Synthesis of methyl ketones from terminal olefins using PdCl2/CrO3 system mimicking the Wacker process

Palladium-Catalyzed Oxidant Dependent Switchable Aza-Wacker Cyclization and Oxidative Dimerization of Benzimidates

An oxidant dependent switchable palladium-catalyzed synthesis of 1,3-oxazines and benzohydrazonates (azines) from O-homoallyl benzimidates has been developed. The reaction involved aza-Wacker-type intramolecular cyclization of O-homoallyl benzimidates with Cu(OAc)2 as oxidant under Pd-catalysis to deliver 4-methylene-1,3-oxazines, whereas dimerization of O-homoallyl benzimidates with K2S2O8 as oxidant resulted remarkably in benzohydrazonates (azines). The reaction is atom economic with an easily operational procedure for divergent synthesis of important scaffolds.

Palladium-catalyzed anti-Markovnikov oxidative acetalization of activated olefins with iron(III) sulphate as the reoxidant

This paper discloses the efficient palladium-catalyzed anti-Markovnikov oxidative acetalization of activated terminal olefins with iron(III) sulfate as the reoxidant. This methodology requires mild reaction conditions and shows high regioselectivity toward anti-Markovnikov products and compatibility with a wide range of functional groups. Iron(III) sulphate was the sole reoxidant used in this method. Various olefins like vinylarenes, aryl-allylethers, aryl or benzyl acrylates and homoallylic alcohols all reacted well providing anti-Markovnikov acetals, some of which represent orthogonally functionalized 1,3- and 1,4-dioxygenated compounds.

Synthesis of 5-Vinyl-2-isoxazolines by Palladium-Catalyzed Intramolecular O-Allylation of Ketoximes

An efficient method for the synthesis of 5-vinyl-2-isoxazolines by Pd-catalyzed intramolecular O-allylation of ketoximes has been developed. The reaction involves Pd(0)-catalyzed π-allyl formation via leaving group ionization or Pd(II)-catalyzed allylic C-H activation followed by intramolecular nucleophilic oxime oxygen attack. This methodology has been elaborated to various value-added products by epoxidation, Wacker oxidation, cross-metathesis, hydroboration-oxidation, dihydroxylation, and catalytic hydrogenation.

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 Wacker oxidation: from conventional to modern variants and applications

Recent developments in the well-known Wacker oxidation process from conventional to modern variants and applications to natural products' synthesis are compiled in this review.

A Representative Synthetic Route for C5 Angucycline Glycosides: Studies Directed toward the Total Synthesis of Mayamycin

This study discloses an efficient synthetic route for the regiospecific construction of a C5 glycoside angucycline representative of mayamycin. The key steps are intramolecular aldol condensation and Hauser annulation, and the key precursor for the aldol reaction is accessible through utilization of α-lithiation of a vinyl ether.

Wacker-Type Oxidation Using an Iron Catalyst and Ambient Air: Application to Late-Stage Oxidation of Complex Molecules

A practical and general iron-catalyzed Wacker-type oxidation of olefins to ketones is presented, and it uses ambient air as the sole oxidant. The mild oxidation conditions enable exceptional functional-group tolerance, which has not been demonstrated for any other Wacker-type reaction to date. The inexpensive and nontoxic reagents [iron(II) chloride, polymethylhydrosiloxane, and air] can, therefore, also be employed to oxidize complex natural-product-derived and polyfunctionalized molecules.

Hypervalent Iodine as a Terminal Oxidant in Wacker-Type Oxidation of Terminal Olefins to Methyl Ketones

A mimic of the Wacker process for C═O bond formation in terminal olefins can be initiated by a combination of the Pd(II) and hypervalent iodine reagent, Dess-Martin periodinane to generate methyl ketones. This operationally simple and scalable method offers Markovnikov selectivity, has good functional group compatibility, and is mild and high yielding.

Iron(III) sulfate as terminal oxidant in the synthesis of methyl ketones via Wacker oxidation

An efficient and environmentally benign method using Fe(III) sulfate as a terminal oxidant in the synthesis of methyl ketones from terminal olefins via the Wacker process is developed. The methodology offers high selectivity for a Markonikov product, shows good functional group compatibility, involves mild reaction conditions, and is operationally simple. Fe2(SO4)3 is the sole terminal oxidant in this process. The method holds potential for future applications in organic synthesis.