Heihachiro Arai

Oxidation of 1-aminopyrazoles and synthesis of 1,2,3-triazines

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

Photochemistry—IX : Formation of cyclopropenyl ketones and furans from pyridazine N-oxides by irradiation

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.

The reactivity of monocyclic 1,2,3-triazine

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

Photochemistry—xiii1: The photokomerization of pyridazine 1 ,2-dioxides: formation of 3a,6a-dihydroisoxazolo[5,4-d]isoxazole

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.

Synthesis, oxidation, and reduction of monocyclic 1,2,3-triazines

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.

Correction to the structure of the photo-isomers of pyridazine 1,2-dioxides; X-ray crystal structure analysis

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).

Photolysis of pyridazine 1,2-dioxides; formation of the novel 1,4,6,7-dioxadiazocin ring system

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

Photolysis of tetrazolo[1,5-b]pyridazines; formation of cyanocyclopropenes

Irradiation of tetrazolopyridazines affords 3-cyanocyclopropens (20–25%) and 3-cyanopyrazoles (0·1%) by elimination of two or one molecules of nitrogen, respectively.

Photolysis of pyridazine N-oxides; formation of cyclopropenyl ketones

Irradiation of pyridazine N-oxides with primary amines in dichloromethane gives N-substituted pyrroles, suggesting that cyclopropenyl ketones are intermediates.