Masao Tokuda

Dimerization of anilines and benzylamines with mercury(II) oxide-iodine reagent

Abstract By treatment with mercury(II) oxide-iodine reagent in dichloromethane at room temperature, substituted anilines were transformed to the corresponding azobenzenes. A similar treatment of benzylamines and benzhydrylamine gave N-benzylidenebenzylamines and N-benzhydrylidenebenzhydrylamine, respectively. α-Alkyl-substituted benzylamines gave diazenes and the corresponding phenyl ketones, competitively. An azine was obtained by interaction with the reagent of a benzylamine carrying an electron-withdrawing substituent at the α position, such as ethyl phenylglycinate.

Facile and stereoselective synthesis of (E)-vinyl bromides by microwave-induced reaction of 1,1-dibromoalkenes using a diethyl phosphonate/EtONa/EtOH system

(E)-Vinyl bromides were readily prepared from 1,1-dibromoalkenes by microwave irradiation within 1 min using a diethyl phosphonate/EtONa/EtOH system. This method utilizes cheap and environmentally friendly reagents, requires only a short reaction time, and gives (E)-vinyl bromides in high stereoselectivities and high yields.

Cyclization of aminyl radicals generated by anodic oxidation of lithium alkenylamides. Stereo- and regioselective synthesis of cis-l-alkyl-2, 5-disubstituted pyrrolidines

Abstract Neutral aminyl radicals (3) generated by anodic oxidation of lithium alkenylanides (2) were found to undergo a stereo- and regioaelective cyclization to give cis -1-alkyl-2, 5-disubatituted pyrrolidines (5c–5h) in moderate yields. The cis stereochemistry of 5c–5h was confirmed by comparison with the corresponding trans -1-allkyl-2, 5-disubstituted pyrrolidines which were prepared by aminomercuration of 1c–1h. The structure of trans -1,2-dimethyl-5-phenylpyrrolidine (17) was established by an X-ray crystallographic analysis of its ammonium bromide 21. Various aminyl radicals examined in this study were found to combine exclusively with the internal carbon of their double bond to give a five- (5a–5l) or six-membered ring (13). No product arising from the cyclization is obtained from N-methyl-1-phenylbut-3-enylamine (14).

Convenient and stereoselective synthesis of (Z)-1-bromo-1-alkenes by microwave-induced reaction

Abstract ( Z )-1-Bromo-1-alkenes were stereoselectively prepared in high yields in a short reaction time (0.2–1.0 min) by microwave irradiation of the corresponding 2,3-dibromoalkanoic acids in DMF in the presence of triethylamine.

Aminyl radical cyclization by means of anodic oxidation. Stereoselective synthesis of cis-1-methyl-2,5-disubstituted pyrrolidines

Abstract Neutral aminyl radicals generated by anodic oxidation of lithium alkenylamides 2 undergo a stereoselective cyclization to give cis -1-methyl-2,5-disubstituted pyrrolidines 4. Their cis stereochemistry was confirmed by a comparison with trans -1,2-dimethyl-5-phenylpyrrolidine, the structure of which was established by X-ray crystallographic analysis of its quarternary ammonium bromide 6.

Facile synthesis of aryl-substituted 2-alkenoic acids by electroreductive carboxylation of vinylic bromides using a magnesium anode

Electrochemical carboxylation of phenyl-substituted vinylic bromides in the presence of atmospheric carbon dioxide using a platinum cathode and a magnesium anode gave the corresponding α,β-unsaturated carboxylic acids in 63–92% isolated yields. A precursor of ibuprofen, 2-(p-isobutylphenyl) propenoic acid, was readily obtained in a 93% yield by a similar electrochemical carboxylation of 1-bromo-1-(p-isobutylphenyl)ethene. Stereochemical studies showed that thermodynamically less stable Z-isomers were preferentially produced from either E- or Z-vinylic bromides in these electrochemical carboxylations.

Stereoselective synthesis of 4- or 5-substituted 2-benzyl- and 2-benzoylpyrrolidines by means of anodic oxidation of δ-alkenylamines

Abstract The anodic oxidation of the lithium amides of δ-alkenylamines 6a, 6b, 6c, 10a , and 10b gave stereoselectively cis -5-substituted 2-benzyl-1-methylpyrrolidines ( 7a,7b,7c ) and 4-substituted 2-benzyl-1-methyl-pyrrolidines ( 11a, 11b ) in high yields. The anodic oxidation of N -methoxyl compounds of δ-alkenylamines ( 12a, 12b ) gave 5-substituted 2-benzoyl-1-methylpyrrolidines ( 13a, 13b ).

Synthesis of isoindolobenzazepine alkaloids based on radical reactions or Pd(0)-catalyzed reactions.

Methods for synthesis of a ring system characteristic of isoindolobenzazepine alkaloids were studied. Synthesis of lennoxamine and a formal synthesis of chelenine were accomplished in a short route via radical or Pd(0)-catalyzed cyclization as the key step. An altenative approach based on a radical migration of a cyano group or Pd(0)-catalyzed carbonylation was also developed for both alkaloids.

New electrochemical carboxylation of vinyl triflates. Synthesis of β-keto carboxylic acids

Abstract Electrochemical reduction of alicyclic vinyl triflates ( 1a-1e ) in a DMF solution containing 0.1 M Bu 4 NBF 4 under an atmospheric pressure of carbon dioxide with a platinum cathode and a magnesium anode resulted in the cleavage of an oxygen-sulfur bond of 1 to give the corresponding β-keto carboxylic acids ( 2a-2e ) in yields of 28–77%.

Regioselective synthesis of β,γ-unsaturated acids by the electrochemical carboxylation of allylic bromides using a reactive-metal anode

Electrolysis of γ-mono and disubstituted allylic bromides in the presence of atmospheric pressure of carbon dioxide using a platinum cathode and a magnesium anode gave regioselectively the corresponding γ-mono and disubstituted β,γ-unsaturated carboxylic acids in 34–71% yields.