Computational studies on the asymmetric induction in intramolecular 1,3-dipolar cycloaddition of (S)-5-phenyl-morpholin-2-one

✍ Scribed by Michael G.B. Drew; Laurence M. Harwood; David W. Price; M.-S. Choi; Gyoosoon Park

• Publisher: Elsevier Science
• Year: 2000
• Tongue: French
• Weight: 278 KB
• Volume: 41
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)00777-2

✦ Synopsis

The intramolecular 1,3-dipolar cycloaddition reactions of chiral morpholinone-derived azomethine ylides with tethered alkenes and alkynes have been investigated by semi-empirical methods and ab initio quantum mechanics. The observed ecient direction of the asymmetric induction in the 1,3-dipolar cycloaddition has been modelled from a comparison of the energies of the four possible transition states arising from addition to either face of E-or Z-con®gured ylides. In the reaction of morpholinone with hex-5-enal, the most favourable transition state is shown to be the anti-addition to the E-ylide (E act $12 kcal/ mol by HF/3-21G). By contrast, reaction with hex-5-ynal led to anti-addition from the Z-ylide (E act $19 kcal/mol by HF/3-21G) exhibiting the lowest transition state energy. The resulting trends of relative transition state energy are in excellent agreement with the experimental observations.