Kazuhiko Orito

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.

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.

Studies on Friedel-Crafts acylation of N-acetylhomoveratrylamine and preparation of 1-substituted 3,4-dihydro-6,7-dimethoxyisoquinolines

Lorsque le substituant en 1 des isoquinoleines obtenues est co-carboxyethyl, -propyl ou -butyl, on obtient ulterieurement des pyrrolo [2,1-a] isoquinoleines, benzo [a] quinolizines et azepino [2,1-a] isoquinoleines

Exclusive 1,4-aryl migration in a stereoselective cyclization of N-benzylalk-4-enylaminyl radicals

Abstract Tandem cyclization of N -benzylalk-4-enylaminyl radicals readily occurs to give 1,4-aryl migration pyrrolidines, trans - N -methyl-2-alkyl-5-(1-phenylalkyl)pyrrolidines, exclusively.

A GENERAL AND STEREOSELECTIVE SYNTHESIS OF THE CAPSAICINOIDS VIA THE ORTHOESTER CLAISEN REARRANGEMENT

Abstract Capsaicin, a main pungent principle of hot pepper, and its 15 analogs have been efficiently synthesized. The key step of this synthetic sheme is the orthoester Claisen rearrangement, which transformed allylic alcohols 2A-C to (E)-alkenoates 3A-C ( E Z > 100 ) in a highly stereoselective manner. The subsequent carbon chain elongations on 3 based on the cyanation or the malonic acid ester synthesis afforded (E)-alkenoic acids 8, which were converted to the corresponding acid chloride and then coupled with vanillylamine to give capsaicinoids. HPLC and CE (capillary electrophoresis) analyses of these capsaicinoids were also carried out.

A new stereo- and regioselective synthesis of (±)-sesamin involving a β-scission of alkoxyl radicals as the key step1☆

Abstract A new stereo- and regioselective synthesis of (±)-sesamin (a representative lignan) based on our general method for the transformation of a cyclopentanone ring into a tetrahydrofuran ring involving a regioselective β-scission of the alkoxyl radicals is reported.

The stereochemistry of dihydrojervine and related compounds : The ORD curves of 11-oxoetiojervanes and 11-oxoiminojervanes☆

Abstract The configurations of C 12 , C 13 (and C 17 ) in an acetolysis product (IVa) of diacetyltetrahydrojervine (IIIa) and its derivatives (Va to VIIIa) have been established. It follows that dihydro- and tetrahydrojervine are correctly represented by formulas II and III, (C/D trans , 12βH) rather than XXXV and XXIX (C/D cis , 12αH), respectively. The stereochemistry of the hydrogenation results of jervine (I) and the related compounds is rationalized on the basis of these formulas and the spectral data. The ORD curves of 12-epimeric 11-oxoetiojervanes and 11-oxoiminojervanes with established configurations are also presented and the summarized result reveals that the amplitudes fall within the limits of −150 ∼ −190° for the C/D trans -fused compounds and of −70 ∼ −100° for the cis -fused.

Tandem cyclization of N-allylaminyl radicals: Stereoselective synthesis of 1,2,5-trisubstituted pyrrolizidines

Abstract Radical reaction of N -allylalk-4-enylaminyl radicals, generated from the corresponding N -chloroamines by treatment with Bu 3 SnH-AIBN in refluxing toluene, was carried out. Tandem cyclization of the resulting neutral aminyl radicals readily took place steroselectively to give 1,2,5-trisubstituted pyrrolizidines and a pyrroloindole derivative as a sole product in good yields. The cyclization products contained only two stereoisomers in each reaction, indicating that both of the consecutive cyclizations proceeded in a stereoselective manner.

Studies on carboxylation of alkoxy-substituted benzyl alcohols via direct lithiation and bromine-lithium exchange: Synthesis of phthalides and phthalideisoquinoline alkaloids

Abstract Conversion of alkoxy-substituted benzyl alcohols to the corresponding phthalides by carboxylation via ortho lithiation and bromine-lithium exchange was studied. The method was applied to the key step in the synthesis of phthalideisoquinoline alkaloids.

Stereoselective synthesis of 2-methylenepyrrolizidines by tandem cyclization of N-propargylaminyl radicals

Abstract Tandem cyclization of N-propargylaminyl radicals, generated by N-chlorination of (E)-alk-4-enylamines 2a–d and 2f followed by treatment with tributyltin radical, afforded 2-methylenepyrrolizidines 3a–d and 3f in a highly stereoselective manner. A similar radical cyclization of (Z)-N-propargyl-1-methyl-5-phenylpent-4-enylamine ( 2e ) gave pyrrolizidine 3b having the same stereochemistry as that obtained from the E isomer 2b .