Kazunobu Harano

Reaction of aromatic N-oxides with dipolarophiles. XVII. Cycloaddition behavior of allenes toward pyridine N-oxides and formation of azetidine-type cycloadduct

3,5-Dimethylpyridine N-oxide was allowed to react with phenylsulfonylpropadiene in CHCl 3 at room temperature to give a mixture of the 1:1 [1,5] sigmatropic rearrangement product and the 1:2 azetidine-type cycloadduct. The structure of the azetidine-type cycloadduct was determined by single crystal X-ray analysis. The reaction behavior and the regioselectivity are discussed in terms of the frontier molecular orbital considerations

Novel [4+6]π cycloadduct from frontier-controlled pericyclic reaction of 2,5-dimethoxycarbonyl-3,4-diphenylcyclopentadienone with cyclooctatetraene

Abstract Treatment of 2,5-dimethoxycarbonyl-3,4-diphenylcyclopentadienone with an excess of cyclooctatetraene gives the novel exo[4+6]π cycloadduct together with the endo[2+4]π and bis-Diels-Alder cycloadducts. The CNDO/2 MO calculation indicates that HOMO(COT)-LUMO(cyclopentadienone) interaction will be more important than the other.

Periselective cycloaddition of tricarbonyliron complexes of 7-membered ring unsaturated compounds with dichlorocarbene. Masking effect of tricarbonyliron group and reactivity of cycloadducts

Abstract Dichlorocarbene(DCC) showed significant differences of periselectivity in reactions between 7-membered ring unsaturated compounds with masking and without masking by the tricarbonyliron group. Tricarbonyl[N-(ethoxycarbonyl)-azepine]iron (7) and tricarbonyl(cycloheptatriene) iron (8) gave tricarbonyl[N-(ethoxycarbonyl)-2,3-homoazepine]iron derivative (9) and tricarbonyl (2,3-homocycloheptatriene)iron derivative (10). Oxidative degradation of these adducts (9 and 10) with trimethylamine N-oxide afforded N-(ethoxycarbonyxl)-2,3-homoazepine derivative (11) and 2,3-homocycloheptatriene derivative (12). By contrast, treatment of 2 equivalents of o-chloranil with these adducts (9 and 10) gave two types of novel spiroadducts (13a and 13b); (14a and 14b), respectively. The structure of adduct 13a was fully established by X-ray analysis.

High periselectivity of cyclocoupling reactions of 2-oxyallyl cation with cycloheptatrieneiron tricarbonyl

Abstract The cyclocoupling reaction of 2-oxyallyl-Fe(II) cation ( 1 ) with cycloheptatrieneiron tricarbonyl ( 4 ) gave the σ,π-allyliron tricarbonyl complex ( 6 ). Structure of the complex ( 6 ) was fully established by X-ray analysis. Oxidative degradation of the complex ( 6 ) with o-chloranil afforded a single iron free compound ( 7 ) which was indicated that a carbonyl insertion took place during oxidation.

Molecular structures of endo[4+2]π and exo[6+4]π cycloadducts via cycloaddition reaction of n-ethoxycarbonylazepine with 2,5-dimethoxycarbonyl-3,4-diphenylcyclopentadienone

Abstract The cycloaddition reaction of N-ethoxycarbonyl-1H-azepine with 2,5-dimethoxycarbonyl-3,4-diphenylcyclopentadienone gave anti-endo [4+2]π and exo [6+4]π cycloadducts. These structures were fully identified by X-ray crystallographic techniques. Mechanism for their cycloaddition reactions are also discussed.