Zinc-Mediated Chain Extension Reaction of 1,3-Diketones to 1,4-Diketones and Diastereoselective Synthesis of trans-1,2-Disubstituted Cyclopropanols

Pd-catalyzed CO-free double carbonylation for the synthesis of 1,4-ketoesters with Mo(CO)6 as the carbonyl source

An unprecedented Pd-catalyzed CO-free double carbonylation using Mo(CO)6 as a safe carbonyl source for the efficient synthesis of 1,4-ketoesters in an atom- and step-economic manner has been developed. The current method features operational safety, a wide substrate range, good functional group compatibility and easy scale-up. The application of carbonylation using a safe carbonyl source for the synthesis of biologically and synthetically useful carbonyl-containing molecules is underway in our lab.

Lithium Bromide-Promoted Formal C(sp3)-H Bond Insertion Reactions of β-Carbonyl Esters with Sulfoxonium Ylides to Synthesize 1,4-Dicarbonyl Compounds

A LiBr-promoted formal C(sp3)-H bond insertion reaction between β-carbonyl esters and sulfoxonium ylides is established. This practical reaction has a wide range of substrate scope for both β-carbonyl esters and sulfoxonium ylides to give a variety of 1,4-dicarbonyl compounds with 43-94% yields. The reaction features transition-metal-free reaction conditions and exclusive C-alkylation chemselectivity. The use of bench-stable sulfoxonium ylides overcomes previous methods that require transition metal as catalysts and unstable diazo compounds or toxic haloketones as alkylation reagents.

Copper-Catalyzed Three-Component Reactions of α-Ketoaldehyde, 1,3-Dicarbonyl Compound, and Organic Boronic Acid in Water: A Route to 1,4-Diketones

A novel three-component reaction of α-ketoaldehydes, 1,3-dicarbonyl compounds, and organic boronic acids catalyzed by CuO in water has been developed to give a wide range of products containing 1,3/1,4-diketones. The method has some advantages such as the use of readily available starting materials, wide substrate scopes, excellent yields, gram-scale synthesis, and mild reaction conditions.

Photochemical Synthesis of 1,4-Dicarbonyl Bifluorene Compounds via Oxidative Radical Coupling Using TEMPO as the Oxygen Atom Donor

A visible-light-induced metal-free synthesis of 1,4-dicarbonyl compounds from alkyne-containing aryl iodides via photochemical C-I bond cleavage, intramolecular cyclization, oxidation, and intermolecular radical coupling sequence is reported. TEMPO was employed as the oxygen atom donor in this transformation. This protocol provided a new strategy for the synthesis of 1,4-dicarbonyl bifluorene compounds.

Synthesis of a Novel 1,4-Dicarbonyl Scaffold – Ethyl 3-Formyl-4,5-dihydrofuran-2-carboxylate – and Its Application to the Synthesis of Pyridazines

The 1,4-dicarbonyl scaffold ethyl 3-formyl-4,5-dihydrofuran-2-carboxylate was obtained through the rearrangement of the parent ethyl 2-(4,5-dihydrofuran-3-yl)-2-oxoacetate and applied to the synthesis of a series of 7-alkoxy-2,3-dihydrofuro[2,3-d]pyridazines. Twelve pyridazines­ were obtained in yields of up to 70%.

Developments in the construction of cyclopropanols

The ring-opening of cyclopropanols is one of the most active areas of research and it has been well documented in recent years owing to subsequent coupling with various partners, thus providing the facile syntheses of a large number of multifunctional compounds that may otherwise be difficult to access. Evidently, the useful cascade reaction requires easy access to diversely functionalized cyclopropanol substrates. However, developments in the construction of cyclopropanols have not received adequate attention. Herein, recent reports on the formation of cyclopropanols are summarized, and the highly stereoselective production of new promising substrates for the cyclopropanol ring-opening/cross-coupling reactions are introduced and improved syntheses of known cyclopropanols are depicted. This review may facilitate more interesting applications of the cyclopropanol ring-opening/coupling reaction in the synthesis of pharmaceutical compounds, natural products, and structurally more diversified organic synthetic intermediates.

1,4-Refunctionalization of β-diketones to γ-keto nitriles via C–C single bond cleavage

The 1,4-refunctionalization of β-diketones to γ-keto nitriles was realized via an Fe-catalyzed cascade radical process.

A novel class of tunable cyclopropanation reagents (RXZnCH2Y) and their synthetic applications

The Simmons-Smith cyclopropanation is a widely used method to synthesize cyclopropanes from alkenes using methylene iodide and a zinc reagent. A novel class of organozinc species, RXZnCH(2)Y, has been found to efficiently cyclopropanate alkenes, including traditionally unreactive unfunctionalized alkenes. The reactivity and selectivity of this class of organozinc reagents can be regulated by tuning the electronic and/or steric nature of the RX group attached to Zn. During recent years, this class of organozinc reagent has been widely used in organic synthesis as a reagent for cyclopropanation and other useful synthetic transformations. Catalytic, asymmetric versions of this reaction have been developed providing high enantiomeric excess for unfunctionalized olefins.

A mechanistic investigation into the zinc carbenoid-mediated homologation reaction by DFT methods: is a classical donor-acceptor cyclopropane intermediate involved?

An extensive density functional theory (DFT, M05-2X) investigation has been performed on the zinc carbenoid-mediated homologation reaction of β-keto esters. The mechanistic existence of a classical donor-acceptor cyclopropane intermediate was probed to test the traditional school of thought regarding these systems. Calculations of the carbenoid insertion step, following enolate formation, unmasked two possible pathways. Pathway B was shown to explain the proposed, but spectroscopically unobservable donor-acceptor cyclopropane intermediate, while the second (pathway A) reveals an alternative to the classical intermediate in that a cyclopropane transition state leads to product.

Benzoyl radicals from (hetero)aromatic aldehydes. Decatungstate photocatalyzed synthesis of substituted aromatic ketones

Benzoyl radicals are generated directly from (hetero)aromatic aldehydes upon tetrabutylammonium decatungstate ((n-Bu(4)N)(4)W(10)O(32)), TBADT) photocatalysis under mild conditions. In the presence of alpha,beta-unsaturated esters, ketones and nitriles radical conjugate addition ensues and gives the corresponding beta-functionalized aryl alkyl ketones in moderate to good yields (stereoselectively in the case of 3-methylene-2-norbornanone). Due to the mild reaction conditions the presence of various functional groups on the aromatic ring is tolerated (e.g. methyl, methoxy, chloro). The method can be applied to hetero-aromatic aldehydes whether electron-rich (e.g. thiophene-2-carbaldehyde) or electron-poor (e.g. pyridine-3-carbaldehyde).

Zinc-Mediated C−C Bond Sigmatropic Rearrangement: A New and Efficient Methodology for the Synthesis of β-Diketones

A new and efficient methodology has been developed for the synthesis of beta-diketones from aromatic alpha-bromo ketones in the presence of Furukawa reagent under mild conditions. The present transformation is proposed to proceed via a Reformatsky-type reaction of alpha-bromo ketones, followed by C-C bond sigmatropic rearrangement of the aldolate intermediate to give beta-diketones in moderate to good isolated yields, while aliphatic alpha-bromomethyl ketones resulted in the formation of 2,4-disubstituted furans or cis-1,2-disubstituted cyclopropanols in moderate yields. The scope of this process was investigated, and a tentative mechanism was proposed.