| Popis: |
Olefination of α-silyl-, α-phosphoryl- and α-stannyl-stabilised phosphonate carbanions derived from cyclo -[ l -AP4- d -Val] Li + 4b – d − allow a ( Z )-selective access to the α,β-substituted vinylphosphonates 7A – E that have been transformed into enantiomerically pure 4-alkylidene AP4 derivatives 12A , B and 13A , C . According to semi-empirical (PM3) calculations, the preference for like topologies in the intermediate adducts of the phosphonate addition step accounts for the highly ( Z )-selective course of the ‘tin-Peterson-like’ olefination. |
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