Kiyoshi Honda

A Novel Highly Effective Chiral Lithium Amide for Catalytic Enantioselective Deprotonation of meso-Epoxides

Abstract A highly enantioselective deprotonation of meso -epoxides was achieved by a catalytic amount of a new chiral lithium amide, derived from (2 S ,3a S ,7a S )-2-(pyrrolidin-1-ylmethyl)octahydroindole, in the presence of excess lithium diisopropylamide to afford the corresponding allylic alcohol derivatives up to 94% ee.

Enantioselective addition of dialkylzinc to aldehydes catalyzed by (S)-2-(N,N-disubstituted aminomethyl)indoline

Abstract Chiral di- or triamines, ( S )-2-( N , N -disubstituted aminomethyl)indoline 1a – d , derived from ( S )-indoline-2-carboxylic acid were efficient chiral catalysts for the enantioselective addition of dialkylzincs to aldehydes. The best results were obtained by employing 15 mol% of ( S )-2-(4-methylpiperazin-1-ylmethyl)indoline 1c , and chiral secondary alcohols were obtained in up to 97% ee.

Base-mediated rearrangement of free aromatic hydroxamic acids (ArCO-NHOH) to anilines.

Without using activating agents, a variety of free aromatic hydroxamic acids could be rearranged to aromatic amines in the presence of base alone.

Facile synthesis and desulfurization of 5-(phenylthio)pyrano[3,2-c][1]benzopyrans starting from 5-phenylthio-4-penten-1-ols and salicylaldehyde via in situ intramolecular cycloaddition of substituted o-quinonemethides

5-(Phenylthio)pyrano[3,2-c][1]benzopyrans (6) were successfully synthesized in high yield by the reaction of 5-phenylthio-4-penten-1-ol (5) and salicylaldehyde (1) in benzene in the presence of p-toluenesulfonic acid and trimethyl orthoformate. trans,trans-Isomer 6a and cis,cis-isomer 6d were produced as major products from (E)-5 and (Z)-5, respectively. Treatment of 6a with lithium 4,4′-di-tert-butylbiphenyl or Raney Ni (W-4) lead to trans-pyrano[3,2-c][1]benzopyran 4b which is very difficult to make by direct cycloaddition using unsubstituted 4-penten-1-ol (2b).

Synthesis and physical properties of novel liquid crystals containing pyranobenzopyrans as a core structure

The synthesis and physical properties of pyranobenzopyran ring system have been studied as a core structure of novel liquid crystal (LC) compounds. Substituted pyranobenzopyrans having an alkoxy group on the A ring (benzene ring) exhibited smectic and nematic phase, those having a fluoro-substituted phenyl group on the A ring exhibited wider range of smectic phase. When the latter are added to a base LC mixture (ZLI-1565, Merck), the clearing point was raised. Interestingly, pyranobenzopyrans having a trifluoromethyl phenyl group or a cyano group on the A ring showed an extremely large positive dielectric anisotropy.

Stereocontrolled synthesis of acyclic terpenoids viaN-ylide [2,3]rearrangement of ammonium salts with the stereodefined isoprene unit

Stereocontrolled elongation of a functionalized isoprene unit on the E or Z terminal methyl of terpenoids was achieved by N-ylide rearrangement of the common ammonium salts under selected reaction conditions. A 1,5-diene or conjugated triene skeleton can be furnished by reductive or oxidative removal of the amino group of the rearrangement product, respectively. As an application to natural-product synthesis, all-(E)-terpenoid (E)-11d and (E,Z)-terpenoid (Z)-11c were converted into β-sinensal and (13Z)-retinol, respectively. General aspects of these transformations and a plausible transition state for the N-ylide rearrangement are discussed.

Enantiomerically enriched bicyclic hydroxamic acids in one step from α-aminohydroxamic acids and keto acids via cyclocondensation

Abstract New enantiomerically enriched bicyclic hydroxamic acids, 1-hydroxy-dihydro-1H-pyrrolo[1,2-a]imidazole-2,5(3H,6H)-diones, have been synthesized by the cyclocondensation of L-α-aminohydroxamic acids with keto acids in a highly chemo- and stereoselective manner. The cis configuration between the amino acid side chain and the methyl group at C7a in 1H-pyrrolo[1,2-a]imidazole-2,5-dione was unambiguously established by X-ray crystallographic analysis. This method could also be applied to the cyclocondensation with o-formylbenzoic acid, giving a tricyclic hydroxamic acid in a good yield. Supplemental materials are available for this article. Go to the publishers online edition of Synthetic Communications® to view the free supplemental file. GRAPHICAL ABSTRACT

Tandem Brook Rearrangement/Silicon Polonovski Reaction via Oxidative Generation of Ammonium Ylides

A tandem Brook rearrangement/silicon Polonovski reaction has been achieved by in situ generation of ammonium ylides via the oxidation of α-silyl-tertiary amines. Furthermore, we found that the oxidation of N-(1-cyano-1-silyl)methyl-tertiary amines with peracids induced the tandem Brook rearrangement/silicon Polonovski reaction/fragmentation to give formamide derivatives in moderate yields.