title: Asymmetric cycloaddition reactions of diazoesters with 2-alkenoic acid derivatives catalyzed by binaphthyldiimine-Ni(II) complexes.
abstract: The catalytic activity of chiral binaphthyldiimine (BINIM)-Ni(II) complexes for asymmetric enantioselective diazoalkane cycloadditions of ethyl diazoacetate with 3-acryloyl-2-oxazolidinone and 2-(2-alkenoyl)-3-pyrazolidinone derivatives was evaluated. The cycloadditions of 3-acryloyl-2-oxazolidinone and its 5,5-dimethyl derivative, in the presence of the BINIM-Ni(II) complex (10 mol %; prepared from (R)-BINIM-4Ph-2QN (ligand C) and Ni(ClO(4))(2)·6H(2)O) afforded 2-pyrazolines having a methine carbon substituted with an oxazolidinonyl group in moderate ratios (70:30 to 72:28), along with high enantioselectivities (90-92% ee) via 1,3-proton migration. On the basis of the investigations on the counteranions of the Ni(II) complex, the N-substituent of pyrazolidinone, and reaction temperatures, the optimal enantioselectivity (97% ee) and ratio (85:15) of 2-pyrazoline were obtained for the reaction of 2-acryloyl-1-benzyl-5,5-dimethyl-3-pyrazolidinone in the presence of (R)-BINIM-4Ph-2QN-Ni(II) ((R)-C/Ni(II)) complex prepared using Ni(BF(4))(2)·6H(2)O. In the cases of 1-benzyl-2-crotonoyl-5,5-dimethyl-3-pyrazolidinone, 1-benzyl-2-(2-butenoyl)-5,5-dimethyl-3-pyrazolidinone, and 1-benzyl-5,5-dimethyl-2-(3-ethoxycarbonyl)propenoyl-3-pyrazolidinone, the use of the (R)-BINIM-2QN-Ni(II) ((R)-A/Ni(II)) complex gave good to high enantioselectivities (85-93% ee) with the sole formation of the 2-pyrazoline having a methine carbon substituted with a pyrazolidinonyl group. Relatively good enantioselectivity (77% ee) was observed for the reaction between 2-acryloyl-5,5-dimethyl-1-naphthylmethyl-3-pyrazolidinone and an α-substituted diazo ester, ethyl 2-diazo-3-phenylpropanoate, which has yet to be employed as a diazo substrate in asymmetric cycloaddition reactions catalyzed by a chiral Lewis acid.
authors.affiliation: Department of Chemistry and Material Engineering, Faculty of Engineering, Shinshu University, Wakasato, Nagano 380-8553, Japan. sugahio@shinshu-u.ac.jp
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Suga
authors.forename: Yasuhisa
authors.initials: Y
authors.lastname: Furihata
authors.forename: Atsushi
authors.initials: A
authors.lastname: Sakamoto
authors.forename: Kennosuke
authors.initials: K
authors.lastname: Itoh
authors.forename: Yukihisa
authors.initials: Y
authors.lastname: Okumura
authors.forename: Teruko
authors.initials: T
authors.lastname: Tsuchida
authors.forename: Akikazu
authors.initials: A
authors.lastname: Kakehi
authors.forename: Toshihide
authors.initials: T
authors.lastname: Baba