“Tris(pentafluorophenyl)borane-Catalyzed Stereospecific Bromocyanation of Styrene Derivatives with Cyanogen Bromid"
Kensuke Kiyokawa*, Ikumi Noguchi, Takaya Nagata, and Satoshi Minakata*
Org. Lett. ASAP. DOI:10.1021/acs.orglett.3c00727

Abstract: We herein report on the bromocyanation of styrene derivatives with cyanogen bromide in the presence of tris(pentafluorophenyl)borane which functions as a Lewis acid catalyst that can effectively activate cyanogen bromide. This reaction proceeds through a stereospecific syn-addition. The protocol is operationally simple and provides practical access to β-bromonitriles.

“Stereospecific Oxycyanation of Alkenes with Sulfonyl Cyanide"
Kensuke Kiyokawa*, Miu Ishizuka, and Satoshi Minakata*
Angew. Chem. Int. Ed., 2023, 62, e202218743/1–7. DOI:10.1002/anie.202218743

Abstract: Oxycyanation of alkenes would allow the direct construction of useful β-hydroxy nitrile scaffolds. However, only limited examples of such reactions have been reported, and some problems including limited substrate scope and the lack of diastereocontrol in the case of the oxycyanation of internal alkenes have arisen. We herein report on the intermolecular oxycyanation of alkenes using p-toluenesulfonyl cyanide (TsCN) in the presence of tris(pentafluorophenyl)borane (B(C₆F₅)₃) as a catalyst, affording products that contain a sulfinyloxy group and a cyano group at the vicinal position. The reaction features a stereospecific syn-addition. The reaction also shows a broad substrate scope with good functional group tolerance. Mechanistic investigations by experimental studies and density functional theory (DFT) calculations revealed that the reaction proceeds via an unprecedented stereospecific mechanism through the electrophilic cyanation of alkenes, in which B(C₆F₅)₃ efficiently activates TsCN through the coordination of the cyano group to the boron center.

“α-Amination of Carbonyl Compounds by Using Hypervalent Iodine-Based Aminating Reagents Containing a Transferable (Diarylmethylene)amino Group"
Daichi Okumatsu, Kazuki Kawanaka, Shunpei Kainuma, Kensuke Kiyokawa*, and Satoshi Minakata*
Chem. Eur. J., 2023 29, e202203722/1–7. DOI:10.1002/chem.202203722

*Selected as the "Cover Feature" of the issue!

Abstract: Hypervalent iodine-based aminating reagents containing a transferable (diarylmethylene)amino group can be used for the α-amination of simple carbonyl compounds such as esters, amides, and ketones in the presence of a lithium base. The (diarylmethylene)amino groups of the products can be readily modified thus providing access to primary amines and diarylmethylamines. The developed method features transition-metal-free conditions and a simple one-pot procedure without the need to prepare enolate equivalents separately, thus offering a general and practical approach to the synthesis of a wide variety of α-amino carbonyl compounds. Experimental mechanistic investigations indicate that this amination proceeds through a unique radical coupling of an α-carbonyl radical with an iminyl radical which are generated through a single-electron transfer between a lithium enolate and the hypervalent iodine reagent.

“3,11-Diaminodibenzo[a,j]phenazine: Synthesis, Properties, and Applications to Tröger's Base-Forming Ladder Polymerization"
Saika Izumi, Keiki Inoue, Yuya Nitta, Tomoya Enjou, Takahiro Ami, Kouki Oka, Norimitsu Tohnai*, Satoshi Minakata, Takanori Fukushima, Fumitaka Ishiwari*, and Youhei Takeda*
Chem. Eur. J., 2023 29, e202202702/1–6. DOI:10.1002/chem.202202702

*Invited as a part of a Special Collection on "Novel Aromatics (ISNA 19)"!

Abstract: A new class of diamino-substituted π-extended phenazine compound was synthesized, and its photophysical properties were investigated. The U-shaped diaminophenazine displayed photoluminescence in solution with moderate quantum yield. The diamino aromatic compound was found applicable to the poly-condensation with formaldehyde to form Tröger’s base ladder polymer. The obtained microporous ladder polymer features high CO2 adsorption selectivity against N2, most likely due to the presence of basic nitrogen atoms in the phenazine rings.