Synlett

The synthesis of some new functionalized azaheterocyclic β-amino esters with multiple stereocenters has been achieved from readily available unsaturated bicyclic β-amino acids by a stereocontrolled synthetic protocol involving N-allylation/propargylation, ring-opening metathesis, and selective ring closure with chemodifferentiation through ring-closing metathesis (RCM). The RCM transformation was investigated under various experimental conditions to analyze the scope of the catalyst, yield, conversion, and substrate effect. The structure of the starting (oxa)norbornene β-amino acids predetermined the structure of the new azaheterocyclic derivatives; the synthetic procedure proceeded with conservation of the configuration of the stereogenic centers.

The asymmetric synthesis of the key skeleton of phosphoeleganin has been achieved for the first time by using a convergent approach. The salient features of this synthesis include amidation to install a glycine amide at the C-1 position, Wittig olefination to access the C5–C6 bond, Julia–Kocienski olefinations to prepare the C9–C10 and C13–C14 bonds, and a Takai olefination and a Sonogashira coupling to construct the C17–C18 and C18–C19 bonds, respectively. The route disclosed is highly modular, which will permit the synthesis of various analogues, useful for structure–activity relationship studies on phosphoeleganins.

We report an amino acid salt-catalyzed direct desymmetrization of 3-substituted cyclobutanones through a direct aldol reaction under mild reaction conditions. The developed method provides an array of highly functionalized cyclobutanones bearing three contiguous stereogenic centers in high yields and stereoselectivities with varied functional-group compatibility. Furthermore, the obtained adducts can be smoothly converted into polyfunctional 1,4-butyrolactones with maintained enantioselectivity.

Herein, a chemoselective protocol for the facile and efficient synthesis of substituted benzo[c]chromen-6-ones is presented. The reaction took place under green and mild conditions with group-assisted purification (GAP) by using inexpensive and readily available precursors.

SNS-based ruthenium pincer catalysts were applied in a Guerbet condensation reaction of primary alcohols to give β-alkylated dimeric alcohols in good yields. The ability of these complexes to convert ethanol into butanol was also investigated. The work was then extended toward the C-alkylation of secondary alcohols with primary alcohols to give α-alkylated ketones. Several control experiments showed the involvement of borrowing hydrogen in the protocol.

Chiral ligands play an essential role in transition-metal-catalyzed enantioselective transformations, in which chiral oxazoline-based scaffolds are the privileged chiral ligand. Nevertheless, 8-quinolinyl oxazoline (8-Quinox) ligands are underexplored in transition-metal-catalyzed asymmetric transformations since their development in 1998. Herein, we report an 8-Quinox ligand promoted Ni-catalyzed enantioselective reductive carbamoyl-alkylation of carbamoyl chloride tethered styrene with unactivated alkyl iodide, providing an expedient access to valuable enantioenriched oxindoles in good results.

A five-step route to a ring-contracted analogue of the oxicam derivative propoxicam from thiosalicylic acid, sarcosine and N,N-dimethyl-1,3-propanediamine is described. The route has as key steps the base-promoted cross-Claisen coupling of protected sarcosine and thiosalicylic acid derivatives, the installation of a β-ketoamide moiety and a final Hg(II)-induced cyclization that creates the C–S bond of the benzothiophen-3-one core.

Olefin metathesis polymerization has commanded great attention as a versatile method for preparing macromolecular materials with advanced architectures and functions in academia and industry. This Account summarizes our endeavors directed towards the preparation of various functional polymers by using olefin metathesis polymerization strategies in particular acyclic diene metathesis (ADMET) polymerization and ring-opening metathesis polymerization (ROMP), during the last ten years. In addition, the merits and limitations of ADMET polymerization and ROMP techniques are also demonstrated and compared. Notably, this Account highlights our recently developed sequence-controlled ROMP strategy for production of precision polymers in a regio-/stereoselective manner, the rollercoaster journey for the evolution of a macrobicyclic olefin system containing a sacrificial silyloxide bridge is described in detail.1 Introduction2 Olefin Metathesis Step-Growth Polymerization Approaches3 Olefin Metathesis Chain-Growth Polymerization Approaches4 ROMP of Cleavable Bridged Macrobicyclic Olefins5 Conclusion

A novel photoinduced strategy has been developed for the C–H amidation of aromatics and heteroaromatics by using benzamide radicals with free NH groups generated from N-amidopyridinium salts under visible-light irradiation. The new mode of activation of N-amidopyridinium salts proceeds efficiently under mild conditions to give various benzamide derivatives with free NH groups. In addition, oxazoline analogues, synthesized by the reaction with styrene, demonstrate a substantial range of prospective applications for this versatile protocol.

Synlett 2022; 33: V-DOI: 10.1055/s-0041-1738659Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, GermanyArticle in Thieme eJournals:Table of contents