Direct methylidenation of carbonyl compounds represents an appealing route to terminal alkenes. Existing methods for this transformation typically rely on stoichiometric phosphorus ylides (methylene Wittig) or organotitanium complexes (Tebbe or Petasis reagents). Here, we report a Cp2TiCl2-catalyzed method that uses CH2Br2 as a readily available carbene precursor and Zn as the reductant for methylidenation of alkyl ketones. The reaction is proposed to proceed via the in situ generation of an alkyl–Zn species, which then generates a Ti–carbene intermediate. Alkali metal salts, such as KBF4 and LiPF6, improve the reaction efficiency. Cyclic voltammetry studies implicate the alkali metal ions in promoting dissociation of chloride from Ti and enhancing reactivity with the alkyl–Zn reagent. The resulting protocol is operationally simple and offers a practical alternative to the use of stoichiometric methylidenation reagents.
Radical-mediated transition-metal-catalyzed C─H carbonylation represents a direct and powerful approach for the synthesis of carbonyl compounds; however, the stoichiometric oxidants typically required for hydrogen atom abstraction hamper the extensive application of these protocols and raise environmental concerns. In...
Cheng-Cheng Fan, Jia-Ning Wu, Peng Wang et al.· Angewandte Chemie· 0 citations
Direct activation of native C(sp2)–NH2 bonds in alkenyl amines remains a largely unmet challenge in cross-coupling chemistry owing to their high bond dissociation energies, poor leaving-group ability, and competing tautomerization pathways. Herein, we report a nickel-catalyzed tandem deaminative coupling/alkene isome...
We have developed an efficient protocol for the selective oxidation of arylmethyl halides to aromatic carbonyl compounds. This transformation employs tetraphenylphosphonium bromide (Ph4PBr) as both an oxidant and phase-transfer catalyst (PTC), in combination with EDTA and CaF2 as cocatalysts. Under mild reaction condit...
Xian-Wei Xu, Si-Da Li, Xin-Cheng Liu et al.· Molecules· 0 citations
The use of ester-derived electrophiles in transition-metal-free electroreductive C(sp3)─C(sp3) bond formation remains largely unexplored. Herein, we report a sacrificial-anode-enabled electroreductive cross-coupling of simple unsaturated carboxylates with unactivated alkyl halides. Aryl, alkenyl, and alkynyl carboxylat...
Palladium(II) complexes of the TPA family (TPA = tris(2-pyridylmethyl)amine) catalyze selective C(sp3)-H oxyfunctionalizations but have so far been unable to activate "green" oxidant H2O2, instead requiring peroxycarboxylic acids (2-4 equiv, best results coming with m-CPBA). Herein, we show that hydrogen peroxide itsel...
D. P. Lubov, Elizaveta M. Zhernikova, K. Bryliakov· Organic Letters· 0 citations
The SN2 reaction constitutes one of the most fundamental bond-forming transformations in organic chemistry, finding numerous synthetic applications across pharmaceutical, agrochemical, and materials science. However, the development of new catalysts for asymmetric SN2 reactions with nucleophiles beyond enolate deriva...
Yi-Qun Zeng, Yang Yu, Xiang-Yuan Liu et al.· Journal of the American Chem...· 0 citations
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