Abstract

Abstract

Palladium-catalyzed alkynylcarbonylation of aryl iodides was accomplished by using Mo(CO)₆ as a CO source. The reaction was conducted at room temperature with the use of tBu₃P as a ligand, which was found to be essential for smooth carbonylation. One-pot construction of pyrazoles by using aryl iodides with electron-withdrawing groups was also accomplished under these reaction conditions in the presence of methylhydrazine. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Lithiation chemistry has not been well explored in fluorous synthesis because of the lack of appropriate base-resistant fluorous tags; we recently developed a perfluoroalkylated arylsulfonyl tag for the protection of the indole ring nitrogen atom. Mesityllithium was found to be a suitable reagent for the α-lithiation of perfluoroalkyl-tagged 1-(arylsulfonyl)indole, and the fluorous synthesis of yuehchukene was accomplished efficiently using this method as a key step. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

In der organischen Synthesechemie werden Monometallspezies wie Organolithiumverbindungen seit langem für Deprotonierungsreaktionen genutzt. In den letzten Jahren ist mit den 'at-Komplexen eine neue Klasse von Metallierungsreagentien hinzugetreten, die das Syntheserepertoire metallorganischer Spezies ergänzt. Dank eines frei wählbaren Metallzentrums (Magnesium, Zink oder Aluminium), frei wählbarer Liganden (in Art und Anzahl) und eines frei wählbaren sekundären Metallzentrums (eines Alkalimetalls wie Lithium oder Natrium) sind 'at-Komplexe äußerst vielseitige basische Reagentien, deren synergetische Reaktionsweisen mit den homometallischen Magnesium-, Zink- oder Aluminiumverbindungen nicht beobachtet werden. Deprotonierungen mit metallorganischen 'at-Komplexen haben neue Perspektiven in der organischen Chemie eröffnet, mit ungewöhnlichen Reaktivitäten und manchmal unvorhergesehenen Regioselektivitäten.

Historically, single-metal organometallic species such as organolithium compounds have been the reagents of choice in synthetic organic chemistry for performing deprotonation reactions. Over the past few years, a complementary new class of metalating agents has started to emerge. Owing to a variable central metal (magnesium, zinc, or aluminum), variable ligands (both in their nature and number), and a variable second metallic center (an alkali metal such as lithium or sodium), “ate” complexes are highly versatile bases that exhibit a synergic chemistry which cannot be replicated by the homometallic magnesium, zinc, or aluminum compounds on their own. Deprotonation accomplished by using these organometallic ate complexes has opened up new perspectives in organic chemistry with unprecedented reactivities and sometimes unusual and unpredictable regioselectivities.

The addition of O- and N-nucleophiles to alkynes catalyzed by a phosphazene base, t-Bu-P4 base, was investigated. Alkynes were easily transformed to enol ethers and enamines in DMSO by the addition of nucleophiles. When phenylacetylene was reacted with diisopropylamine, a unique head-to-head dimerization of phenylacetylene was observed to give the enyne derivative. Terminal proton of phenylacetylene was also catalytically activated by t-Bu-P4 base to generate the acetylide anion which was reacted with carbonyl compounds to give phenylpropargylic alcohol derivatives.