EXO AND ENDO 1,7-DIMETHYL-3,5,10-TRIOXATRICYLO[5.2.1.0(2,6)]DEC-8-EN-4-ONE - STRUCTURAL-ANALYSIS

C9H10O4, M(r) = 182.2; exo diasterecoisomer (1), orthorhombic, P2(1)2(1)2(1), a = 5.567 (3), b = 11.808 (5), c = 13.585 (5) angstrom, V = 893 (1) angstrom 3, Z = 4, D(m) = 1.33 (3), D(x) = 1.35 Mg m-3, lambda(Mo K-alphaBAR) = 0.7107 angstrom, mu = 1.00 mm-1, F(000) = 384, T = 298 K, final R = 0.047 for 1041 reflections; endo diastereoisomer (2), orthorhombic, Pbca, a = 14.339 (3), b = 10.499 (5), c = 11.637 (3) angstrom, V = 1751 (1) angstrom 3, Z = 8, D(m) = 1.36 (4), D(x) = 1.38 Mg m-3, lambda(Mo K-alphaBAR) = 0.7107 angstrom, mu = 1.00 mm-1, F(000) = 768, T = 298 K, final R = 0.074 for 1090 reflections. Within the scope of our studies on the stereochemical aspects of the Diels-Alder reaction, the two diastereoisomers of 1,7-dimethyl-3,5,10-trioxatricyclo[5.2.1.0(2.6)]dec-8-en-4-one, have been synthetized by reaction between 2,5-dimethylfuran and vinylene carbonate. The two structures are compared with those of bicyclo[2.2.1]-heptene-2,3-dicarboxylic anhydride homologs.