The extension of the X-ray constrained (XC) wavefunction approach to open-shell systems using the unrestricted Hartree-Fock formalism is reported. The XC method is also extended to include relativistic effects using the scalar second-order Douglas-Kroll-Hess approach. The relativistic effects on the charge and spin density on two model compounds containing the copper and iron atom are reported. The size of the relativistic effects is investigated in real and reciprocal space; in addition, picture-change effects are investigated and discussed for the isolated Cu atom. It is found that the relativistic terms lead to changes in the densities that are much smaller than those from the X-ray constraint. Nevertheless, the use of the relativistic corrections in the ab initio model always leads to an improvement in the agreement statistics. An interesting result of the unrestricted XC technique is the possibility of obtaining experimentally derived spin densities from X-ray data.
D-Lyxose derived nitrone 7 was found to effectively undergo an SmI 2 -mediated radical addition to methyl acrylate affording γ-N-hydroxylamino ester 8 with high diastereomeric control. The pyrrolidinone 9 was prepared in a single step from 8 involving N-O bond cleavage with Zn/AcOH and subsequent spontaneous cyclization. D-Xylose derived nitrone 10 afforded in the SmI 2 -induced coupling with methyl acrylate the γ-N-hydroxylamino ester 11 as minor product. The major product the nitrone 12 is formed by unusual reductive deoxygenation of the starting nitrone.
Key indicatorsSingle-crystal X-ray study T = 295 K Mean (C-C) = 0.003 Å R factor = 0.056 wR factor = 0.169 Data-to-parameter ratio = 13.8For details of how these key indicators were automatically derived from the article, see
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