Hiroshi Igeta

Akio Ohsawa; Heihachiro Arai; Hidefumi Ohnishi; Takashi Itoh; Terumitsu Kaihoh; Mamiko Okada; Hiroshi Igeta

Oxydation par Pb(OAc) 4 , PbO 2 /acide trifluoroacetique et/ou peroxyde de nickel/acide acetique

Takashi Tsuchiya; Heihachiro Arai; Hiroshi Igeta

Abstract Photolyses of unsubstituted and methyl substituted pyridazine 1-oxides afforded the corresponding cyclopropenyl ketones (6) and furans (7), respectively. Photolysis of 3-phenyl-, 3-methoxy-and 3-hydroxy-pyridazine 1-oxides afforded furans alone, whereas 3-aminopyridazine 1-oxides gave levulinonitriles and 3-cyanopropionaldehydes (11). Mechanism of their formation are discussed.

Akio Ohsawa; Takashi Itoh; Kazuhiro Nagata; Terumitsu Kaihoh; Mamiko Okada; Chikako Kawabata; Heihachiro Arai; Hidefumi Ohnishi; Kentaro Yamaguchi; Hiroshi Igeta; Yoichi Iitaka

The reactivity of unsubstituted 1,2,3-triazine was investigated using various nucleophilic and electrophilic reagents, molecular orbital calculations, and low temperature nmr measurements

Akio Ohsawa; Heihachiro Arai; Hiroshi Igeta; Toshio Akimoto; Akio Tsuji; Yoichi Iitaka

Abstract Products, generated from a photolysis of 1,2-dioxides ( 1 ) of unsubstituted ( a ), 3- Me -( b ), 4- Me -( c ), 3,6-di Me ( d ), 3- Ph -( e ), 3- Me -6- Ph -( f ) and 3,6-di Ph -(g) pyridazines, have been investigated. Dioxides ( 1a–g ) afforded 3a, 6a -dihydroisoxazolo[5,4-d]isoxazoles ( 2a-g ). Dioxides ( 1e and 1g ) afforded 3-phenylisoxazole( 7 ) besides 2 . The structure of 2a was examined by X-ray crystallography. The compound 2d was also obtained by oxidation of the hexa-3-ene-2,5-dione dioxime. A mechanism generating those products has been speculated.

Akio Ohsawa; Terumitsu Kaihoh; Hiroshi Igeta

Monocyclic 1,2,3-triazines reacted with Grignard reagents to form adducts due to N-2 and C-5 attack together with β-substituted acrylaldehydes and N--substituted pyrazoles; the results show that the N-2,C-4 and C-5 positions are reactive towards Grignard reagents.

Akio Ohsawa; Heihachiro Arai; Hidefumi Ohnishi; Hiroshi Igeta

Alkyl substituted monocyclic 1,2,3-triazines and their 1-and 2-oxides have been synthesized; catalytic reduction (on Pd–C) of the triazines afforded their 2,5-dihydro compounds.

Hiroshi Igeta; Toshiko Nakai; Takashi Tsuchiya

Reaction of 5,6-benzo-1,2,4-triazine 1-oxides with phenylmagnesium bromide results in ring fission to afford benzimidazoles and 2-acylaminoazobenzenes.

Heihachiro Arai; Akio Ohsawa; Katsunori Saiki; Hiroshi Igeta; Akio Tsuji; Toshio Akimoto; Yoichi Iitaka

The 1,4,6,7-dioxadiazocin structure (3), which was originally assigned to the photo-isomers of pyridazine 1,2-dioxide (1), is incorrect; chemical data and X-ray analysis show the correct structure to be 3a,6a-dihydroisoxazolo[5,4-d]isoxazole (2).

Heihachiro Arai; Akio Ohsawa; Katsunori Saiki; Hiroshi Igeta

Irradiation of pyridazine 1,2-dioxides in dichloromethane afforded 1,4,6,7-dioxadiazocins as major products, together with the deoxygenated pyridazines.

Takashi Tsuchiya; Chisato Kaneko; Hiroshi Igeta

Reaction of N-methoxypyridazinium salts with hydroxide ion results in ring-opening to give vinyl diazomethanes in high yields.