Toshikazu Ibata

Enantioselective synthesis of cis-2-oxazoline-4-car☐ylates by Lewis acid catalyzed formal [3 + 2] cycloadditions of 5-alkoxyoxazoles with aldehydes

Abstract Formal [3 + 2] cycloaddition of 2- o -methoxyphenyl-5-methoxyoxazole with benzaldehyde, m - and p - substituted benzaldehydes in the presence of 30 mol% of ( R )-methylaluminum β-binaphthoxide, which was prepared from ( R )-2,2′-dihydroxy-1,1′-dinaphthyl and 1.1 - 1.05 equiv. of trimethylaluminum, gave cis -2-oxazoline-4-car☐ylates in high enantoselectivity.

Stereocontrol of metal-catalyzed cycloaddition of carbonyl ylide with N-substituted maleimide

Abstract The CuOTf (20 mol%) or CuClYb(OTf)3 (5 mol%) catalyzed decomposition of o-(methoxycarbonyl)-α-diazoacetophenone in the presence of N-methylmaleimide gave 1,3-dipolar cycloadducts in an endo-selective manner (endo:exo = 94:6). On the other hand, the Rh2(OAc)4-catalyzed (5 mol%) reaction gave cycloadducts with exo-selectivity (endo:exo = 11:89).

Synthesis of highly substituted pyridines through nucleophilic substitution of tetrachloro-3-cyanopyridine

Tetrachloro-3-cyanopyridine reacts with anilines and/or sodium azide through replacement of three chlorine atoms at the 2-, 4-, and 6-positions, whereas with difunctional nucleophiles by replacement of chlorines at the 5- and 6-positions. Using these reactions synthesis of highly substituted pyridines has been developed

Carbonyl ylide from 3-chloro-3-p-nltrophenylcarbene and acetone

Abstract 3-chloro-3-p-nitrophenylcarbene readily reacts with acetone to from carbonyl ylide which undergoes 1,3 cycloaddition with dipolarophiles.

Reactions of 5-alkoxyoxazoles with aldehydes in the presence of Lewis acid: regio- and stereoselective formation of 4-alkoxycarbonyl-2-oxazolines

Abstract The [3 + 2] cycloaddition of 5-alkoxyoxazoles with aldehydes in the presence of the organoaluminum reagent, which was prepared from (±)-2,2′-dihydroxy-1,1′-dinaphthyl and AlMe 3 , gave cis -4-alkoxycarbonyl-2-oxazolines in high regio- and stereoselective manner.

Formation of diazoketones and azines by improved oxidation of ketohydrazones using Cu(acac)2 as a catalyst

Abstract An efficient Cu(acac) 2 -catalyzed oxidation of ketohydrazones afforded the corresponding α-diazoketones or ketazines in high yields depending on the reaction conditions. However, the reaction of benzophenone hydrazone gave benzophenone azine without affording diphenyldiazomethane. The formation of azines is explained by the intermediacy of carbenoid generated by the Cu(acac) 2 -catalyzed decomposition of diazo compounds.

Structures of the novel dimers of 1-alkoxy-2-benzopyrylium-4-olates

Abstract The structure of novel type dimers of 1-methoxy- and 1-isopropoxy-2-benzopyrylium-4-olates was determined by spectroscopic and single-crystal X-ray structural analyses to have 4-alkoxy-5-(o-alkoxycarbonylphenyl)-4,7;5,6-bisepoxy-2-benzocycloheptan-1-ones.

Kinetic studies of chloro-p-nitrophenylcarbene with acetone and diethyl fumarate

Abstract The reaction of chloro-p-nitrophenylcarbene with acetone to form carbonyl ylide is not reversible.

Nitro group substitution reaction of 2,3,5,6-tetrachloronitrobenzene with primary and secondary amines under high pressure

Abstract The ratio of substitutions of nitro group and chlorine atom is affected by the bulkiness of amines in the aromatic nucleophilic substitution of 2,3,5,6-tetrachloronitrobenzene with various primary and secondary amines under high pressure of 0.6 GPa.

Reaction of oxazoles. Formation of abnormal Diels–Alder adducts of 5-methoxy-4-(p-nitrophenyl)oxazoles with tetracyanoethylene, and X-ray crystal structure of one of the products

The reaction of 2-alkyl or -aryl substituted 5-methoxy-4-(p-nitrophenyl)oxazoles (1) with tetracyanoethylene gave 2-substituted methyl 3,3,4,4-tetracyano-5-(p-nitrophenyl)-4,5-dihydro-3H-pyrrole-5-carboxylates (2) as formal [3 + 2] cycloadducts; these were produced via a zwitterionic mechanism involving oxazole ring opening.