63591-90-2Relevant academic research and scientific papers
Highly efficient one-pot double-Wittig approach to unsymmetrical (1Z,4Z,7Z)-homoconjugated trienes
Pohnert, Georg,Boland, Wilhelm
, p. 1821 - 1826 (2007/10/03)
We describe a novel one-pot double-Wittig approach towards unsymmetrically substituted skipped trienes using the symmetrical (Z)-hex-3- ene-1,6-bis(triphenylphosphonium iodide) (2) as key reagent. Double alkenylation of the corresponding bis(ylide) 3 with sequentially added aldehydes gives (Z)-1,4,7-homoconjugated trienes in good yields. Dissymmetrization of the bis(ylide) 3 is feasible, since it displays enhanced reactivity compared to the monoylide resulting from the first olefination. Symmetrical products from statistical coupling of the bis(ylide) 3 can be drastically suppressed by slow release of the first aldehyde component through in situ thermal decomposition of an intermediate aluminate complex, generated by reduction of a methyl ester with DIBAL-H. The novel strategy is successfully applied to the one-pot synthesis of functionalized and isotopically labelled polyunsaturated fatty acids as well as to the synthesis of the geometrid moth pheromone (3Z,6Z,9Z)-nonadeca-1,3,6,9-tetraene (6a). The dissymmetrization strategy was also found to be suitable for the synthesis of homoconjugated dienes from 1,3-propylbis(triphenylphosphonium bromide).
Beyond the cyanine limit: Peierls distortion and symmetry collapse in a polymethine dye
Tolbert, Laren M.,Zhao, Xiaodong
, p. 3253 - 3258 (2007/10/03)
Theory predicts that cyanine dyes and related linear systems undergo symmetry collapse and bond localization at long chain lengths. Beyond this 'cyanine limit', the properties of these systems do not extrapolate from their shorter counterparts. To test this prediction, dipyridocyanines have been synthesized and shown to undergo such symmetry collapse with chain lengths as short as 13.
