Metal -free PhI(OAc)2-oxidized decarboxylation of propiolic acids towards synthesis of α-acetoxy ketones and insights into general decarboxylation with DFT calculations

A metal-free oxidative decarboxylation reaction of propiolic acids mediated by hypervalent iodine(III) reagents is described. This decarboxylative C-O bond-forming reaction used a combination of (diacetoxyiodo)benzene and aromatic, heteroaromatic or aliphatic propiolic acids to give the corresponding α-acetoxy ketones. Preliminary mechanistic studies based on both DFT calculations and high-resolution mass spectroscopy (HRMS) suggested that the reaction proceeded through decarboxylation to form a propargyl iodide intermediate. This reaction provides an attractive alternative to existing methods for the exclusive synthesis of α-acyloxy ketones.

Heck Reaction of 2-Oxyacrylates with Aryl Bromides: A Common Route to Monoaryl Pyruvates and Ortho Ester-Protected Monoaryl Pyruvates

A palladium-catalyzed Heck reaction between 2-oxyacrylates and aryl bromides was developed, where DavePhos was a unique ligand that efficiently promoted the reaction. The products, 2-oxycinnamates, served as excellent precursors, providing synthetically useful monoaryl pyruvates or ortho ester-protected monoaryl pyruvates depending on the nature of the 2-oxy group. The formation of such ortho esters via alkoxide addition is novel, and computational studies identified a plausible mechanism with an oxyallyl zwitterion as the key intermediate.

Alkyl Enol Ethers: Development in Intermolecular Organic Transformation

Alkyl enol ethers (AEE) are versatile synthetic intermediates with a unique reactivity pattern. This review article summarizes the synthesis of AEE as well as its reactivity and how enol ether undergoes intermolecular reactions for various bond formation, leading to the construction of several useful organic molecules. The synthetic applications of alkyl enol ethers towards intermolecular bond-forming reactions include metal-catalyzed reactions, cycloaddition and heterocycle formation as well as rwactions in the field of natural products synthesis. The achievement of these impressive transformations prove the countless synthetic potential of AEE. The main objective of this review is to bring attentiveness among synthetic chemists to show how AEE extensively can be used to react with both electrophiles as well as nucleophiles, thereby behaving as an ambiphilic reactant. We trust that the unique reactivity pattern of alkyl enol ethers and the fundamental mechanistic idea can attract chemists in AEE chemistry. Exclusively, intermolecular reactions of AEE with other functionalized moieties have not been reviewed to the best of our knowledge.

Chemiluminescence-promoted oxidation of alkyl enol ethers by NHPI under mild conditions and in the dark

The hydroperoxidation of alkyl enol ethers using N-hydroxyphthalimide and molecular oxygen occurred in the absence of catalyst, initiator, or light. The reaction proceeds through a radical mechanism that is initiated by N-hydroxyphthalimide-promoted autoxidation of the enol ether substrate. The resulting dioxetane products decompose in a chemiluminescent reaction that allows for photochemical activation of N-hydroxyphthalimide in the absence of other light sources.

Sustainable Hydrogenation of Vinyl Derivatives Using Pd/C Catalysts

The hydrogenation of unsaturated double bonds with molecular hydrogen is an efficient atom-economic approach to the production of a wide range of fine chemicals. In contrast to a number of reducing reagents typically involved in organic synthesis, hydrogenation with H2 is much more sustainable since it does not produce wastes (i.e., reducing reagent residues). However, its full sustainable potential may be achieved only in the case of easily separable catalysts and high reaction selectivity. In this work, various Pd/C catalysts were used for the liquid-phase hydrogenation of O-, S-, and N-vinyl derivatives with molecular hydrogen under mild reaction conditions (room temperature, pressure of 1 MPa). Complete conversion and high hydrogenation selectivity (>99%) were achieved by adjusting the type of Pd/C catalyst. Thus, the proposed procedure can be used as a sustainable method for vinyl group transformation by hydrogenation reactions. The discovery of the stability of active vinyl functional groups conjugated with heteroatoms (O, S, and N) under hydrogenation conditions over Pd/C catalysts opens the way for many useful transformations.