title: The reaction of 2-amino-4H-pyrans with N-bromosuccinimide.
abstract: The reaction of racemic 2-amino-4H-pyrans, such as 3-amino-1-aryl-1H-benzo[f]chromene-2-carbonitriles, with N-bromosuccinimide (NBS), in CH2Cl2, at room temperature, is a very quick, regio, stereoselective, and high yielding process, affording major racemic (1S, 2S)-2-bromo-3-imino-benzo[f]chromene or racemic (1S, 2S)-2-bromo-3-(bromoimino)-benzo[f]chromene derivatives, when using 1.0 or 2.2 equivalents of NBS, respectively. This reaction, extended to isomeric 2-amino-4-aryl-4H-benzo[h]chromene-3-carbonitriles, showed an unexpected reactivity, affording racemic (3S,4S)-3-bromo-2-(bromoimino)-benzo[h]chromene-3-carbonitriles or 2-oxo-2H-benzo[h]chromene-3-carbonitriles, when using 2.2 or 1.0 equivalents of NBS, respectively. The reaction of alkyl 6-amino-5-cyano-2-methyl-4H-pyran-3-carboxylates has yielded unstable racemic (3S,4S)-alkyl 3-bromo-2-(bromoimino)-3-cyano-6-methyl-3,4-dihydro-2H-pyran-5-carboxylates. The mechanism of these reactions has been investigated by computational methods.
authors.affiliation: Laboratorio de Química Médica, IQOG (CSIC), Juan de la Cierva, 3, 28006, Madrid, Spain, samadi72@yahoo.com.
authors.forename: Abdelouahid
authors.initials: A
authors.lastname: Samadi
authors.forename: Daniel
authors.initials: D
authors.lastname: Silva
authors.forename: Mourad
authors.initials: M
authors.lastname: Chioua
authors.forename: Lourdes
authors.initials: L
authors.lastname: Infantes
authors.forename: Elena
authors.initials: E
authors.lastname: Soriano
authors.forename: José
authors.initials: J
authors.lastname: Marco-Contelles
mesh_terms: D001974:Bromosuccinimide / Q000737:chemistry*; D060326:Chemistry Techniques, Synthetic; D008958:Models, Molecular; D011714:Pyrans / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D011714:Pyrans; D001974:Bromosuccinimide