Masashige Yamauchi

Reactivity of 2-methylene-1,3-dicarbonyl compounds: catalytic enantioselective Diels–Alder reaction

Abstract The catalytic enantioselective Diels–Alder reaction of 1,1-dicarbonylethenes 3 with cyclopentadiene in the presence of Ti-TADDOLs, Mg–Ph-box and Mg–Ph-mox complexes was investigated. Although both exo - and enantioselectivity with Ti-TADDOL catalysts were poor, they were much improved using Mg–Ph-box or Mg–Ph-mox complexes as chiral catalysts. Thus, 3 was an efficient two-point binding dienophile and the non- C 2 -symmetric Ph-mox 8 could be used as a chiral ligand.

Hetero-Diels–Alder reactions of 2-methylene-1,3-dicarbonyl compounds with alkyl vinyl ethers

2-Methylene-1,3-dicarbonyl compounds reacted with alky vinyl ethers in benzene to give hetero-Diels–Alder reaction products, 3,4-dihydro-2H-pyrans, regioselectively and/or chemoselectively.

Reactions of 2-methylene-1,3-dicarbonyl compounds with furan

The mono- and/or di-substituted furans (2 and 3) were synthesized by the reaction of 2-methylene-1,3-dicarbonyl compounds (1) with furan under moderate selectivity

Total synthesis of fulvic acid

Synthesis of fulvic acid (1a) was accomplished by a route involving selective ozonization of 9-propenylpyranobenzopyran (1c), obtained by a regioselective cyclization of the 2-methylsulphinylmethyl 1,3-dione(3c).

Reactivity of 2-methylene-1,3-dicarbonyl compounds. Inverse electron-demand Diels–Alder reactions with alkyl vinyl ethers

Highly regioselective hetero-Diels–Alder reactions were achieved by reaction of 2-methyene-1,3-dicarbonyl compounds 1 with alkyl vinyl ethers 2. This regioselectivity of the cycloadditions was consistent with the results that could be predicted by considering the frontier orbital of 1.

High asymmetric induction in the Diels−Alder reactions of 1-benzoyl-1-phenyl-menthyloxycarbonylethene

Lewis acid catalysed Diels–Alder reaction of 1-benzoyl-1-phenylmenthyloxycarbonylethene (1d) gave the exo adduct regio- and diastero-selectively.

Hydrolysis of α-cyanobenzylideneanilines. Part I. Kinetic studies in acidic media

The hydrolysis of α-cyanobenzylideneanilines was studied kinetically in aqueous sulphuric acid (H0–2 to –6), 40% aqueous acetonitrile (pH 3–0), and 60% aqueous dioxan (H0 1·5 to –2) at 25°. Benzoyl cyanide was demonstrated to be an intermediate. The rate of hydrolysis exhibited a maximum at H0ca.–1 to –2. The effect of substituents on the reaction rate and the Bunnett–Olsen ϕ values suggested that the hydration of the protonated substrate is rate determining on the less acidic side of the rate maximum and that the decomposition of the intermediate amino-alcohol is rate determining under more acidic conditions. It is suggested, from consideration of the shape of the acidity–rate profile, that aniline is expelled only from the dipolar form (or zwitterionic form) of the amino-alcohol intermediate, because the tendency for aniline to separate is weakened by the electronwithdrawing cyano-group.

Retinoids and related compounds. Part 20.1 Synthesis of(11Z)-8,18-ethanoretinal and a conformational study of therhodopsin chromophore

In order to investigate the conformation of the chromophore around the trimethylcyclohexene ring in rhodopsin, (11Z)-8,18-ethanoretinal 6 has been synthesized. Its binding experiment with bovine opsin afforded a new rhodopsin analogue, the opsin shift and CD spectrum of which were similar to those of natural rhodopsin. These experimental results strongly suggest that the torsional angle around the 6–7 single bond in rhodopsin corresponds to the torsional angle in (11Z)-8,18-ethanoretinal 6. In addition, MMX calculations for 2 and 6 have been carried out and are reported.

Enantioselective catalytic Diels–Alder reaction of ethyl 2-benzoylacrylate with chiral bis(oxazoline)– or mono(oxazoline)–magnesium complex

The magnesium catalysed Diels–Alder reaction of 2-benzoylacrylate gave the endo-adduct enantioselectively with bis(oxazoline) 5 as a C 2 -symmetric ligand or mono(oxazoline) 4 as a non-C 2 -symmetric ligand.

Studies on the syntheses of heterocyclic compounds containing benzopyrone. Part 5. Total synthesis of fulvic acid

Total synthesis of fulvic acid (1a) is described. Regioselective cyclization of the enedione (8f), an equivalent of the proposed biogenetic intermediate (5a) for citromycetin (2), gave the pyrone (11a), which led to fulvic acid (1a) by a route involving debenzylation, selective ozonization, and hydration.