Malaysian Journal of Analytical Sciences Vol 20 No 6 (2016): 1241 - 1246

DOI: http://dx.doi.org/10.17576/mjas-2016-2006-02

 

 

 

SYNTHESIS OF ISOXAZOLIDINE VIA 1,3-DIPOLAR CYCLOADDITION OF N-4-TERT-BENZYLIDENE NITRONE AND MALEIMIDE IN IMIDAZOLIUM-BASED IONIC LIQUIDS

 

(Sintesis Sebatian Isoxazolidina Melalui Tindakbalas 1,3-Dwikutub Pensiklotambahan

N-4-Tetra-Benzilidina Nitron dan Maleimida dalam Cecair Ionik Berasaskan Imidazolium)

 

Nur Liyana Sakinah Johari, Siti Nashwa Mohd Poad, Nur Hasyareeda Hassan, Nurul Izzaty Hassan*

 

School of Chemical Science and Food Technology, Faculty of Science and Technology,

Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia.

 

*Corresponding author: drizz@ukm.edu.my

 

 

Received: 1 April 2016; Accepted: 11 August 2016

 

 

Abstract

The development of environmentally friendly methodologies for pericyclic reactions such as Diels Alder reaction is astonishing. Nevertheless, this is still scarce for the rest of pericyclic reactions. In this work, diastereosiomeric cycloadducts were formed via 1,3-dipolar cycloaddition between  N-4-Tert-Benzylidene nitrone and  maleimide in  imidazolium-based  ionic  liquids (ILs) at 25 °C. Cycloaddition between nitrone 1 and maleimide 2 give diastereoisomeric adducts with 1:1 and 1:2 trans/cis ratio in two ionic liquids, [Bmim][PF₆] and [Bmim][BF₄], respectively. [Bmim][PF₆] give the desired cycloadducts in 43% yield compared to only 18% yield in [Bmim][BF₄]. In comparison, when the similar reaction was conducted in chloroform, the diasteroeisomeric mixture favoured trans isomer in 6:0.2 ratio. We reasoned that the repulsive van der Waals interactions favouring exo transition state was assisted by imidazolium ionic liquids. Thus, ILs have shown great potential as second reaction media in dipolar cycloaddition reactions.

 

Keywords:  pericyclic reactions, 1,3-dipolar cycloaddition, imidazolium ionic liquids

 

Abstrak

Tindak balas Diels Alder merupakan contoh tindak balas perisiklik yang mesra alam serta mendapat perhatian ramai. Namun begitu, contoh lain tindak balas perisiklik masih lagi terhad. Melalui kajian ini, tindak balas 1,3-dwikutub pensiklotambahan di antara N-4-Tetra-Benzilidina nitron dan maleimida dalam cecair ionik imidazolium pada suhu 25 °C telah dijalankan. Pensiklotambahan antara nitron 1 dan maleimida 2 telah menghasilkan sikloaduk diastereoisomerik dengan nisbah tran/cis 1:1 dan 1:2 bagi kedua-dua cecair ionik, [Bmim][PF₆] dan [Bmim][BF₄]. Hasil sikloaduk dalam cecair ionik [Bmim][PF₆] adalah sebanyak 43% berbanding hanya 18% di dalam [Bmim][BF₄]. Apabila tindak balas yang sama dijalankan dalam pelarut kloroform, ianya memberikan sikloduk diastereosiomerik dalam nisbah 6:0.2 dengan menyebelahi isomer trans. Kami beranggapan bahawa interaksi repulsif Van der Waals mendorong keadaan peralihan ekso dengan bantuan cecair ionik imidazolium. Oleh yang demikian, cecair ionik mampu memainkan peranan penting sebagai media kedua di dalam tindak balas dwikutub pensiklotambahan.

 

Kata kunci:  tindak balas perisiklik, 1,3-dwikutub pensiklotambahan, cecair ionik imidazolium

 

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