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Stereoselective aziridination of imines via ammonium ylides: A molecular electron density theory study
Author(s) -
Jalali Hamideh,
Hosseini Seyed Javad,
AliAsgari Safa,
Izadi Nia Jafar
Publication year - 2020
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.3798
Subject(s) - chemistry , nucleophile , electrophile , dabco , medicinal chemistry , transition state , regioselectivity , density functional theory , computational chemistry , nucleophilic substitution , ylide , double bond , octane , stereochemistry , organic chemistry , catalysis
The highly trans ‐stereoselective reaction of ammonium salt ( AS 2 ) toward (E)‐ N ‐benzylidene‐4‐methylbenzenesulfonamide ( IM 4 ) in the presence of Na 2 CO 3 leading to an aziridine derivative, trans ‐Az 6 , was theoretically studied using Molecular Electron Density Theory (MEDT) at the B3LYP/6‐31G(d) computational level to probe energy transformation, selectivities, and molecular mechanism. The reaction starts by a nucleophilic substitution reaction between 1,4‐diazabicyclo [2.2.2]octane ( DABCO ) and phenacyl bromide ( PB ) to form AS 2 which undergoes a proton abstraction by Na 2 CO 3 to produce Ammonium Ylide ( AY 3) . Subsequently, nucleophilic addition of AY 3 to the double bond in IM 4 leads to form a betaine‐like intermediate, namely, IN‐Ta which named IN‐Ta . Finally, trans ‐Az 6 is produced as a result of the nucleophilic attack of the negatively charged nitrogen atom on the carbon atom bearing DABCO in IN‐Ta . Analysis of the relative Gibbs free energies shows that the ring closure step is the rate‐determining step (RDS). By an investigation of the conceptual density functional theory, CDFT reactivity indices AY 3 and IM 4 are classified as a strong nucleophilic molecular system and as a strong electrophilic molecular system, respectively, which implies that the addition step of AY 3 to IM 4 has a high polar character. An analysis of the calculated electrophilic and nucleophilic Parr functions at the reactive sites of reagents clarifies the regioselectivity observed experimentally within the C 1 –C 2 bond creation process.