Cationic Cobalt Porphyrin-Catalyzed Allylation of Aldehydes with Allyltrimethylsilanes

Advancements in Desilylation Reactions for the Synthesis of Valuable Organic Molecules

Silicon, due to its abundance, non-toxicity, and cost-effectiveness, is a critical element in the earth's crust with significant industrial applications. In organic chemistry, main group elements, and in particular silicon, are extensively utilized as versatile synthetic intermediates. Despite the current challenges associated with harsh reaction conditions and unsustainable practices in synthesizing crucial organic structural molecules, desilylation reactions have emerged as a facilitative method, offering milder conditions and operational simplicity. This review provides a comprehensive analysis of recent advancements in the synthesis of valuable organic molecules through two distinct desilylation reactions. It systematically presents the synthesis of a variety of derivatives, such as furan, alcohol, N-heterocyclic, and ketone, highlighting the broad substrate tolerance of these reactions. This broad functional group compatibility suggests a promising future for the synthesis of a wide range of bioactive molecules, underscoring the significant potential of desilylation in contemporary organic synthesis.

Stepwise N-Methylation of Ruthenium and Cobalt 5,15-Diazaporphyrins: Post-Functionalization of Porphyrinoid Catalysts

Post-functionalization of porphyrinoid catalysts provides a powerful tool for fine-tuning their electronic structure. We have succeeded in the stepwise methylation of the peripheral nitrogen atoms in ruthenium and cobalt 5,15-diazaporphyrins. The axial coordination of an anion to the metal center accelerates the second methylation through charge neutralization. N-Methylation of the diazaporphyrin complexes effectively controls their electron deficiency, Lewis acidity, and catalytic activity.

MnO2 as a terminal oxidant in Wacker oxidation of homoallyl alcohols and terminal olefins

Efficient and mild reaction conditions for Wacker-type oxidation of terminal olefins of less explored homoallyl alcohols to β-hydroxy-methyl ketones have been developed by using a Pd(ii) catalyst and MnO2 as a co-oxidant. The method involves mild reaction conditions and shows good functional group compatibility along with high regio- and chemoselectivity. While our earlier system of PdCl2/CrO3/HCl produced α,β-unsaturated ketones from homoallyl alcohols, the present method provided orthogonally the β-hydroxy-methyl ketones. No overoxidation or elimination of benzylic and/or β-hydroxy groups was observed. The method could be extended to the oxidation of simple terminal olefins as well, to methyl ketones, displaying its versatility. An application to the regioselective synthesis of gingerol is demonstrated.

Recent advances in cobalt-catalyzed allylic functionalization

Unlike many other state-of-the-art transition-metal-catalyzed allylic substitutions, cobalt-catalyzed allylic substitution has received much less attention from synthetic chemists for a long time despite the fact that cobalt is an earth-abundant, low-cost and thus much more sustainable option as either a reagent or a catalyst in organic synthesis. Recently, there has been an upsurge in the use of cobalt catalysis in allylic functionalization reactions, including allylic substitution, nucleophilic allylation, and Heck-type allylic functionalization, to construct synthetically significant building blocks featuring a double bond available for diverse downstream synthetic manipulations. This review highlights the current development of cobalt catalysis in allylic functionalization with an in-depth discussion of the reaction scope and mechanistic insights.

A highly efficient Hg(OTf)2-mediated Sakurai–Hosomi allylation of N-tert-butyloxycarbonylamino sulfones, aldehydes, fluoroalkyl ketones and α,β-unsaturated enones using allyltrimethylsilane

The cheap and easily available Hg(OTf)₂ can efficiently mediate the Sakurai–Hosomi reaction of N-Boc amino sulfones, aldehydes, α-fluoroalkyl ketones and α,β-unsaturated enones using allyltrimethylsilane with the catalyst loading down to 0.5–5.0 mol%.