Magnesium-tartramide complex mediated asymmetric Strecker-type reaction of nitrones using cyanohydrin

An asymmetric Strecker-type reaction of nitrones using acetone cyanohydrin as a source of HCN has been realized. A magnesium-tartramide complex, generated from (R,R)-2,3-dihydroxy-1,4-di(pyrrolidin-1-yl)-butane-1,4-dione and MeMgBr, promoted transcyanation from the bromomagnesium salt of the cyanohydrin, in the presence of a catalytic amount of DBU, to afford the corresponding optically active (S)-α-amino nitrile derivatives. The reaction was applicable to various nitrones giving high-to-excellent enantioselectivities. © 2013 American Chemical Society

Magnesium-Alkoxide Directed Photoaddition of Tetrahydrofurans to γ,γ-Disubstituted Allylic Alcohols

Magnesium-alkoxide directed photoaddition of tetrahydrofurans to γ,γ-disubstituted allylic alcohols was achieved. When the allylic alcohols were treated with Grignard reagent in THF under light, the corresponding γ-(2-tetrahydrofuryl) substituted alcohols were regioselectively obtained in up to 82% yield. The conversion of the hydroxyl group to the corresponding bromomagnesium alkoxide was crucial.Embargo Period 24 month

(Z)-Selective enol triflation of α-alkoxyacetoaldehydes: Application to synthesis of (Z)-allylic alcohols via cross-coupling reaction and [1,2]-wittig rearrangement

The stereoselective transformation of α-alkoxyacetoaldehydes to the corresponding (Z)-vinyl triflates was achieved by treatment with phenyl triflimide and DBU. The stereochemistry was explained by the "syn-effect," which was attributed primarily to an σ → π∗ interaction. The β-alkoxy vinyl triflates obtained were applied to the stereoselective synthesis of structurally diverse (Z)-allylic alcohols via transition metal-catalyzed cross-coupling reaction and [1,2]-Wittig rearrangement. © 2015 American Chemical Society

Pre-steady-state kinetic studies of redox reactions catalysed by Bacillus subtilis ferredoxin-NADP+ oxidoreductase with NADP+/NADPH and ferredoxin

Ferredoxin-NADP+ oxidoreductase ([EC1.18.1.2], FNR) from Bacillus subtilis (BsFNR) is a homodimeric flavoprotein sharing structural homology with bacterial NADPH-thioredoxin reductase. Pre-steady-state kinetics of the reactions of BsFNR with NADP+, NADPH, NADPD (deuterated form) and B. subtilis ferredoxin (BsFd) using stopped-flow spectrophotometry were studied. Mixing BsFNR with NADP+ and NADPH yielded two types of charge-transfer (CT) complexes, oxidized FNR (FNRox)-NADPH and reduced FNR (FNRred)-NADP+, both having CT absorption bands centered at approximately 600 nm. After mixing BsFNRox with about a 10-fold molar excess of NADPH (forward reaction), BsFNR was almost completely reduced at equilibrium. When BsFNRred was mixed with NADP+, the amount of BsFNRox increased with increasing NADP+ concentration, but BsFNRred remained as the major species at equilibrium even with about 50-fold molar excess NADP+. In both directions, the hydride-transfer was the rate-determining step, where the forward direction rate constant (~ 500 s- 1) was much higher than the reverse one (< 10 s- 1). Mixing BsFdred with BsFNRox induced rapid formation of a neutral semiquinone form. This process was almost completed within 1 ms. Subsequently the neutral semiquinone form was reduced to the hydroquinone form with an apparent rate constant of 50 to 70 s- 1 at 10 °C, which increased as BsFdred increased from 40 to 120 μM. The reduction rate of BsFNRox by BsFdred was markedly decreased by premixing BsFNRox with BsFdox, indicating that the dissociation of BsFdox from BsFNRsq is rate-limiting in the reaction. The characteristics of the BsFNR reactions with NADP+/NADPH were compared with those of other types of FNRs. © 2016 Elsevier B.V. All rights reserved.Embargo Period 12 month

Stereoselective synthesis of (2 Z,4 E)-2,4-pentadien-1-ols via sequential 1,4-elimination reaction and [1,2]-wittig rearrangement starting from (E)-4-alkoxy-2-butenyl benzoates

The sequential 1,4-elimination reaction of (E)-4-alkoxy-2-butenyl benzoates and [1,2]-Wittig rearrangement gave (2Z,4E)-2,4-pentadien-1-ols stereoselectively. Z-Selective formation of intermediary vinyl ethers, whose stereochemistry was well elucidated by the "syn-effect", was achieved by treatment of the 2-butenyl benzoates with KOH in the presence of Pd catalyst. The subsequent [1,2]-Wittg rearrangement by use of n-BuLi proceeded with retention of the stereochemistry of the intermediary vinyl ethers. © 2013 American Chemical Society

Direct oxidation of 4-methylpyrrole-2-carboxylates with DDQ in the presence of a glycol

Oxidation of 4-methylpyrrole-2-carboxylates with DDQ in the presence of a glycol proceeded smoothly on the methyl group at the C4 position regioselectively to afford the corresponding pyrrole-2,4-dicarboxylates directly. Direct oxidation of a methyl group of 2,4,6-trimethylphenol and 3-methyl-9H-carbazole into carboxylates was also demonstrated. © 2012 The Japan Institute of Heterocyclic Chemistry

One-pot stereoselective synthesis of 2-acylaziridines and 2-acylpyrrolidines from N-(propargylic)hydroxylamines

The stereoselective direct transformation of N-(propargylic)hydroxylamines into cis-2-acylaziridines was achieved by the combined use of AgBF4 and CuCl. Copper salts were found to promote the transformation of the intermediary 4-isoxazolines into 2-acylaziridines and both 3-aryl- and 3-alkyl-substituted 2-acylaziridines could be prepared by using this method. Furthermore, subsequent 1,3-dipolar cycloaddition of azomethine ylides that were generated in situ from the intermediary 2-acylaziridines with maleimides was achieved in a stereoselective one-pot procedure to afford the corresponding 2-acylpyrrolidines, which consisted of an octahydropyrrolo[3,4-c]pyrrole skeleton. Love the way ylide: The transformation of N-(propargylic) hydroxylamines into cis-2-acylaziridines and subsequent 1,3-dipolar cycloaddition of the in situ generated azomethine ylides with maleimides stereoselectively afforded 2-acylpyrrolidines. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Desymmetrization of 1,4-pentadien-3-ol by the asymmetric 1,3-dipolar cycloaddition of azomethine imines

Desymmetrization of the divinyl carbinol 1,4-pentadien-3-ol was accomplished by the asymmetric 1,3-dipolar cycloaddition of azomethine imines based on a magnesium-mediated, multinucleating chiral reaction system utilizing diisopropyl (R,R)-tartrate as the chiral auxiliary. The corresponding optically active trans-pyrazolidines, each with three contiguous stereogenic centers, were obtained with excellent regio-, diastereo-, and enantioselectivity, with results as high as 99 %ee. This reaction was shown to be applicable to both aryl- and alkyl-substituted azomethine imines. The use of a catalytic amount of diisopropyl (R,R)-tartrate was also effective when accompanied by the addition of MgBr2. © 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Synthesis of 3,6-Dihydro-2H-1,2-oxazines via Dimethylsulfoxonium Methylide Addition to α,β-Unsaturated Nitrones

金沢大学理工学研究域物質化学系A unique and efficient formation of 3,6-dihydro-2H-1,2-oxazines starting from α,β-unsaturated nitrones has been achieved. The nucleophilic addition of dimethylsulfoxonium methylide to the C═N bond of an α,β-unsaturated nitrone to form an aziridine N-oxide followed by the Meisenheimer rearrangement affords 3,6-dihydro-2H-1,2-oxazine in up to 70% yield. Methylene was confirmed to be incorporated at the C3 position of the ring. A wide range of β-aryl-substituted α,β-unsaturated nitrones were applicable to this reaction.Embargo Period 12 month

Formal Methylene Insertion into the C–H Bond of α-Carbonyl Aldonitrones with Dimethylsulfoxonium Methylide

金沢大学理工学研究域物質化学系A methylene group was introduced into the C–H bond of α-carbonyl aldonitrones by reaction with dimethylsulfoxonium methylide, producing one-carbon homologated C-methyl ketonitrones. This formal methylene insertion was applied to one-pot synthesis of quaternary C3-methyl isoxazolidines via successive 1,3-dipolar cycloaddition with alkenes bearing an electron withdrawing group