CHED 508 |
| Beginning with the dehydration resistant aryl pyran pseudoacid, 4,4-dimethyl-3-hydroxydihydroisobenzopyran-1-one, we have synthesized and determined the structures of several pseudoacyl derivatives. These include the pseudoacyl halide, pseudoesters, pseudoamides with exocyclic and endocyclic nitrogens, and pseudoacyl anhydrides. This series contains a range of exocyclic substituents which are compared and contrasted with the endocyclic pseudoacyl system, which produces considerable variation in the endocyclic C-O bond lengths. At the extremes are the pseudoacyl chloride, 4,4-dimethyl-3-chlorodihydroisobenzopyran-1-one and the tertiaryl pseudoamide, 4,4-dimethyl-3-morpholinodihydroisobenzopyran-1-one. The pseudoacyl chloride crystallizes in the monoclinic system, space group P2(1)/n, with a = 7.8896(2)Å, b = 12.1750(3)Å, c = 10.7140(3)Å, beta = 99.477(3)o, V = 1015.10(9)Å3, and has C-O distance 1.411(2)Å. The tertiaryl pseudoamide crystallizes in the monoclinic system, space group P2(1)/c, with a = 6.2351(4)Å, b = 14.6502(10)Å, c = 15.2232(10)Å, beta = 96.215(6)o, V = 1382.39(16)Å3, and has C-O distance 1.474(2)Å. Consistent with this trend are the locations of the pseudoacyl H resonances, which shifts from 6.1 in the chloride to 4.8 in the amide. This study represents a detailed systematic examination of an arylpyranoid pseudoacyl structures. We acknowledge the support of NSF grant MRI 0618148 and the W. M. Keck Foundation for crystallographic resources. |
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Undergraduate Research Poster Session: Organic Chemistry
11:00 AM-1:00 PM, Monday, April 7, 2008 Morial Convention Center -- Hall A, Poster
Division of Chemical Education |