Access to Variously Substituted 5,6,7,8‐Tetrahydro‐3H‐quinazolin‐4‐ones via Diels–Alder Adducts of Phenyl Vinyl Sulfone to Cyclobutene‐Annelated Pyrimidinones

Abstract

Keywords:Nitrogen heterocycles / Michael addition / Cycloaddition / 5,6,7,8-Tetrahydro-3H-quinazolin-4-ones Under basic conditions (Et 3 N, dioxane), the aromatic amidines 4 and also S-methylisothiourea 4g cleanly undergo Michael addition to methyl 2-chloro-2-cyclopropylideneacetate (5), followed by intramolecular nucleophilic substitution, cyclopropyl to cyclobutyl ring enlargement, deprotonation and cyclization with elimination of methanol to afford the cyclobutene-annelated pyrimidinones 6 in 43-83 % yield (7 examples). Thermal cyclobutene-ring opening of the latter at 175°C followed by regioselective Diels-Alder cycloaddition with phenyl vinyl sulfone gives the 2-aryl-6-(phenylsulfonyl)-5,6,7,8-tetrahydroquinazolinone derivatives 12 in 39-83 % yield (7 examples). Base-induced elimination of ben-

MCRs reshaped into a switchable microwave-assisted protocol toward 5-aminoimidazoles and dihydrotriazines

“…Of note, benzamidine and 3-nitrobenzamidine hydrochloride are commercially available, and other amidines were prepared by means of a reported procedure. 23 In summary, the new imidazole-forming MCR is an example of a 3-component-4-center reaction.…”

Synthesis of meso‐Substituted Tetrabenzotriazaporphyrins: Easy Access to Hybrid Macrocycles

“…Our investigations remained focused on the preparation of 5 . So, following the methodology reported by Hellal and Cuny,10 4‐bromobenzonitrile was treated with LiHMDS and hydrolyzed to give the HCl salt of the bromoamidine 8 (Scheme ) 11. Treatment of 8 with 4‐methoxyphenylacetylene under palladium catalysis leads to cross‐coupling and cyclization, thus yielding the precursor 9 directly and in good yield.…”

Antiproliferative effect on HepaRG cell cultures of new calix[4]arenes. Part II

“…The 1 H NMR spectrum of 6 showing the characteristic two doublets at 3.21 and 4.45 ppm (J = 13.35 Hz) for the bridging ArCH2Ar protons indicates a cone structure for compound 6. The tetra-nitrile calix [4] arene 6 was then converted to the tetra-amidine calix [4] arene 7 by the action of lithium trimethylsilylamide (LiN(TMS) 2 ) in THF following by acid hydrolysis [56,57]. The reaction of hydroxylamine in DMSO solution on the tetra nitrile 6 resulted in the formation of the desired tetra-amidoxime calix [4]arene 8 [58].…”