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Tris(pentafluorophenyl)borane has been found to catalyze the two‐fold C(sp3)−H silylation of various trialkylamine derivatives with dihydrosilanes, furnishing the corresponding 4‐silapiperidines in decent yields. The multi‐step reaction cascade involves amine‐to‐enamine dehydrogenation at two alkyl residues and two electrophilic silylation reactions of those enamines, one inter‐ and one intramolecular. [ABSTRACT FROM AUTHOR]

Es wurde gefunden, dass Tris(pentafluorphenyl)boran die zweifache C(sp3)‐H‐Silylierung von mehreren Trialkylaminderivaten mit Dihydrosilanen katalysiert und die entsprechenden 4‐Silapiperidine in annehmbaren Ausbeuten ergibt. Die mehrstufige Reaktionsabfolge beinhaltet die Dehydrierung des Amins zum Enamin an zwei Alkylresten und zwei elektrophile (eine inter‐ und eine intramolekular) Silylierungen jener Enamine. [ABSTRACT FROM AUTHOR]

A copper-catalyzed C4-selective addition of silicon nucleophiles released from an Si-B reagent to prochiral pyridinium triflates is reported. The dearomatization proceeds with excellent enantioselectivity using Cu(CH 3 CN) 4 PF 6 as the precatalyst and (R,R)-Ph-BPE (1,2-bis[(2R,5R)-2,5-diphenylphospholan-1-yl]ethane) as the chiral ligand. A carbonyl group at C3 is required for this, likely acting a weak donor group to preorganize and direct the nucleophilic attack towards C4. The resulting 4-silylated 1,4-dihydropyridines can be further converted into functionalized piperidine derivatives., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

A four-step formal ipso allylation of benzoic acid derivatives involving a B(C 6 F 5 ) 3 -initiated and proton-catalyzed [1,2]-alkyl shift as part of a dehydrative coupling of cyclohexa-2,5-diene-1-carbaldehyde derivatives and 1,1-diarylalkenes is reported. By this, a series of allyl arenes can be regioselectively obtained from readily available benzoic acids in good yields.

Biocatalytic nucleoside (trans-)glycosylations catalyzed by nucleoside phosphorylases have evolved into a practical and convenient approach to the preparation of modified nucleosides, which are important pharmaceuticals for the treatment of various cancers and viral infections. However, the obtained yields in these reactions are generally determined exclusively by the innate thermodynamic properties of the nucleosides involved, hampering the biocatalytic access to many sought-after target nucleosides. We herein report an additional means for reaction engineering of these systems. We show how apparent equilibrium shifts in phosphorolysis and glycosylation reactions can be effected through entropically driven, biased esterification of nucleosides and ribosyl phosphates with inorganic borate. Our multifaceted analysis further describes the kinetic implications of this in situ reactant esterification for a model phosphorylase., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

White phosphorus (P 4 ) undergoes degradation to P 2 moieties if exposed to the new N,N-bis(silylenyl)aniline PhNSi 2 1 (Si=Si[N(tBu)] 2 CPh), furnishing the first isolable 2,5-disila-3,4-diphosphapyrrole 2 and the two novel functionalized Si=P doubly bonded compounds 3 and 4. The pathways for the transformation of the non-aromatic 2,5-disila-3,4-diphosphapyrrole PhNSi 2 P 2 2 into 3 and 4 could be uncovered. It became evident that 2 reacts readily with both reactants P 4 and 1 to afford either the polycyclic Si=P-containing product [PhNSi 2 P 2 ] 2 P 2 3 or the unprecedented conjugated Si=P-Si=P-Si=NPh chain-containing compound 4, depending on the employed molar ratio of 1 and P 4 as well as the reaction conditions. Compounds 3 and 4 can be converted into each other by reactions with 1 and P 4 , respectively. All new compounds 1-4 were unequivocally characterized including by single-crystal X-ray diffraction analysis. In addition, the electronic structures of 2-4 were established by Density Functional Theory (DFT) calculations., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Tris(pentafluorophenyl)borane has been found to catalyze the two-fold C(sp 3 )-H silylation of various trialkylamine derivatives with dihydrosilanes, furnishing the corresponding 4-silapiperidines in decent yields. The multi-step reaction cascade involves amine-to-enamine dehydrogenation at two alkyl residues and two electrophilic silylation reactions of those enamines, one inter- and one intramolecular., (© 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

A trityl-cation-initiated annulation of benzyl-substituted vinylcyclopropanes (VCPs) with hydrosilanes is reported. Two Si-C(sp 3 ) bonds and one C(sp 2 )-C(sp 3 ) bond are formed in this process where an intramolecular 6- endo-tet Friedel-Crafts alkylation of a silylium-ion-activated cyclopropane ring is the rate-determining key step. The reaction mechanism is proposed based on computations and is in agreement with experimental observations. The new reaction leads to an unprecedented silicon-containing 6/6/5-fused ring system. A phenethyl-substituted VCP derivative yields another unknown tricycle having 6/6/6 ring fusion by reacting in a related but different way involving a 6- exo-tet ring closure., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The transition-metal-free hydroboration of various alkenes with pinacolborane (HBpin) initiated by tris[3,5-bis(trifluoromethyl)phenyl]borane (BAr F 3 ) is reported. The choice of the boron Lewis acid is crucial as the more prominent boron Lewis acid tris(pentafluorophenyl)borane (B(C 6 F 5 ) 3 ) is reluctant to react. Unlike B(C 6 F 5 ) 3 , BAr F 3 is found to engage in substituent redistribution with HBpin, resulting in the formation of Ar F Bpin and the electron-deficient diboranes [H 2 BAr F ] 2 and [(Ar F )(H)B(μ-H) 2 BAr F 2 ]. These in situ-generated hydroboranes undergo regioselective hydroboration of styrene derivatives as well as aliphatic alkenes with cis diastereoselectivity. Another ligand metathesis of these adducts with HBpin subsequently affords the corresponding HBpin-derived anti-Markovnikov adducts. The reactive hydroboranes are regenerated in this step, thereby closing the catalytic cycle., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The effect of carbon is subtle but sweet: The flexible C-linkage in the newly synthesised C-glycosyl mimetic, Manalpha(1,6)-C-ManalphaOPh allows OH--pi bonding, both in the gas phase and in aqueous solution. This interaction is absent in the O-linked disaccharide (see figure).The intrinsic conformational preference of a newly synthesised glycomimetic, the C-linked disaccharide Manalpha(1,6)-C-ManalphaOPh (1), has been determined in the gas phase at about 10 K by infrared ion dip spectroscopy coupled with density functional theory and ab initio calculations, and compared with its dynamical conformation in aqueous solution at 298 K by NMR spectroscopy. Comparisons are also made between these conformations and those of the corresponding O-linked disaccharide 2 in the gas phase and the C-linked disaccharide Manalpha(1,6)-C-ManalphaOMe (3) in the gas phase and in aqueous solution. The C- and O-linked disaccharides 1 and 2 present quite distinct conformational preferences in the gas phase: inter-glycosidic hydrogen bonding, seen in one of the two conformers populated in 2, is not seen in 1 which adopts a conformation (not populated in 2) with glycosidic dihedral angles (phi, psi, omega) of -72 degrees , 52 degrees and 66 degrees ; supported in part by an OH--pi hydrogen bond. This conformer is also strongly populated in an aqueous solution of 1 (and very weakly, of 3) together with a second conformer, with dihedral angles (phi, psi, omega) of about -60 degrees , 180 degrees and 60 degrees , not seen in the gas phase but by far the dominant conformer in an aqueous solution of 3. The C-disaccharide 1 was tested as a potential inhibitor, but displayed no significant inhibitory activity against Jack Bean alpha-mannosidase.