Enantioselective Synthesis of α-Hydroxy Allyl Ketones via BINAP-CuH-Catalyzed Hydroacylation

Catalytic hydrocupration of unsaturated carbon-carbon bonds to generate organometallic nucleophiles has recently become an attractive alternative to conventional stoichiometric reagents in the stereoselective synthesis. Herein, we have developed an efficient and economical method to synthesize enantiopure α-hydroxy allyl ketones via a copper hydride (CuH)-catalyzed hydroacylation of alkoxyallenes, a significant advancement given the scarcity of reports on such scaffolds in the literature. DFT calculations reveal that this reaction proceeds through the nucleophilic attack of a kinetically favourable Z-selective allyl-copper intermediate on acid anhydrides via a six-membered chair-like transition state, stabilized by strongly attractive non-covalent interactions that ultimately leads to high level of enantioselectivities using the simple BINAP ligand. This method successfully overcomes the challenges of over-reduction of carbonyl functionality in the presence of CuH-complex, olefin isomerization and the presence of a highly enolizable α-stereocenter, which can lead to erosion in enantioselectivities, making our strategy highly desirable. The reaction exhibits a wide range of substrate scope including symmetrical as well as carbonic anhydrides with both aromatic, and aliphatic substitutions. In addition, α-substituted acid anhydrides provide exclusive syn-selective α,α'-disubstituted allyl ketones in excellent enantiomeric ratios, where the nucleophilic allylation occurs on one of the carbonyls containing the matched α-stereocenter, confirmed with mechanistic studies.

Phosphinothio(seleno)ation of alkynes/olefins and application on the late-stage functionalization of natural products

Non-metallic catalysis has been known as a remarkable development strategy for hydrofunctionalization of unsaturated hydrocarbons. Herein, we report a unique chemically active method of BF3·OEt2 promoted multi-component, highly regioselective, and chemoselective hydrothio(seleo)phosphonylation of unsaturated hydrocarbons, which exhibits high yield and good substrate universality. The reaction mechanism was further elucidated to be Markovnikov addition by controlling experiments, 31P and 19F NMR spectra tracking experiments, X-ray diffraction analysis, and DFT calculations. Furthermore, the gram-scale attempt and the application of the reaction on the derivatization of natural products have been successfully conducted, leading to the discovery of 3as with potential anti-Parkinson's disease (PD) activities at 1 μM. This streamlined and efficient methodology has established a new platform for non-metallic Lewis acids-promoted hydrofunctionalization of unsaturated hydrocarbons and its application on new drug research.

Organic Photoredox-Catalyzed Hydrosilylation of Vinylboronic Esters for the Synthesis of Geminal and Vicinal Borosilanes

Geminal and vicinal borosilanes have unique applications in functional materials and synthetic transformations. Herein, a convenient method for the synthesis of geminal and vicinal borosilanes is developed via photoredox metal-free hydrosilylation of vinylboronic esters. This strategy features the advantages of high atom economy, environmental friendliness, and excellent functional group compatibility. The mechanism studies reveal that the catalytic reaction goes through photoredox HAT catalysis and a radical addition pathway.

Copper catalysed protoboration of allenyl-Bdans: efficient synthesis of β-boryl allyl-Bdans

A novel strategy for the selective synthesis of β-boryl allyl-Bdan derivatives by employing Cu-catalyzed protoboration of allenyl-Bdan derivatives was developed.

Regio-divergent hydroboration of terminal allenes controlled by nickel and cobalt catalysts

A highly efficient regioselective method for allene hydroboration has been developed, with the regioselectivity governed primarily by the appropriate choice of the metal.

Catalytic enantioselective allene-anhydride approach to β,γ-unsaturated enones bearing an α-all-carbon-quarternary center

A protocol of highly regio- and enantioselective copper-catalyzed hydroacylation of the non-terminal C[double bond, length as m-dash]C bond in 1,1-disubstituted terminal allenes with anhydrides has been developed. Both aromatic and aliphatic carboxylic anhydrides are applicable to the efficient construction of all carbon quarternary centers connected with a versatile C[double bond, length as m-dash]C bond and a useful ketone functionality. The synthetic potentials of the enantioenriched products have also been demonstrated. Density functional theory (DFT) calculations were performed to explain the steric outcome of the products: the hydroacylation proceeds through a six-membered transition state and the ligand-substrate steric interactions account for the observed enantioselectivity although the chiral ligand is far away from the to-be-genetated chiral center.

An Efficient Approach to Regio- and Stereodefined Fully-Substituted Alkenylsilanes by Pd-Catalyzed Allenic C(sp3 )-H Oxidation

A highly efficient palladium-catalyzed functionalization of allenylsilanes to give regio- and stereodefined fully-substituted alkenylsilanes has been developed. This oxidative coupling reaction showed good functional group compatibility with exclusive regio- and stereoselectivity. The pending olefin on the silyl group was shown to be an indispensable element for the initial allenic C(sp³ )-H bond cleavage, and performs as the directing group to control the overall selectivity. The addition of substoichiometric amounts of Et₃ N was found to increase the reaction rate leading to a higher reaction yield. The reaction can be easily scaled up and applied for the late-stage functionalization of natural products and pharmaceutical compounds, including amino acids and steroid derivatives. The newly introduced functional groups include aryl, alkynyl, and boryl groups. The highly strained four-membered ring, silacyclobutene was obtained when B₂ pin₂ was employed as the coupling partner. Mechanistic studies, including kinetic isotope effects, showed that the allenic C(sp³ )-H bond cleavage is the rate-limiting step.

Iron-mediated highly diastereoselective allylation of carbonyl compounds with cyclic allylic halides

An efficient iron-mediated highly diastereoselective allylation reaction of carbonyl compounds with cyclic allylic halides using a catalytic amount of bismuth(iii) chloride is reported.

Metal-catalyzed regiodivergent organic reactions

This review discusses metal-catalysed regiodivergent additions, allylic substitutions, CH-activation, cross-couplings and intra- or intermolecular cyclisations.

B(MIDA)-Containing Diborons

Unsymmetrical B(MIDA)-containing diborons of potential synthetic utility were found to be synthesized from the readily available (neop)B-B(neop) and (HO)₂B-B(OH)₂, and the procedure was extended to the generation of symmetrical (MIDA)B-B(MIDA). NMR and X-ray crystal structure studies revealed that B(MIDA) units of all of the diborons obtained in this study were in rigid tetrahedral environment.

Selective syntheses of diversely substituted 2-hydroxy-4′-hydroxybenzophenones through [4 + 2] or [3 + 3] annulation of penta-3,4-dien-2-ones with 3-formylchromones

A selective synthesis of 2-hydroxy-4′-hydroxybenzophenones or their 3′-acylated counterparts via the cascade reactions of 3-formylchromones with diversely substituted penta-3,4-dien-2-ones is presented.