Catalyst and Additive‐Free Selective Ring‐Opening Selenocyanation of Heterocycles with Elemental Selenium and TMSCN

Abstract

A catalyst and additive‐free strategy for selective ring‐opening selenocyanation of saturated heterocycles with elemental selenium and TMSCN is developed, affording a series of aliphatic selenocyanates and selenaheterocycles. In the case of unprotected unstrained N‐heterocycles, the reactions offer ammonium selenonitriles that prove to be an efficient selenonitrile reagent.

α-Selective C(sp3)–H Thio/Selenocyanation of Ketones with Elemental Chalcogen

“…Based on the mechanistic studies and previous work, we propose that the reaction (Scheme ) starts with the generation of sulfur (selenium) biradical A via homoscission of the X–X bond. The radical addition of biradical A with Me 3 SiCN affords intermediate B , which is converted into intermediate C along with the release of a trimethylsilyl radical.…”

Synthesis of Organoselenium Compounds with Elemental Selenium

“…Apart from β‐hydroxy aryl selenides and β‐hydroxy alkynyl selenides, various aliphatic selenocyanates such as β to δ‐hydroxy selenocyanates and β to γ‐amino selenocyanates were prepared through selective ring‐opening selenocyanation of saturated heterocycles using elemental selenium as selenium source in the absence of a catalyst or an additive (Scheme 41). [82] The reaction displayed high efficiency and regio‐ and stereo‐selectivity towards a wide range of saturated heterocycles including strained three‐ and four‐membered rings as well as unstrained five‐membered rings. Furthermore, the employment of unprotected saturated N ‐heterocycles as the substrate afforded selenium‐containing heterocycles instead of β‐amino selenocyanates probably due to the strong nucleophilic of free amines.…”

Organic Selenocyanates: Rapid Advancements and Applicationsin the Field of Organic Chemistry

“…[45] Recently, Wu and coworkers published a fantastic approach for the specific ring-opening reaction of saturated O-/Nheterocyclic compounds (124/126) with elemental Se and TMSCN in the absence of catalysts and additives, revealing a straightforward avenue to aliphatic selenocyanates (125) (Scheme 65a) along with Se-containing heterocycles (127/128). [46] For both symmetric and unsymmetric epoxides (124), the reaction was furnished well under an N 2 atmosphere, producing βhydroxy selenocyanated products (126) with good to excellent yields and high regioselectivity. Encouraged by the aforementioned transformation, this technique was then extended to the ring-opening selenocyanation of N-Ts-substituted aziridines (126), yielding β-amino selenocyanate compounds (127) with good regio-and stereo-selectivities.…”

“…Notwithstanding, the author highlighted the significance of selenocyanated products (125) in the laboratory by synthesizing diselenide (131) and SeCF 3 -containing compounds (132) (Scheme 65d). [46] The authors presented a possible pathway in which a selenium biradical (A) formed in situ from Se 8 endures radical accumulation with TMSCN to construct an intermediary B, pursued by the unleashing of two TMS radicals to build C. On the one hand, the interaction of the TMS radical with i PrOH results in the formation of TMSO i Pr and H * . On the other hand, C liberates a Se 6 moiety to form D, which further interacts with the H * to produce the crucial intermediary E. The E facilitates the selective ring-opening of heterocompound 126, resulting in the creation of the selenocyanate product 127.…”

“…Although the tension of unstrained N-heterocycle is insufficient to initiate the ring-opening reaction, ammonium selenonitriles 130 were produced by the interaction of N-heterocycle 129 and E (Scheme 66). [46] In line with this area of research, Zhou and colleagues established a verdurous technique for the preparation of aryl selenocyanates (134) and selenaheterocyclic compounds (136) in the absence of metals or additives by combining Se powder and TMSCN. [47] A series of arylboronic acids (133 d-133 j) substituted with electron-neutral alkyl groups, electron releasing groups, electron accepting ones and halogens at various positions in the phenyl ring were selenocyanated in high to excellent yields (134 b-134 j).…”