Selective quantitative N-functionalization of unprotected α-amino acids using NHC-Ir(III) catalyst.

Unnatural amino acids are valuable building blocks with numerous applications. Here, we present a quantitative technique for accessing mono-N-functionalized amino acids directly from unprotected substrates using alcohols as alkylating agents and an NHC-Ir(III) catalyst. We detail specific steps for catalyst preparation and application, as well as for catalyst recycling. The protocol excludes a few amino acids (l-cysteine, l-lysine, and l-arginine) and secondary alcohols. For complete details on the use and execution of this protocol, please refer to Bermejo-López et al. (2022).1.

Iron-Catalyzed Borylation of Propargylic Acetates for the Synthesis of Multisubstituted Allenylboronates.

A novel iron-catalyzed borylation of propargylic acetates leading to allenylboronates has been developed. The method allows the preparation of a variety of di-, tri- and tetrasubstituted allenylboronates at room temperature with good functional group compatibility. Stereochemical studies show that an anti-SN 2' displacement of acetate by boron occurs; this also allows transfer of chirality to yield enantiomerically enriched allenylboronates. The synthetic utility of this protocol was further substantiated by transformations of the obtained allenylboronates including oxidation and propargylation.

Iron-Catalyzed Cross-Coupling of Propargyl Ethers with Grignard Reagents for the Synthesis of Functionalized Allenes and Allenols.

Herein we disclose an iron-catalyzed cross-coupling reaction of propargyl ethers with Grignard reagents. The reaction was demonstrated to be stereospecific and allows for a facile preparation of optically active allenes via efficient chirality transfer. Various tri- and tetrasubstituted fluoroalkyl allenes can be obtained in good to excellent yields. In addition, an iron-catalyzed cross-coupling of Grignard reagents with α-alkynyl oxetanes and tetrahydrofurans is disclosed herein, which constitutes a straightforward approach towards fully substituted ß- or γ-allenols, respectively.

Nonclassical Mechanism in the Cyclodehydration of Diols Catalyzed by a Bifunctional Iridium Complex.

1,4- and 1,5-diols undergo cyclodehydration upon treatment with cationic N-heterocyclic carbene (NHC)-IrIII complexes to give tetrahydrofurans and tetrahydropyrans, respectively. The mechanism was investigated, and a metal-hydride-driven pathway was proposed for all substrates, except for very electron-rich ones. This contrasts with the well-established classical pathways that involve nucleophilic substitution.