A Total Synthesis of Paeoveitol

A four-step total synthesis of paeoveitol (<b>1</b>), a recently disclosed norditerpene natural product from <i>Paeonia vetchii</i>, is reported. This highly concise synthetic route was guided by biosynthetic considerations and enabled by an unusual intermolecular <i>ortho</i>-quinone methide [4 + 2]-cycloaddition reaction, which proceeded with excellent regio- and diastereoselectivity. Density functional theory (DFT) calculations point to a crucial intermolecular hydrogen bond and π–π stacking interaction that govern selectivity in this process

Ar-BINMOL–Derived Salan–Cu(II) Complex–Catalyzed Silyl-Reformatsky Reaction of Aromatic Aldehydes

<div><p></p><p>In this work, we have developed a facile protocol with salan–Cu system for the facile and selective synthesis of β-hydroxyesters via silyl-Reformatsky reaction with α-silylester and aldehydes. The screening and optimization of reaction conditions led to the determination of a practical and efficient procedure in which the salan–Cu exhibited promising catalytic activity in dimethylsulfoxide, in which the silyl-Reformatsky reaction of aromatic aldehydes with α-trimethylsilylmethylacetate gave the corresponding β-hydroxyester derivatives in excellent yields (up to 98%) under fluoride-free reaction conditions.</p> </div

Aromatic-Amide-Derived Nonbiaryl Atropisomer as Highly Efficient Ligand for Asymmetric Silver-Catalyzed [3 + 2] Cycloaddition

In this work, we have successfully determined that the aromatic amide-derived nonbiaryl atropisomer/silver complex (silver-Xing-Phos) is an effective catalyst system for the solvent-dependent <i>exo</i>-selective cycloaddition of glycine aldimino esters with chalcones or less-reactive methyl cinnamates to give the corresponding chalcone- or cinnamate-derived pyrrolidines with multiple stereogenic centers in good yields and high diastereoselectivities as well as excellent enantioselectivities. Remarkably, it is the first example of highly enantioselective silver-catalyzed [3 + 2] cycloaddition of methyl cinnamates with glycine aldimino esters

Cyclotriphophazene-Centered Six-Arm Eugenol-Linked Low-Dielectric Materials with High Thermostability and Transparency

Two silicon-containing eugenol-based benzocyclobutene monomers were prepared by a simple solvent-free hydrosilylation reaction. After heat treatment, a series of materials were obtained by a free radical addition reaction, [4 + 4] cycloaddition, or [4 + 2] Diels–Alder cycloaddition. All polymers displayed high thermostability with a 5% weight loss temperature (T5d) of over 410 °C and a glass transition temperature (Tg) of up to 216 °C as well as a good transmittance of 90% varying from 500 to 800 nm. In particular, all polymers also exhibited good hydrophobicity with contact angles exceeding 100° and water absorption as low as 8‰ after immersing in boiling water for 72 h. It should be noted that P3 showed excellent dielectric properties with a dielectric constant (Dk) of 2.48 and a dielectric loss (Df) of 6.38 × 10–3 at a high frequency of 2 GHz as well as good flame retardancy due to the high content of cyclotriphophazene compared with those of P1, P2, and previously reported biobased materials. The above advantages indicate that eugenol-based low-dielectric materials have great potential for application in encapsulation resins in the field of microelectronics

Rhodium-Catalyzed Hydrolytic Cleavage of the Silicon–Carbon Bond of Silacyclobutanes to Access Silanols

Herein, we report the first rhodium-catalyzed hydrolytic cleavage of the silicon–carbon bond in silacyclobutanes using water as the reactant. A series of silacyclobutanes could be employed in this reaction in the presence of the Rh/BINAP complex, resulting in the corresponding silanols in good yields. Additionally, a chiral 1,1,4,4-tetraaryl-2,3-O-isopropylidene-l-threitol-derived phosphoramidite ligand could be used in this reaction to yield Si-stereogenic silanol with promising enantioselectivity

Privilege Ynone Synthesis via Palladium-Catalyzed Alkynylation of “Super-Active Esters”

A neat palladium-catalyzed alkynylation reaction was developed with “super-active ester” as the carbonyl electrophile, which provides a clean and efficient synthetic protocol for a broad array of ynone compounds under CO-, Cu-, ligand-, and base-free conditions. The superior activity of triazine ester was rationalized by the strong electron-withdrawing ability and the unique affinity of triazine on palladium. A mechanistic experiment clearly demonstrated that the N–Pd coordination of triazine plays a crucial role for the highly efficient C–O activation

Ligand-Controlled Inversion of Diastereo- and Enantioselectivity in Silver-Catalyzed Azomethine Ylide–Imine Cycloaddition of Glycine Aldimino Esters with Imines

A highly diastereo- and enantioselective silver-catalyzed azomethine ylide–imine (AYI) cycloaddition reaction of glycine aldimino esters with imines was developed in which the Xing-Phos-controlled <i>syn</i>-selective or DTBM-Segphos-induced <i>anti</i>-selective AYI cycloaddition reaction could be applied to the synthesis of a variety of stereodivergent 1-alkyl-2,5-substituted imidazolidines with high yields and excellent enantioselectivities (up to 99% ee) as well as good diastereoselectivities (up to 99:1 dr) under mild reaction conditions

Investigation of the Mitsunobu Reaction of BINOL and Cinchona Alkaloids: Inversion or Retention of Configuration?

<div><p></p><p>An efficient approach toward the construction of multistereogenic binaphthol (BINOL)–derived alkaloids with C₂-axial and sp³ central chirality has been accomplished. The reaction of BINOL and cinchona alkaloids was occurred smoothly under the Mitsunobu conditions, which led to the synthesis of a new family of complicated functional molecules based on chiral BINOL and cinchona alkaloids. In addition, on the basis of the experimental results, we provided a possible explanation for the intramolecular tertiary amine-induced retention of configuration at C9 of cinchona alkaloids while the inversion of configuration was observed with general alcohols under classic Mitsunobu conditions.</p> </div

Asymmetric Synthesis of Glutamic Acid Derivatives by Silver-Catalyzed Conjugate Addition–Elimination Reactions

The enantioselective construction of a family of chiral glycine-derived aldimino esters is described. The asymmetric tandem conjugate addition–elimination procedure is characterized by its exceptional mild reaction conditions and features with an exquisite enantioselectivity profile using commercially available silver/DTBM-SegPhos catalyst, allowing for the facile preparation of a variety of substituted and chiral glutamic acid derivatives (up to 99% ee) bearing Schiff base in a straightforward manner

3‑Alkyl-2-pyridyl Directing Group-Enabled C2 Selective C–H Silylation of Indoles and Pyrroles via an Iridium Catalyst

An iridium-catalyzed, directing group-enabled site selective intra- and intermolecular silylation of indoles and pyrroles with hydrosilanes has been developed under ligand-free conditions. Fine-tuning of the removable 3-alkyl-2-pyridyl directing group was found to be crucial for achieving high yields for C2-silylated indole and pyrrole products. Moreover, the scalability was demonstrated, and further transformations of the silylation products were achieved