Sequential Palladium-Catalyzed Allylic Alkylation/retro-Dieckmann Fragmentation Strategy for the Synthesis of α-Substituted Acrylonitriles

Vitrimer-like elastomers with rapid stress-relaxation by high-speed carboxy exchange through conjugate substitution reaction

We report vitrimer-like elastomers that exhibit significantly fast stress relaxation using carboxy exchange via the conjugate substitution reaction of α-(acyloxymethyl) acrylate skeletons. This network design is inspired by a small-molecule model that shows the carboxy exchange reaction even at ambient temperature in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO). The acrylate and acrylic acid copolymers are cross-linked using bis[α-(bromomethyl)acrylates] and doped with 10 wt% DABCO, exhibiting processability to obtain a transparent film by hot pressing. The high-speed bond exchange in the network, validated by stress-relaxation tests, allows quick molding with household iron. In addition, the material is applied as an adhesion sheet for plastic and metal substrates. Because dynamic cross-linking with the proposed bond exchange mechanism can be implemented for any polymer bearing carboxyl pendants, our approach can be applied to versatile backbones, which must thus be meaningful in the practical sense.

Regioselective Coupling of Different Conjugate Esters by Magnesium Metal Reduction: A Route to Unsymmetrical Adipic Acid Esters

A novel tactic to synthesize unsymmetrical 3-aryladipic acid esters has been developed via magnesium-promoted reductive coupling of ethyl cinnamates with methyl acrylate. In the present methodology, 3-aryladipic acid derivatives were prepared with good functional group tolerance and a wide substrate scope under very mild reaction conditions in good yields. The application of this reaction to dienic acid esters led to the successful control of the reaction to give 5-aryl-oct-3-enedioic acid esters with high regioselectivity.

Synthesis of Chiral 2,3-Dihydrofurans via One-Pot Pd-Catalyzed Asymmetric Allylic Cycloaddition and a Retro-Dieckmann Fragmentation Cascade

An efficient method for the enantioselective synthesis of 2,3-dihydrofurans bearing a quaternary stereocenter has been developed via Pd-catalyzed asymmetric allylic cycloaddition and a retro-Dieckmann Fragmentation cascade. The asymmetric allylic cycloaddition of vinylethylene carbonates with 3-cyanochromone followed by base-assisted retro-Dieckmann fragmentation proceeded smoothly via a one-pot process to produce chiral 3,4-disubstituted 2,3-dihydrofurans in high yields with excellent enantioselectivities.

Iridium-Catalyzed Enantioselective Formal α-Allylic Alkylation of Acrylonitrile

A highly enantioselective formal α-allylic alkylation of acrylonitrile is developed using 4-cyano-3-oxotetrahydrothiophene (c-THT) as a safe and easy-to-handle surrogate of acrylonitrile. This two-step process consists of an Ir(I)/(P,olefin)-catalyzed branched-selective allylic alkylation using easily accessible branched rac-allylic alcohols as the allylic electrophile followed by retro-Dieckmann/retro-Michael fragmentation and is shown to be applicable for the enantioselective synthesis of α-allylic acrylates as well as α-allylic acrolein.

Enantioselective Synthesis of Skipped Dienes via Iridium-Catalyzed Allylic Alkylation of Phosphonates

An enantioselective synthesis of skipped dienes has been developed based on an iridium-catalyzed allylic alkylation of phosphonates and Horner-Wadsworth-Emmons olefination. This two-step protocol uses easily accessible substrates and delivers C2-substituted skipped dienes bearing a C3 stereogenic center, generally with outstanding enantioselectivities (up to 99.5:0.5 er). This is the first catalytic enantioselective allylic alkylation of phosphonates, and the overall process represents a formal enantioselective α-C(sp²)-H allylic alkylation of α,β-unsaturated carbonyls and acrylonitrile.

Hypersampones A-C, Three Nor-Polycyclic Polyprenylated Acylphloroglucinols with Lipid-Lowering Activity from Hypericum sampsonii

Hypersampones A-C (1-3), three unprecedented nor-polycyclic polyprenylated acylphloroglucinols (PPAPs), were isolated from Hypericum sampsonii. These compounds represent the first nor-PPAPs with an unexpected tetracyclic 6/5/5/6 ring system. Their structures were assigned through the analysis of detailed spectroscopic data, X-ray crystallography, and electronic circular dichroism calculations. Compound 1 significantly inhibited the accumulation of lipid in an oleic acid-treated HepG2 cell model by suppressing the protein expression of FAS and ACACA at 5 μM.

Umpolung carbonyls enable direct allylation and olefination of carbohydrates

Mother Nature has its own arts to build a vast number of carbohydrates; however, there is still a lack of tools for selective functionalization of native carbohydrates through C─C bond formation. Such a long-standing challenge for the synthetic community lies into the intrinsic problems related to the innate properties of carbohydrates, e.g., the ease to oligomerization or polymerization, the difficulty of chemoselectivity control in the presence of multiple hydroxyl groups, the great challenge to retain the multiple chiral centers during the transformation, etc. Here, by applying an umpolung strategy of carbohydrate carbonyls, we report a direct deoxygenative allylation and olefination of carbohydrates to tackle the abovementioned issues. The reaction is compatible with a wide range of natural carbohydrates, providing a direct synthetic method to use carbohydrates as multiple C-centered chiral synthons to achieve C─C bond cross-coupling reactions. Furthermore, the synthetic applicability is demonstrated by late-stage modifications of natural products and pharmaceutical derivatives.

4-Cyano-3-oxotetrahydrothiophene (c-THT): An Ideal Acrylonitrile Anion Equivalent

4-Cyano-3-oxotetrahydrothiophene (c-THT) has much more to offer than just a platform to various heterocyclic scaffolds. This solid, bench-stable and commercially available reagent can be readily transformed into thioglycolic acid and acrylonitrile upon simple addition of a hydroxide anion. This interesting feature enables its use as a particularly versatile acrylonitrile anion surrogate.

O-Allylated Pudovik and Passerini Adducts as Versatile Scaffolds for Product Diversification

The palladium-catalyzed O-allylation of α-hydroxyphosphonates and α-hydroxyamides obtained from Pudovik and Passerini multicomponent reactions has allowed interesting and highly straightforward access to a variety of building blocks for product diversification. These post-functionalizations include a selective base- or ruthenium hydride-mediated isomerization/Claisen rearrangement cascade and a ring-closing metathesis that allows access to a variety of diversely functionalized phosphono-oxaheterocycles.

Direct Access to Highly Enantioenriched α-Branched Acrylonitriles through a One-Pot Sequential Asymmetric Michael Addition/Retro-Dieckmann/Retro-Michael Fragmentation Cascade

A highly enantioselective synthesis of α-branched acrylonitriles is reported featuring a one-pot sequential asymmetric Michael addition/retro-Dieckmann/retro-Michael fragmentation cascade. The method, which relies on a solid, bench-stable, and commercially available acrylonitrile surrogate, is practical, scalable, and highly versatile and provides a direct access to a wide range of enantioenriched nitrile-containing building blocks. Most importantly, the method offers a new tool to incorporate an acrylonitrile moiety in an asymmetric fashion.