1,4-Pentenyne as a Five-Carbon Synthon for Efficient and Selective Syntheses of Natural Products Containing 2,4-Dimethyl-1-penten-1,5-ylidene and Related Moieties by Means of Zr-Catalyzed Carboalumination of Alkynes and Alkenes
作者:Gangguo Zhu、Ei-ichi Negishi
DOI:10.1002/chem.200701512
日期:2008.1
Two highly efficient protocols for enantioselective synthesis of 2,4-dimethyl-1-penten-1,5-ylidene derivatives involve the combined use of the Zr-catalyzed methylalumination of alkynes (ZMA) and the Zr-catalyzed asymmetric carboalumination of alkenes (ZACA). The ZMA/ZACA protocol has been applied to the synthesis of a nafuredin intermediate 14 and a potential intermediate 18 for milbemycin beta 3,
First total synthesis of the whole series of the antiostatins A and B
作者:Kerstin E. Knott、Stefan Auschill、Anne Jäger、Hans-Joachim Knölker
DOI:10.1039/b821039j
日期:——
The first synthesis of the whole antiostatin family is described by using an iron-mediated carbazole synthesis, regioselective nitration at C-4 and establishing 5-isobutyl-1-nitrobiuret as a reagent for introduction of the antiostatin B side chain at C-4.
作者:Giampaolo Giacomelli、Luciano Lardicci、Carlo Bertucci、Anna Maria Caporusso
DOI:10.1016/0040-4020(78)80111-2
日期:1978.1
The synthesis and the physical properties of some opticallyactive 1,4-dialkylbuta-1,3-dienes are reported. The synthetic processes employed were essentially stereospecific. NMR, UV and CD spectra of these compounds provide information on the main conformation of the conjugated diene system, which was shown to be s-trans planar.
Solvated rhodium atoms, prepared by the metal vapour synthesis technique, promote the silylformylaton reaction of variously substituted alkynes (RRCH)-R-1-C-2(CH2)(n)C equivalent to CH, with catalytic activities comparable with and even higher than more common species such as Rh-4(CO)(12). Z-Silylalkenals are exclusively formed in high yields (60-95%) indicating syn addition both of CO and of the silane (Me2PhSiH) to the triple bond, The chemoselectivity of the process (silylformylation vs. hydrosilylation) is highly affected by the amount of catalyst employed (mmol of Rh species with respect to the alkyne reagent), by the steric requirements of the acetylenic substrates and by the hydrosilane/alkyne molar ratio. When optically active acetylenes are treated in the presence of Me2PhSiH under carbon monoxide pressure, the silylformylation reaction occurs with total retention of stereochemistry of the stereogenic centre, even if it is at the alpha -position of the unsaturated moiety, to afford enantiomerically enriched beta -silylalkenals.
Caporusso, Anna Maria; Zoppi, Alessandra; Settimo, Federico Da, Gazzetta Chimica Italiana, 1985, vol. 115, # 5, p. 293 - 296
作者:Caporusso, Anna Maria、Zoppi, Alessandra、Settimo, Federico Da、Lardicci, Luciano