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1. The aromatic Claisen rearrangement of a 1,2-azaborine

   https://doi.org/10.1039/d2ob02186b  

   Robichaud, Hannah M.; Ishibashi, Jacob S.; Ozaki, Tomoya; Lamine, Walid; Miqueu, Karinne; Liu, Shih-Yuan (May 2023, Organic & Biomolecular Chemistry)

   The first aromatic Claisen rearrangement of a 1,2-azaborine is described along with a quantitative kinetic comparison of the reaction of the azaborine with its direct all-carbon analogue. The azaborine A rearranged in a clean, regioselective fashion and reacted faster than the all-carbon substrate B at all temperatures from 140–180 °C. Activation free energies were extracted from observed first-order rate constants (A: Δ G ‡298K = 32.7 kcal mol −1 ; B: Δ G ‡298K = 34.8 kcal mol −1 ) corresponding to a twenty fold faster rate for A at observed reaction temperatures. DFT calculations show that the rearrangement proceeds via a concerted six-membered transition state and that the electronic structure of the BN and CC rings is mostly responsible for the observed regioselectivity and relative reactivity. 

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2. A Diiron(I/II) μ-1,2-Carbonyl Complex Relevant to CO Binding on Fe(111)

   https://doi.org/10.1021/acs.inorgchem.5c00759  

   John, Titto Sunil; Singh, Devender; Maurel, Vincent; García-Serres, Ricardo; Murray, Leslie J (June 2025, Inorganic Chemistry)

   Fischer–Tropsch conversion of syngas to hydrocarbons is proposed to begin with CO binding to the iron surface of the catalyst. CO adsorption on various iron facets of relevance to the Fischer–Tropsch process suggest that the Fe(111) surface is the most active for catalysis, and that CO bound to the penultimate layer of Fe atoms or the b-state is the resting state during catalysis. Notably, a μ-1,2 mode was discarded for the b-state due to a lack of exemplar molecular species and expectation that such a mode would have a higher energy infrared (IR) absorption than observed experimentally (viz. 1735–1860 cm–1). Here, we report the synthesis of a diiron(I/II) complex in which CO binds μ-1,2: (Fe(OTf))(Fe(THF)(μ-1,2-CO))L where L2– is a bis(β-diketiminate) cyclophane (1). Surprisingly, the observed νCO at 1763 cm–1 for 1 compares well with that reported for b-state. Electron paramagnetic resonance (EPR), Mössbauer, and density functional theory (DFT) results support a weakly coupled s = 3/2 iron(I) and s = 2 iron(II) pair. Reduction of 1 results in C–O cleavage and C–C bond formation to yield a ketenylidene (CCO) complex as a major product observed spectroscopically. 

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3. Crystal structure of bromido­penta­kis­(tetra­hydro­furan-κO)magnesium bis­[1,2-bis­(di­phenyl­phosphan­yl)benzene-κ2P,P′]cobaltate(−1) tetra­hydro­furan disolvate

   https://doi.org/S2056989019001671  

   Girigiri, P. B. (January 2019, Acta crystallographica)

   Structural characterization of the ionic title complex, [MgBr(THF)5][Co(dpbz)2]·2THF [THF is tetra­hydro­furan, C4H8O; dpbz is 1,2-bis­(di­phenyl­phosphan­yl)benzene, C30H24P2], revealed a well-separated cation and anion co-crystallized with two THF solvent mol­ecules that inter­act with the cation via weak C—H...O contacts. The geometry about the cobalt center is pseudo­tetra­hedral, as is expected for a d10 metal center, only deviating from an ideal tetra­hedral geometry because of the restrictive bite angles of the bidentate phosphane ligands. Three THF ligands of the cation and one co-crystallized THF solvent mol­ecule are each disordered over two orientations. In the extended structure, the cations and THF solvent mol­ecules are arranged in (100) sheets that alternate with layers of anions, the latter of which show various π-inter­actions, which may explain the particular packing arrangement. 

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4. Allenylidene Induced 1,2‐Metalate Rearrangement of Indole‐Boronates: Diastereoselective Access to Highly Substituted Indolines

   https://doi.org/10.1002/anie.202103108  

   Simlandy, Amit Kumar; Brown, M. Kevin (April 2021, Angewandte Chemie International Edition)

   Abstract A process to achieve 1,2‐metalate rearrangements of indole boronate as a way to access substituted indolines in high diastereoselectivities is presented. The reaction involves the generation of a Cu–allenylidene, which is sufficiently electrophilic to induce the 1,2‐metalate rearrangement. The scope of the reaction is evaluated as well as further transformations of the product. 

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5. Synthesis of enantiopure 1,2-azido and 1,2-amino alcohols via regioand stereoselective ring-opening of enantiopure epoxides by sodium azide in hot water

   https://doi.org/http://dx.doi.org/10.1016/j.tetasy.2015.12.002  

   Hai-Yang Wanga, Kun Huang (February 2016, Tetrahedron. Asymmetry)

   A practical and convenient method for the efficient and regio- and stereoselective ring-opening of enantiopure monosubstituted epoxides by sodium azide under hydrolytic conditions is reported. The ringopening of enantiopure styryl and pyridyl (S)-epoxides by N3
   in hot water takes place preferentially at the internal position with complete inversion of configuration to produce (R)-2-azido ethanols with up to 99% enantio- and regioselectivity, while the (S)-adamantyl oxirane provides mainly the (S)-1-adamantyl- 2-azido ethanol in excellent yield. In general, 1,2-amino ethanols were obtained in high yield and excellent enantiopurity by the reduction of the chiral 1,2-azido ethanols with PPh3 in water/THF, and then converted into the Boc or acetamide derivatives. 

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