Chemoselective hydrosilylation of functionalized alkenes is difficult to achieve using base-metal catalysts. Reported herein is that well-defined bis(amino)amide nickel pincer complexes are efficient catalysts for anti-Markovnikov hydrosilylation of terminal alkenes with turnover frequencies of up to 83,000 per hour and turnover numbers of up to 10,000. Alkenes containing amino, ester, amido, ketone, and formyl groups are selectively hydrosilylated. A slight modification of reaction conditions allows tandem isomerization/hydrosilylation reactions of internal alkenes using these nickel catalysts.
The first efficient and non‐precious nanoparticle catalyst for alkene hydrosilylation with commercially relevant tertiary silanes has been developed. The nickel nanoparticle catalyst was prepared in situ from a simple nickel alkoxide precatalyst Ni(OtBu)2⋅x KCl. The catalyst exhibits high activity for anti‐Markovnikov hydrosilylation of unactivated terminal alkenes and isomerizing hydrosilylation of internal alkenes. The catalyst can be applied to synthesize a single terminal alkyl silane from a mixture of internal and terminal alkene isomers, and to remotely functionalize an internal alkene derived from a fatty acid.
Few chemical methods exist for the
covalent conjugation of two
proteins. We report the preparation of site-specific protein–protein
conjugates that arise from the sequential cross-coupling of cysteine
residues on two different proteins. The method involves the synthesis
of stable palladium–protein oxidative addition complexes (Pd-protein
OACs), a process that converts nucleophilic cysteine residues
into an electrophilic S-aryl-Pd-X unit by taking advantage of
an intramolecular oxidative addition strategy. This process
is demonstrated on proteins up to 83 kDa in size and can be conveniently
carried out in water and open to air. The resulting Pd-protein OACs
can cross-couple with other thiol-containing proteins to arrive at
homogeneous protein–protein bioconjugates.
Me2SiH2, MeSiH3, and SiH4 are gaseous and flammable silanes that are inconvenient to use in chemical reactions. Catalytic amounts of a nickel pincer complex and NaO(t)Bu are reported to allow the synthesis of alkyl hydrosilanes from alkenes and alkoxy hydrosilanes, leading to the replacement of Me2SiH2, MeSiH3, and SiH4 by Me2(MeO)SiH, Me(EtO)2SiH, and (MeO)3SiH in hydrosilylation reactions of alkenes. The scope and mechanism of the reactions are also described.
The
phosphoinositide 3-kinase (PI3K)/mechanistic target of rapamycin
(mTOR) pathway is a critical regulator of cell growth and is frequently
hyperactivated in cancer. Therefore, PI3K inhibitors represent a valuable
asset in cancer therapy. Herein we have developed a novel anticancer
agent, the potent pan-PI3K inhibitor PQR514 (4), which
is a follow-up compound for the phase-II clinical compound PQR309
(1). Compound 4 has an improved potency
both in vitro and in cellular assays with respect to its predecessor
compounds. It shows superiority in the suppression of cancer cell
proliferation and demonstrates significant antitumor activity in an
OVCAR-3 xenograft model at concentrations approximately eight times
lower than PQR309 (1). The favorable pharmacokinetic
profile and a minimal brain penetration promote PQR514 (4) as an optimized candidate for the treatment of systemic tumors.
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