An Improved Method for the Preparation of 1-Methyl-2-formyl-5-bromopyrrole

One-Pot Conversion of Carbohydrates into Pyrrole-2-carbaldehydes as Sustainable Platform Chemicals

“…Oxidation of pyrrole-2-carbaldehyde 14 to the corresponding carboxylic acid by sodium chlorite and hydrogen peroxide in phosphate buffer solution, followed by esterification (K 2 CO 3 , MeI), produced methyl pyrrole-2-carboxylate 17 in 62% yield (Scheme ). The azide reduction by catalytic hydrogenation, intramolecular amidation in refluxing toluene, and the known bromination using NBS (2.0 equiv) , finally produced (−)-hanishin 11 in 69% yield (23% overall yield from d -ribose).…”

“…The azide reduction by catalytic hydrogenation, intramolecular amidation in refluxing toluene, and the known bromination using NBS (2.0 equiv.) 22,24 finally produced (-)-Hanishin 11 in 69% yield (23% overall yield from D-ribose). We developed a practical one-pot conversion method of carbohydrates and primary amines with a stoichiometric oxalic acid in DMSO at 90 ºC for 30 min, in which N-substituted pyrrole-2-carbaldehydes 4 were obtained in 21~53% yields.…”

Synthesis and properties of novel second-order NLO chromophores containing pyrrole as an auxiliary electron donor

“…Towards such compounds, N-methylpyrrole-2carbaldehyde 1 was first prepared from N-methyl pyrrole via the Vilsmeier formylation in the presence of POCl 3 and N,Ndimethylformamide (DMF). 18 The synthesis of halopyrrole 4 was initially carried out according to the reference method 28 by forming an acetal of 1, followed by a bromination with NBS. Unfortunately, such an approach resulted in only low yields in our study.…”

“…The hydrolysis of 3 with hydrochloric acid gave bromopyrrole 4 with a total synthetic yield of 72%, which is much higher than that reported in the literature ($48%). 28 The synthesis of aminated pyrrole compounds 5, 6 and 7 was accomplished via a modified method reported by Alvarez-Builla and co-workers. 27 As shown in Scheme 1, 4 reacts with piperidine in toluene in the presence of Pd 2 (dba) 3 as a catalyst and BINAP as a ligand to give 5 in a very high yield of 96%.…”

Syntheses of S-Enantiomers of Hanishin, Longamide B, and Longamide B Methyl Ester from l-Aspartic Acid β-Methyl Ester: Establishment of Absolute Stereochemistry

“…Treatment of the crude material with sodium methoxide in methanol gave the corresponding methyl ester 4 . Deprotection of the amino group under classical conditions followed by heating led to formation of bicyclic compound 5 , which reacts readily with 2 equiv of N -bromosuccinimide to give the corresponding 4,5-dibromo derivative. The regioselectivity of this reaction was confirmed by 2D NMR correlation experiments (GCOSY, GHMQC, and GHMBC).…”