Toward the development of a structurally novel class of chiral auxiliaries. Conformational properties of the aldol adducts of oxadiazinones: observation of unusual shielding effects |
| |
Authors: | Burgeson James R Renner Matthew K Hardt Ingo Ferrence Gregory M Standard Jean M Hitchcock Shawn R |
| |
Institution: | Department of Chemistry, Illinois State University, Normal, Illinois 61790-4160, USA. |
| |
Abstract: | Asymmetric aldol reactions were conducted with the titanium enolate of N(3)-hydrocinnamoyl-3,4,5,6-tetrahydro-2H-1,3,4-oxadiazin-2-one to afford aldol adducts 5a-j. The dominant product of the asymmetric aldol reaction was the non-Evans syn adduct as determined by (1)H NMR spectroscopy and X-ray crystallography. When evaluating the (1)H NMR spectra of adducts 5a-j, a highly shielded signal with an average chemical shift of 0.05 ppm was observed. This signal was readily determined to be the C(5)-methyl group of the oxadiazinone. It is presumed that the overall conformation adopted by the aldol adducts in solution places an aromatic ring of the N(3)-substituent in close proximity to the C(5)-methyl group. An investigation of this conformational preference is conducted employing (1)H NMR spectroscopy, X-ray crystallography, and computational methods. |
| |
Keywords: | |
本文献已被 PubMed 等数据库收录! |
|