Microwave‐assisted copper powder‐catalyzed coupling and cyclization of β‐bromo‐α,β‐unsaturated amides with amidine hydrochlorides leading to pyrimidinones

Abstract

β-Bromo-α,β-unsaturated amides are coupled and cyclized with amidine hydrochlorides using microwave irradiation in the presence of a catalytic amount of copper powder and a base to give the corresponding pyrimidinones in good yields.

Modern Development in Copper‐ and Nickel‐Catalyzed Cross‐Coupling Reactions: Formation of Carbon‐Carbon and Carbon‐Heteroatom bonds under Microwave Irradiation Conditions

“…Subsequently, the cyclized product (quinazolinone) is produced through the condensation between amino and carboxylic acid groups, as illustrated in Scheme 39. [115] A series of pyrimidinones and azole-fused pyrimidinones were similarly synthesized in a single step from the coupling and cyclization reactions of β-bromo α,β-unsaturated carboxylic acids and β-bromo-α,β-unsaturated amides with amidine hydrochlorides [116] or benzimidazoles. [117] Using copper powder as a catalyst and sodium tert-butoxide as a base in DMF, high yields were obtained with amide precursors, while carboxylic acid derivatives afforded the products in moderate yields (Scheme 40).…”

Recent Advances in Microwave-Assisted Copper-Catalyzed Cross-Coupling Reactions

“…Copper or its salts as catalyst under microwave irradiation has been extensively studied for the construction of heterocyclic systems. For examples, 3,5-disubstituted isoxazoles from the natural maslinic and oleanolic acids [82], 1,2-disubstituted indoles from α-aminonitriles and 2-halobenzyl halides [83], 3,3-disubstituted oxindoles from oxidative cyclization of acrylamide derivatives with non-activated ketones [84], substituted pyrroles via tandem copper-catalyzed propargylation/alkyne azacyclization/isomerization reaction [85], aziridines through Kinugasa conditions [86], fused imidazo heterocycles via multi-component reaction [87], 5-alkylamino-1H-pyrazole-4-carbaldehydes [88], 3,4diaryl isoquinolines using N-tert-butyl-o-iodobenzaldimine, phenylacetylene and iodobenzene as starting materials [89], pyrimidinones from the coupling and cyclization of βbromo-α,β-unsaturated amides with amidine hydrochlorides [90,91], pyrimidinones using three component Biginelli reaction [92], 3-N-sulfonylamidine coumarins via four component coupling reaction [93], 2H-pyran-2-ones from the cycloaddition of β-bromo-α,βunsaturated carboxylic acids with 1,3-diketones [94], furoquinoxalines from 2-amino substituted anilines, ethyl glyoxalate, and terminal alkynes through tandem A 3 coupling followed by a 5-endo-dig cyclization process [95], 5,6-dihydroindolo[1,2-a]quinoxaline derivatives via intramolecular N-arylation [96], isoquinolines and pyridines under multicomponent reaction of β-halovinyl/aryl aldehyde, aromatic/aliphatic terminal alkyne and tert-butylamine/benzamidine [97] and from o-bromoarylaldehydes, terminal alkynes, and aqueous ammonia [98], 2-aminooxazolo [4,5-b] pyridines through intramolecular C-O bond formation in aqueous medium [99], chiral nopinane-annelated pyridines from the reaction of pinocarvone oxime with enamines [100], dihydropyridines from substituted aromatic aldehydes using Hantzsch synthesis [101], pyrazole-based heterocycles via domino annulation [102], 2,6-diaminopyridines through amination of halopyridines [103], pyrazoles via N-arylation [104], phenylethynyl[1,2,4]methyltriazines from the cross coupling of 5-methyl-3-methyl-thio [1,2,…”