Asymmetric Michael reaction of iminoglycinate 4 to α,β-unsaturated esters had been developed with >98:<2 diastereoselectivity. A reverse of diastereoselectivity for Michael reaction could be achieved by the replacement of lithium enolate with magnesium enolate. This methodology was applied to the total syntheses of (+)-α-allokainic acid 1 and (-)-2- epi-α-allokainic acid 6 each in 11 synthetic steps starting from 4 in 17.8 and 18.0% yields, respectively.

A simple Ni(cod)2 and carbene mediated strategy facilitates the efficient catalytic cross‐coupling of methoxyarenes with a variety of organoboron reagents. Directing groups facilitate the activation of inert C−O bonds in under‐utilized aryl methyl ethers enabling their adaptation for C−C cross‐coupling reactions as less toxic surrogates to the ubiquitous haloarenes. The method reported enables C−C cross‐coupling with readily available and economical arylboronic acid reagents, which is unprecedented, and compares well with other organoboron reagents with similarly high reactivity. Extension to directing group assisted chemo‐selective C−O bond cleavage, and further application towards the synthesis of novel bifunctionalized biaryls is reported. Key to the success of this protocol is the use of directing groups proximal to the reaction center to facilitate the activation of the inert C−OMe bond.

Dicarbon is a reactive carbon allotrope that naturally exists only in the high-temperature medium of stellar space. We report the successful preparation of a series of bottleable phosphine-stabilized dicarbon (PDC) molecules. We explore the use of these molecules as a new complementary class of carbenelike ligands featuring strong σ-donor (>NHCs and CAAcs) but weak π-acceptor properties. Steric map analysis of PDC based on Cavallo's SambVca program reveals comparable steric volume bulk of 32.5%, similar to the conventional IMes carbene. However, our PDCs exhibit dynamic steric flexibility modulated by the nature of the metal complexes and catalytic reaction environment. We demonstrate the catalytic utility of the PDC framework by its successful implementation for Suzuki−Miyaura cross-coupling and the reductive coupling reaction of an aldehyde and alkyne. Detailed investigations of the reductive coupling reaction reveal an important secondary interaction between PDC and metal complexes, which plays a critical role in the catalytic system.

No abstract

We report the preparation and structural characterization of the first known pincer carbodicarbene (CDC) supported ruthenium complexes. The singlecrystal X-ray diffraction experiment indicated that tridentate bis(pyridyl)-CDC free ligand is coordinated to the six-coordinated ruthenium (II) in meridional conformation with each of two chlorides trans to the carbone carbon and phosphine. The pincer effect of new ligand bis(pyridyl)-CDC has shortened the Ru-carbodicarbene bond length in comparison to monodentate CDC. The catalytic activity of the new CDC complexes was tested in hydrogen transfer reaction, revealing the efficient activity of CDC-supported Ru complexes in catalytic transfer hydrogenation of ketone using 2-propanol as hydrogen source.