ABSTRACT
Phosphole-containing π-systems have emerged as building blocks with enormous potential as electronic materials because of the tunability of the phosphorus center. Among these, asymmetric P-bridged trans-stilbenes are still rare, and here an elegant and efficient synthesis toward such fluorescent molecular frameworks is described. Fine-tuning of the photophysical properties is attempted by enforcing the planarization of the phosphorus tripod and thus increasing the interaction between the phosphorus lone pair and the π-system. The electronic structure of the π-conjugated frameworks is analyzed with NMR, UV-vis and fluorescence spectroscopy, and time-dependent density functional theory (TD-DFT) calculations.
ABSTRACT
Alkylidenepyrrolidines 1, 21, 24 and 26 undergo reactions with nitrile oxides and nitrilimines or their precursors to give a range of novel heterocyclic compounds. With alkylidenepyrrolidine ester 1, nitrolic acids give products in which the liberated nitrous acid reacts with the alkylidenepyrrolidine, followed by two cycloadditions to give adducts 3. In contrast, hydroximoyl chlorides give isoxazoles 10, presumably by cycloaddition/elimination. With hydrazonyl chlorides, simple acylation of the alkylidenepyrrolidine occurs to give compounds 17. With sulfonyl alkylidenepyrrolidines 24 and 26, cycloaddition onto the imine tautomer is the preferred pathway, with a stereoselective reaction taking place in the latter case.
