternary center on the bridgehead, see:
For examples of Diels-Alder reactions of cyclohexenecarboxaldehyde or its corresponding acetal to obtain cis-fused bicyclic ring system with all-carbon quaternary center on the bridgehead, see: (a) J. Szmuszkowicz, and E.D. Bergmann Bull. Res. Counc. Israel 3 1953 93 95
Most examples of tetrasubstituted cyclic dienophiles are limited to quinone and maleic anhydride derivatives. For examples, see
Most examples of tetrasubstituted cyclic dienophiles are limited to quinone and maleic anhydride derivatives. For examples, see: (a) O. Kwon, S.B. Park, and S.L. Schreiber J. Am. Chem. Soc. 124 2002 13402 13404
3OH, room temperature, 2 h, 94%). For details, see Experimental section.
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note
The operative dienophile formally corresponds to either (i) or (ii), in principle derivable from the thermolysis of 11 via cyclization, tautomerization, and dehydration in a sequence, which has not been defined.
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(a) M. Koprowski, A. Skowrońska, M.L. Glówka, and A. Fruziński Tetrahedron 63 2007 1211 1228
13C NMR. For the analytical data of the cis-isomers, see Ref. 3c. In accord with Casadevall's observation, the ring junction carbons of trans-fused 30a and 31a are more deshielded than those of cis-fused 30b and 31b
13C NMR. For the analytical data of the cis-isomers, see Ref. 3c. In accord with Casadevall's observation, the ring junction carbons of trans-fused 30a and 31a are more deshielded than those of cis-fused 30b and 31b: P. Metzger, E. Casadevall, and M.J. Pouet Org. Magn. Reson. 19 1982 229 234