General stereoretentive preparation of chiral secondary mixed alkylmagnesium reagents and their use for enantioselective electrophilic aminations

A general preparation of enantiomerically and diastereomerically enriched secondary alkylmagnesium reagents was reported as well as their use for performing highly stereoselective transition-metal free electrophilic aminations leading to α-chiral amines in up to 97% ee. Thus, the reaction of t-BuLi (2.2 equiv.) with a mixture of chiral secondary alkyl iodides and the commercially available magnesium reagent Me₃SiCH₂MgCl in a 2 : 1 mixture of pentane and diethyl ether at up to −50 °C provided optically enriched secondary mixed alkylmagnesium species of the type alkyl(Me)CHMgCH₂SiMe₃ with high retention of configuration (up to 99% ee). The resulting enantiomerically enriched dialkylmagnesium reagents were trapped with electrophiles such as non-enolizable ketones, aldehydes, acid chlorides, isocyanates, chlorophosphines and O-benzoyl hydroxylamines providing α-chiral tertiary alcohols, ketones, amides, phosphines and tertiary amines in up to 89% yield (over three reaction steps) and up to 99% ee.

We report a general method for the preparation of enantiomerically enriched secondary alkylmagnesium reagents, which undergo highly stereoselective transition-metal free electrophilic aminations, leading to α-chiral amines in up to 97% ee.     

Mussel‐Inspired Materials: Self‐Healing through Coordination Chemistry

Improved understanding of the underwater attachment strategy of the blue mussels and other marine organisms has inspired researchers to find new routes to advanced materials. Mussels use polyphenols, such as the catechol‐containing amino acid 3,4‐dihydroxyphenylalanine (DOPA), to attach to surfaces. Catechols and their analogues can undergo both oxidative covalent cross‐linking under alkaline conditions and take part in coordination chemistry. The former has resulted in the widespread use of polydopamine and related materials. The latter is emerging as a tool to make self‐healing materials due to the reversible nature of coordination bonds. We review how mussel‐inspired materials have been made with a focus on the less developed use of metal coordination and illustrate how this chemistry can be widely to make self‐healing materials.     

Synthesis and Molecular Structure of 99Tc Corroles

The first ⁹⁹Tc corroles have been synthesized and fully characterized. A single‐crystal X‐ray structure of a ⁹⁹TcO triarylcorrole revealed nearly identical geometry parameters as the corresponding ReO structure. A significant spectral shift between the Soret maxima of TcO (410–413 nm) and ReO (438–441 nm) corroles was observed and, based on two‐component spin–orbit ZORA TDDFT calculations, ascribed to relativistic effects in the Re case. The syntheses reported herein potentially pave the way toward ^99mTc‐porphyrinoid‐based radiopharmaceuticals.     

Overtone spectra of 2-mercaptoethanol and 1,2-ethanedithiol

Vibrational spectra of vapor-phase 1,2-ethanedithiol and 2-mercaptoethanol were recorded to investigate weak intramolecular interactions. The spectra were recorded with conventional absorption spectroscopy and laser photoacoustic spectroscopy in the 2000-11,000 cm(-1) region. The room temperature spectra of each molecule are complicated by contributions from several conformers. Anharmonic oscillator local-mode calculations of the OH- and SH-stretching transitions have been performed to facilitate assignment of the different conformers in the spectra. We observe evidence of hydrogen-bond-like interactions from OH to S, but not from SH to O or S. The OH to S intramolecular interaction in 2-mercaptoethanol is weak and comparable to that found in the OH to O interaction in ethylene glycol.