228411-98-1Relevant articles and documents
Selenoether ligand assisted Heck catalysis
Chakraborty, Tapash,Srivastava, Kriti,Singh, Harkesh B.,Butcher, Ray J.
experimental part, p. 2559 - 2564 (2011/07/09)
Selenoether ligands, 2,2′-methylenebis(selanediyl)bis(2,1-phenylene) dimethanol (5), (2,2′-(ethane-1,2-diylbis(selanediyl))bis(2,1-phenylene)) dimethanol (6) and (2-(benzylselanyl)phenyl)methanol (7) have been synthesized by reducing di-o-formylphenyl diselenide and reacting the in situ generated selenolate with dibromomethane, 1,2-dibromoethane and benzyl chloride, respectively. The ligands, bis(2-(4,4-dimethyl-4,5-dihydrooxazol-2-yl) phenylselanyl)methane (8) and 1,2-bis(2-(4,4-dimethyl-4,5-dihydrooxazol-2-yl) phenylselanyl)ethane (9) have been synthesized similarly from bis[2-(4,4-dimethyl-2-oxazolinyl)phenyl] diselenide using electrophiles dibromomethane and 1,2-dibromoethane, respectively. Activity of ligands 5-9 along with 2-(2-(benzylselanyl)phenyl)-4,4-dimethyl-4,5-dihydrooxazole (10) and 1-(2-(benzylselanyl)phenyl)-N,N-dimethylmethanamine (11) were examined for the Heck reaction of aryl halides with olefins. Bidentate Se,N ligand 11 was found to be the best one in the series and constitutes an efficient phosphine-free catalytic system with PdCl2. The catalytic system showed moderate activity for the coupling of activated aryl chlorides in the presence of tetra-n-butyl ammonium bromide (TBAB). Complexes [10-PdCl2] (12) and [11-PdCl2] (13) have shown marginally better activity in comparison to the in situ generated catalysts from PdCl2 and 10 and 11, respectively in the coupling of 4-bromoacetophenone with n-butylacrylate. Ligand 9 and complex 13 have been characterized by single crystal X-ray diffraction analysis.
Optical resolution and configurational stability of selenoxides stabilized by intramolecular coordination
Shimizu, Toshio,Enomoto, Masao,Taka, Hideo,Kamigata, Nobumasa
, p. 8242 - 8247 (2007/10/03)
2-((Dimethylamino)methyl)phenyl alkyl (or aryl) selenoxides, configurationally stabilized by intramolecular coordination of an amino group to the selenium atom, were optically resolved into their enantiomeric isomers by means of high-performance liquid chromatography using an optically active column packed with amylosecarbamate derivative/silica gel. This is the first example of the isolation of optically pure selenoxides without bulky substituents and also the first isolation of optically pure alkyl aryl selenoxides. The absolute configuration of the (-)-isomers could be assigned to be the S-form by comparison of their specific rotations, circular dichroism spectra, and behavior on the optically active column with those of the sulfur analogue, prepared by Andersen's method. Racemization of the optically active selenoxides was accelerated not only in acidic solution but also in basic media. This result indicates there are two different mechanisms for their racemization in acidic and basic media. The stabilization energy of the selenoxides by the intramolecular coordination of an amino group to the selenium atom was estimated to be ca. 3 kcal mol-1 on the basis of variable-temperature 1H NMR measurements.
