Yoichi Taguchi

Intramolecular oxyselenenylation and deselenenylation reactions in water, conducted by employing polymer-supported arylselenenyl bromide

Abstract After immobilizing arylselenenyl bromide on polymer resin, the oxyselenenylation reaction of olefin was carried out in water. An amphiphilic polymer-supported arylselenenyl bromide was employed, and various intramolecular oxyselenenylation and deselenenylation reactions proceeded smoothly in water in fair chemical yields (up to an 83% yield).

RING CURRENT EFFECTS OF PHENYL AND NAPHTHYL GROUPS : INTERNAL PROBES FOR DETERMINING THE ABSOLUTE CONFIGURATION OF CHIRAL AZETIDIN-2-ONES BY 1H NMR

Abstract The ring current effects of the phenyl and 1-naphthyl rings are used to determine the absolute configuration of ten chiral azetidinones prepared from the [2+2] cycloaddition of (S)-1-(1-naphthyl)ethyl and (S)-1-phenylethyl isocyanate to vinyl ethers under high pressure. The (S)-1-arylethyl group of the studied azetidinones adopts a preferred conformation that can be distinguished by 1 H NMR spectroscopy. The application of this principle to other azetidinones containing the arylethyl substituent is consistent with the configurations determined by chemical correlation and X-ray diffraction and verifies the reliability of the proposed method.

Solid-phase intramolecular oxyselenenylation and deselenenylation reactions using polymer-supported selenoreagents and their application to aqueous media organic synthesis

Polymer-supported organoselenium reagents with amide linker were readily prepared from substituted-polystyrene resins. Through the use of polymer-supported arylselenenyl bromides, the oxyselenenylation reaction of olefins was carried out even in water. An amphiphilic polymer-supported arylselenenyl bromide was employed, and the intramolecular oxyselenenylation and the subsequent deselenenylation reactions proceeded smoothly in water with fair chemical yields (up to an 83% total yield).

Configurational 1H NMR study of optically active 7-(1-phenylethyl)-2-oxa-7-azabicyclo[3.2.0]heptan-6-one derivatives using Pirkle’s alcohols and a chiral shift reagent

Four novel stereoisomers of 7‐(1‐phenylethyl)‐2‐oxa‐7‐azabicyclo[3.2.0]heptan‐6‐one were prepared under high pressure from [2+2] cycloaddition of the pure enantiomers of 1‐phenylethyl isocyanate and 2,3‐dihydrofuran. Their conformational preferences in solution and the absolute configurations of the bridgehead carbon atoms were unambiguously determined by 1H NMR spectroscopy using tris[3‐(2,2,2‐trifluoro‐1‐hydroxyethylidene)‐d‐camphorato]europium(III) and (R)‐ or (S)‐1‐(9‐anthryl)‐2,2,2‐trifluoroethanol (Pirkle’s alcohols). MM2 single‐point energy calculations were consistent with the experimentally determined stereochemistry. ©1998 John Wiley & Sons, Ltd.

Two-carbon extension of N,N-disubstituted amides with bis(trimethylsilyl) thioketene affording N,N-disubstituted 3-oxothioamides

N,N-Disubstituted alkanamides cleanly react with bis(trimethylsilyl)thioketene to form N,N-disubstituted 2-trimethylsilyl-3-trimethylsilyloxyalk-2-enethioamides, which upon acid hydrolysis give N,N-disubstituted 3-oxoalkenethioamides.

The Reaction of 1, 2-Epithiooctane with t-Butylamine

The reaction of 1, 2-epithiooctane with t-butylamine in a glass ampoule gave 1- (N-t-butylamino) -2-octanethiol (1) and 1- (N-t-butylaminomethyl) heptyl 2-mercaptooctyl sulfide (2). The ratio of (1) / [(1) + (2)] was high at the initial stage of the reaction, and decreased as the reaction proceeded. Excess t-butylamine caused no significant increase in the total yield. The addition of a small amount of alcohol promoted the reaction in a similar manner to the reaction of 1, 2-epithiooctane with secondary amine. (1) was concluded to be produced by a nucleophilic attack of t-butylamine on the terminal methylene of the ring of 1, 2-epithiooctane, and (2) to result from the reaction of the mercapto group of (1) with 1, 2-epithiooctane.

The Reaction of 1, 2-Epithiodecane with Secondary Amines

The reaction of 1, 2-epithiodecane with diethylamine in a glass ampoule gave 1- (N, N-diethylamine) -2-decanethiol. The ratio of yield vs. conversion, (Y) / (C), was about 50% for equal molar reaction. Excess amine raised (Y) / (C) to 60%. Though higher temperature promote the reaction, (Y) / (C) decreased. Polar solvents, particularly alcohols, promoted the reaction. The addition of a small amount of alcohol, water or acetic acid promoted the reaction in a glass tube at 80°C and increased (Y) / (C). Though the reaction of 1, 2-epithiodecane with pyperidine or molpholine gave 1-amino-2-decanethiols in good yield, the expected product could not be obtained without methanol for the reaction with N-methylaniline.The reaction mechanism was considered to be a nucleophilic attack of the amine on the terminal methylene of 1, 2-epithiodecane, activated by ammonium ions.

The Ring-opening Reaction of 1, 2-Epithiodecane with Mixtures of t-Butyl Alcohol and Other Alcohols

The ring-opening reaction of 1, 2-epithiodecane with a mixture of t-butyl alcohol and ethanol in the presence of sulfuric acid gave a mixture of 1-ethoxy-2-decanethiol (1), 2-ethoxy-1-decanethiol (2), 1-ethoxy-2- (t-butylthio) decane (3), 2-ethoxy-1- (t-butylthio) decane (4), 1-mercapto-2-decanol (5), and 1-t-butylthio-2-decanol (6). The product distribution varied with reaction time, amounts of sulfuric acid, and molar ratio of t-butyl alcohol to ethanol, the ratio of (4) to total products increased with longer reaction time or larger amounts of sulfuric acid.Among these products, it was proved that (5) and (6) were formed via the reaction of 1, 2-epithiodecane with t-butyl alcohol. The formation of (3), (4), and (6) are reasonably explained in terms of intermediacy of the episulfonium (7) which is formed by the attack of t-butyl cation to 1, 2-epithiodecane.The reaction of 1, 2-epithiodecane with a mixture of t-butyl alcohol and methanol, 1-propanol or 2-propanol in the presence of sulfuric acid gave the products corresponding to (4), and the order of these yields was methanol>ethanol>1-propanol>2-propanol.

The Reaction of 1, 2-Epithioalkanes with Acetyl Chloride

The reaction of 1, 2-epithiodecane with acetyl chloride gave a mixture of S- [1- (chloromethyl) nonyl] thioacetate (1) and S- (2-chlorodecyl) thioacetate (2), and a polymer. The ratio of the yields of (1) and (2) was little changed with the reaction conditions such as reaction temperature, reaction time, and kinds of solvents, and it was about 6 : 4. The yields of (1) and (2), however, became higher when polar solvents such as acetone, ethyl methyl ketone, DMF, acetonitrile, acetic anhydride, and acetic acid were used.The reaction of 1, 2-epithiooctane, 1, 2-epithiododecane, and 1, 2-epithiotetradecane with acetyl chloride gave similar results to the reaction of 1, 2-epithiodecane with acetyl chloride.The reaction is presumed to be attack of chloride ion of acetyl chloride to 1, 2-epithioalkanes.

The Reaction of 1, 2-Epithioalkanes with Alcohols in the Presence of Acids

The reaction of 1, 2-epithiodecane (I) with methanol in the presence of sulfuric, p-toluenesulfonic, and methanesulfonic acids gave a mixture of 2-methoxy-1-decanethiol (II), 1-methoxy-2-decanethiol (III), and a polymer. The ratio of the yields of II and III was little changed with the reaction conditions such as reaction temperature, reaction time, and kinds and amounts of acids, and it was about 6 : 4. Each NMR spectrum of the polymers formed under various conditions showed that the ratio of [CH3- (CH2)7, -CH-CH2-] / [CH3O-] was 24. The reaction of 1, 2-epithiooctane, 1, 2-epithiododecane, and 1, 2-epithiotetradecane with methanol, and I with other primary alcohols in the presence of sulfuric acid gave similar results described above. On the other hand, the reaction of I with secondary alcohols in the presence of sulfuric acid gave almost the same amounts of 2-alkoxy-1- and 1-alkoxy-2-decanethiols. The reactivities of alcohols to 1, 2-epithioalkanes were primary > secondary>tertiary alcohols.