Hiroshi Suginome

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.

A stereospecific synthesis of conjugated (E, Z)- and (Z, Z)-alikadienes by a palladium-catalyzed cross-coupling reaction of 1-alkenylboranes with 1-alkenyl bromides

Abstract The reactions of ( Z )-1-alkenyldisiamylboranes with ( Z )- or ( E )-1-alkenyl bromides in the presence of a catalytic amount of tetrakis(triphenylphosphine)palladium and sodium ethoxide gave the corresponding conjugated ( Z , Z )- or ( Z , E )-alkadiene with high stereospecificity. The reactions of ( E )-1-alkenyl-1,3,2-benzodioxaboroles with ( Z )- or ( E )-1-alkenyl bromides similarly gave the corresponding coupled products while retaining the configurations of the starting alkenylboranes and the alkenyl bromides.

A simple new general synthesis of macrocyclic ketones: A new entry to the synthesis of exaltone and (±)-muscone☆

Abstract We describe an efficient new synthesis of 15-membered cyclic ketones, exaltone and (±)-muscone, based on a three-carbon annelation of cyclic ketones followed by the regioselective radical cleavage of the fused bond of the resulting bicyclic systems.

New general synthesis of medium ring-lactones via a regioselective β-scission of alkoxyl radicals generated from catacondensed lactols

Abstract We describe a new general method for the synthesis of medium-sized lactones based on ring-enlargement via a regioselective β-scission of alkoxyl radicals generated by photolysis from the hypoiodites of several catacondensed lactols. The syntheses of 9-membered lactones from 6 5 fused lactols, 10-membered lactones including a naturally occurring lactone, phoracantholide I, from 6 6 or 7 5 fused lactols, and 11-membered lactones from 7 6 or 8 5 fused lactols are shown to be achieved by the present method. This new method may have a potential for application to the synthesis of either smaller or larger-sized lactones.

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).

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.

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 ).

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.

New stereo- and regiospecific synthesis of humulene by means of the palladium-catalyzed cyclization of haloalkenylboranes

Abstract We describe a new stereo- and regiospecific synthesis of humulene, the major sesquiterpene of hops, by means of the palladium-catalyzed cyclization of haloalkenylboranes derived from geranyl halides via 4 principal steps.

New short step general synthesis of isobenzofuran-1(3H)-ones (phthalides) based on a single or double β-scission of alkoxyl radicals generated from 1-ethyl-benzocyclobuten-1-ols and from 1,3-dihydroisobenzofuran-1-ols; synthesis of some natural phthalides

Abstract New general methods are described for the synthesis of phthalides, 3-monosubstituted, and 3,3-disubstituted phthalides including naturally-occurring phthalides such as pierardine based on a regioselective single or double β-scission of the alkoxyl radicals generated by the photolysis of the hypoiodites of 1-ethyl benzocyclobuten-1-ols or 1,2-catacondensed benzocyclobuten-1-ols or 1,3-dihydro-1,3-alkanoisobenzofuran-1-ols. The formation paths of the phthalides, which involve a regioselective single or double β-scission of the alkoxyl radicals generated from 1-alkylbenzocyclobuten-1-ols and from catacondensed benzocyclobuten-1-ols, are discussed.