Reaction of maleimides and ethyl 3-aminocrotonates. A reinvestiation leading to an improved synthesis of pyrrolo[3,4-c]pyridines

Abstract

Hz). l,4,6-Triphenylpyridinium-2-carboxylate (11). 2-(Ethoxycarbonyl)-1,4,6-triphenylpyridinium tetrailuoroborate (8a; 5 g, 10.7 mmol) was stirred at 25 °C as a suspension in aqueous NaOH (0.5 N, 25 mL, 12.5 mmol) for 24 h. The white solid was filtered off and washed with water (500 mL) and ether (50 mL) to give the betaine as microcrystals: 3.2 g (85%); mp 150 °C dec (satisfactory analysis not obtained due to decomposition on attempted recrystallization); IR (CHBr3) 1650 (s), 1618 (s) cm"1; NMR (CDC13/TFA) 7.S-7.9 (m, 15 ), 8.10 (d, 1 H, J = 2 Hz), 8.38 (d, 1 H, J = 2 Hz).1,2,4-Triphenylpyridinium iodide (13) was obtained by refluxing 1,4,6-triphenylpyridinium-2-carboxylate (11) (2 g, 5.7 mmol) with aqueous HI (65%, 1.20 g, 6.1 mmol) in THF (50 mL)for 4 h to yield yellow crystals (washed with ether). Recrystallization from absolute EtOH gave yellow needles: 2.1 g (85%); mp 273-274 °C; IR (CHBr3) 1630 cm"1; NMR (CDC13/TFA) 7.6-7.9 (m, 15 ), 8.

Asymmetric Reduction of Activated Alkenes by Pentaerythritol Tetranitrate Reductase: Specificity and Control of Stereochemical Outcome by Reaction Optimisation

“…2‐Methylmaleimide (2a) was synthesised according to the procedure described previously; yield: 5%;2,39 mp 104–106 °C (lit. mp 105 °C);2 1 H NMR (400 MHz, CDCl 3 ): δ =2.11 (d, J =1.6 Hz, 3 H), 6.34 (q, J =1.8 Hz, 1 H), 7.4 (bs, 1 H); anal.…”

Dearomatization of 3,5-dinitropyridines – an atom-efficient approach to fused 3-nitropyrrolidines

“…This result represents the first synthesis of derivatives of novel heterocyclic system -decahydrodipyrrolo[3,4-b:3',4'-d]pyridine. It should be noted that hydrogenated pyrrolo [3,4-c]pyridine core is an important scaffold since compounds of this class possess antibacterial 32 , and anticancer activity 33,34 as well as cognition activating properties. 35 The structures of compounds 7a-e were confirmed by NMR-spectroscopy and HRMS data, as well as X-ray diffraction study (for compounds 7a,b,e).…”

Recyclization Reactions of N-Arylmaleimides with Polynucleophilic Compounds*

“…At the same time, the presence of several reactive functional groups in the structure offers opportunities for using these compounds as substrates in the synthesis of new heterocyclic compounds. On the other hand, N-arylmaleimides are frequently used for molecular design of various heterocyclic linearly linked and condensed matrices [4][5][6][7][8][9][10]. Previously it has been demonstrated that N-arylmaleimides react as C(3)-electrophiles with various 1,4-bisnucleophiles, resulting in the formation of six-membered heterocyclic systems: piperidinones [6], hydrogenated thiazinones [11][12], and oxazinones [13].…”

“…Previously it has been demonstrated that N-arylmaleimides react as C(3)-electrophiles with various 1,4-bisnucleophiles, resulting in the formation of six-membered heterocyclic systems: piperidinones [6], hydrogenated thiazinones [11][12], and oxazinones [13]. At the same time, arylmaleimides react with 1,3-bisnucleophiles less predictably and may serve as С(3)-electrophiles, forming five-membered heterocyclic systems: pyrrolidines [4,8], imidazolinones [7], thiazolinones [14-16], or serve as С(4)-electrophiles, leading to six-membered heterocycles, respectively [7-9, 17]. Mixtures of five-membered and sixmembered heterocyclic systems are often formed [7,9].…”