Quantum chemical modeling of chiral catalysis. Part 18. Conformational studies on chiral N-sulfonylated 1,3,2-oxazaborolidines and related aldehyde complexes potentially involved in the catalytic asymmetric diels-alder reactions
✍ Scribed by Vesa Nevalainen
- Publisher
- Elsevier Science
- Year
- 1994
- Tongue
- English
- Weight
- 502 KB
- Volume
- 5
- Category
- Article
- ISSN
- 0957-4166
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✦ Synopsis
Properties of Lewis acidic oxazaborolidines 1 were investigated by means of ab initio MO methods (RHF, Ksulfonylated 1,3,2-oxazaborolidine 1' as a model). Energies of the coordination of aldehydes to 1 were estimated by using formaldehyde and acrolein adducts of 1' as models. Energies (MP2/6-31G//6-31G) of the coordination of formaldehyde to 1' were -1 kJ mol-J (2'b; axial S=O) and +26 kI mol-1 (2'a; equatorial S=O). The corresponding energies of the formation of acrolein adducts (3'a and 3'b, both s-mans, equatorial S=O) were higher, +43 kJ mol-J (vinyl equatorial) and +54 kJ mol-J (vinyl axial). An s-cis conformer of 3'a was found to be unstable.