A Simple Zinc-Mediated Method for Selenium Addition to Michael Acceptors
作者:Francesca Giulia Nacca、Bonifacio Monti、Eder João Lenardão、Paul Evans、Claudio Santi
DOI:10.3390/molecules25092018
日期:——
biphasic Zn/HCl-based reducing system. Alkenes with a variety of electron-withdrawing groups were investigated in order to gauge the scope and limitations of the process. Results demonstrated that the addition to acyclic α,β-unsaturated ketones, aldehydes, esters amides, and acids was effectively achieved and that alkyl substituents at the reactive β-centre can be accommodated. Similarly, cyclic enones
Reactions of selenium with imines (RR1CNR2) of aldehydes and ketones in the presence of carbon monoxide, water and triethylamine lead to reductive selenation, on aerobic work-up, to afford symmetrical diselenides (RR1CHSe)2 in good to excellent yields. The proposed mechanism suggests that both in situ generated carbonyl selenide (SeCO) and hydrogen selenide (H2Se) are involved in the reaction.
ABSTRACT A one-pot and efficient synthesis of dialkyl dichalcogenides (S, Se) in aqueous media under catalyst-free conditions using benzylic, allylic and primary halides with elemental sulfur and selenium has been developed. Also, this procedure was extended to preparation of trisulfides and triselenides from secondary and tertiary halides in same condition. In all cases, products can be obtained in good
Various Se,O-heteroacetals were prepared by the LiAlH4 reduction of diselenides 1 followed by alkylation with methoxymethyl chloride or (2-methoxyethoxy)methyl (MEM) chloride. Olefinic and acetylenic alpha-seleno carbenium ions were generated by the selective C-O bond cleavage of O-(2-methoxyethyl)-Se,O-heteroacetals with titanium(IV) chloride and cyclized to give the seleno heterocyclic compounds. Olefinic MEM-selenides 3a,b,d-f,h underwent the endo-mode cyclization to afford 4-chloroselenacycloalkanes 4a,b,d-f,h in good yields, whereas acetylenic MEM-selenides 12b-e,g-j underwent the exo-mode cyclization to give 3-(1-chloroalkylidene)selenacycloalkanes 13b-e,g-j. This new utilization of alpha-seleno carbenium ions was also applied to the intramolecular and intermolecular Friedel-Crafts reactions.
Access to 3-alkylselenindoles by multicomponent reaction of indoles, selenium powder and unactivated alkyl halides under transition-metal-free conditions
作者:Huan Liu、Zhong-Jian Cai、Shun-Jun Ji
DOI:10.1016/j.cclet.2022.01.046
日期:2022.9
Herein, we reported a convenient and efficient multicomponent reaction of indoles, selenium powder and unactivated alkyl halides. This protocol provides a practical, and facileapproach for the synthesis of 3-alkylselenindole derivatives. The advantages of this strategy include mild and transition-metal-free conditions, broad functional group tolerance, the use of simple and easily accessible seleniium