Sodium and potassium derivatives of diphenyl(trimethylsilyl)methane

Reactions of Sodium Diisopropylamide: Liquid-Phase and Solid-Liquid Phase-Transfer Catalysis by N,N,N',N″,N″-Pentamethyldiethylenetriamine

Sodium diisopropylamide (NaDA) in N,N-dimethylethylamine (DMEA) and DMEA-hydrocarbon mixtures with added N,N,N',N″,N″-pentamethyldiethylenetriamine (PMDTA) reacts with alkyl halides, epoxides, hydrazones, arenes, alkenes, and allyl ethers. Comparisons of PMDTA with N,N,N',N'-tetramethylethylenediamine (TMEDA) accompanied by detailed rate and computational studies reveal the importance of the trifunctionality and κ2-κ3 hemilability. Rate studies show exclusively monomer-based reactions of 2-bromooctane, cyclooctene oxide, and dimethylresorcinol. Catalysis with 10 mol % PMDTA shows up to >30-fold accelerations (kcat > 300) with no evidence of inhibition over 10 turnovers. Solid-liquid phase-transfer catalysis (SLPTC) is explored as a means to optimize the catalysis as well as explore the merits of heterogeneous reaction conditions.

Palladium-Catalyzed Direct Arylation of 2-Pyridylmethyl Silanes with Aryl Bromides

The first palladium-catalyzed direct arylation of 2-pyridylmethyl silanes with aryl bromides to generate a diverse array of aryl(2-pyridyl)-methyl silane derivatives has been developed. This protocol facilitates access to various kinds of heterocycle-containing silanes in good to excellent yields (40 examples, 66-97% yield) with good functional group tolerance. The scalability of this transformation is demonstrated.

50 years of superbases made from organolithium compounds and heavier alkali metal alkoxides

A review of reactions of organolithium compounds (RLi) with alkali metal alkoxides is presented. On the one hand, simple lithium alkoxides form adducts with RLi the reactivity of which differs only slightly from that of RLi. On the other hand, after mixing heavier alkali metal alkoxides (R’OM, M = Na, K, Rb, Cs) with RLi, a new system is formed, which has reactivity that dramatically exceeds that of the parent RLi. A metal interchange, according to the equation RLi + R’OM = RM + R’OLi, occurs in this system, giving rise to a superbase. This reaction is frequently used for the preparation of heavier alkali metal organometallic compounds. Similar metal interchange takes place between R’OM and compounds such as lithium amides and lithium enolates of ketones or esters, thus demonstrating the general nature of this procedure. Superbases react easily with many types of organic compounds (substrates), resulting in the formation of a heavier alkali metal derivative of the substrate (metalation). The metalated substrate can react in situ with an electrophile to yield the substituted substrate, a procedure that is frequently used in synthetic and polymer chemistry. An improved mechanism of metal interchange and reaction of superbases with substrates is proposed.