IOSR Journal of Applied Chemistry (IOSR-JAC) e-ISSN: 2278-5736.Volume 12, Issue 9 Ser. I (September. 2019), PP 31-38 www.iosrjournals.org DOI: 10.9790/5736-1209013138 www.iosrjournals.org 31 |Page Preparation of N-arylmaleimides with PPh 3 -CBrCl 3 as reagent Areej Hashim, Thies Thiemann* Department of Chemistry, United Arab Emirates University, PO Box 15551, Al Ain, Abu Dhabi, United Arab Emirates Abstract : N-Arylmaleimides have been prepared from maleic acid monoaryl amides by the action of PPh 3 - CBrCl 3 in the presence of trimethylamine using acetonitrile as solvent. Keywords: Intramolecular imidation, modified Appel reagent, UV-VIS spectroscopy --------------------------------------------------------------------------------------------------------------------------------------- Date of Submission: 17-09-2019 Date of Acceptance: 02-10-2019 --------------------------------------------------------------------------------------------------------------------------------------- I. Introduction N-substituted maleimides 1 are versatile dienophiles in [4+2]-cycloaddition reactions [1,2] and reactive Michael acceptors [3,4]. Also, maleimides have been used as monomers in polymerization reactions to polyimides [5-8], which function as high temperature resins. The polymers are obtained through iterative cycloaddition reactions [9,10], Michael addition [11], or by free-radical mechanisms [12], where especially ortho-substituted maleimides can act as radical initiators under photoirradiation [13]. In addition, maleimides have been used as starting materials in tumour-drug research [4] and as linker units in further biochemical studies [14,15]. In their own right, N-arylmaleimides have been found to be fungicidal vs. Candida albicans and other Candida species [16]. N-Arylmaleimides 1 can be synthesized in a number of ways, where for many of the methods maleic anhydride (2) is the starting material. One of the most commonly used methods is a two step approach where anilines are reacted with maleic anhydride (2) first to give maleanilic acids 4 (see Scheme 1). In the next step maleanilic acid is reacted with NaOAc/Ac 2 O, where acetic anhydride (Ac 2 O) is also used as the solvent [17-19]. Other methods involve the ring closure of maleanilic acids 4 to N-arylmaleimides 1 utilizing the reagents acetyl chloride / triethylamine [20], trimethyl orthoacetate / triethylamine [21], or methanesulfonic acid in n-butanol [22]. Alternatively, there are limited ways to produce N-arylmaleimides 1 directly from maleic anhydride (2) via the reaction with anilines 3 such as when utilizing HMDS/ZnBr 2 [23] or (NH 4 ) 2 S 2 O 8 –DMSO [24] from the reaction of maleic acid with anilines 3 in the presence of phosphorus pentoxide [25]. In our previous interest to utilize N-arylmaleimides as dienophiles [2,26], we prepared the compounds via the more common method mentioned above, using NaOAc/Ac 2 O, but noted that during the work-up the necessary hydrolysis and subsequent neutralization of the excess amount of Ac 2 O with Na 2 CO 3 produced a lot of CO 2 . As we were submitting the final product mixtures to a rapid column chromatography to obtain highly pure N-arylmaleimides rather than relying on fractional crystallization, we were also open to develop any new synthetic method that would equally necessitate a chromatographic separation as the final purification step. At the same time we were looking at the possibility of using BrCCl 3 -PPh 3 as reagent to prepare amides and esters from carboxylic acids [27], and it was a natural continuation of this study to investigate whether the preparation of imides from carboxylic acids using BrCCl 3 -PPh 3 would also be possible. Here, we report on the preparation of N- arylmaleimides 1 from maleanilic acids 4 with BrCCl 3 -PPh 3 as reagent. N O O X 2 X 1 1 Fig. 1. Structure of N-arylmaleimide 1 as target structure.