- Expanding the scope of the Babler–Dauben oxidation: 1,3-oxidative transposition of secondary allylic alcohols
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We report the catalytic chromium-mediated oxidation of secondary allylic alcohols to give α,β-unsaturated aldehydes with exclusive (E)-stereoselectivity. This facile procedure employs catalytic PCC (5?mol?%) and periodic acid (H5IO6) as a co-oxidant. This transformation occurs specifically with aromatic substituted allyl alcohols containing both electron withdrawing and electron donating substituents as well as a range of functional groups.
- Killoran, Patrick M.,Rossington, Steven B.,Wilkinson, James A.,Hadfield, John A.
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supporting information
p. 3954 - 3957
(2016/08/09)
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- Zn(II)- or Ag(I)-catalyzed 1,4-metathesis reactions between 3-en-1-ynamides and nitrosoarenes
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Catalyst-dependent metathesis reactions between 3-en-1-ynamides and nitrosoarenes are described. Particularly notable are the unprecedented 1,4-metathesis reactions catalyzed by Ag(I) or Zn(II) to give 2-propynimidamides and benzaldehyde derivatives. With 3-en-1-ynamides bearing a cycloalkenyl group, 1,4-oxoimination products were produced efficiently. We have developed metathesis/alkynation cascades for unsubstituted 2-propynimidamides and benzaldehyde species generated in situ, to manifest 1,4-hydroxyimination reactions of 3-en-1-ynes. Both 1,4-oxoiminations and 1,4-hydroxyiminations increase the molecular complexity of products.
- Gawade, Sagar Ashok,Huple, Deepak B.,Liu, Rai-Shung
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p. 2978 - 2981
(2014/03/21)
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- A catalytic asymmetric bioorganic route to enantioenriched tetrahydro- and dihydropyranones
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A conceptually novel approach to hetero Diels-Alder adducts of carbonyl compounds is described using as the key steps an antibody-mediated kinetic resolution of hydroxyenones followed by a ring-closure process. Various β-hydroxyenones proved to be very good substrates for antibodies 84G3- and 93F3-catalyzed retro-aldol reactions, allowing the preparation of highly enantiomerically enriched (up to 99% ee) precursors of pyranones. An attractive feature of this methodology is the possibility to convert these acyclicenantioenriched β-hydroxyenones into tetrahydropyranones by a conventional Michael-type addition procedure or into the corresponding dihydropyranones using an alternative palladium-catalyzed oxidative ring closure. For the palladium-mediated cyclization, a biphasic system has been implemented that allows the direct preparation of enantiopure dihydropyranones from the corresponding racemic aldol precursors using a sequential antibody-resolution/palladium-cyclization strategy, without isolation of the intermediate enantioenriched hydroxyenones. This bioorganic route is best applied to the preparation of hetero Diels-Alder adducts otherwise derived from less nucleophilic dienes and unactivated dienophiles.
- Baker-Glenn, Charles,Hodnett, Neil,Reiter, Maud,Ropp, Sandrine,Ancliff, Rachael,Gouverneur, Veronique
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p. 1481 - 1486
(2007/10/03)
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- SELECTIVE REDUCTION OF ALDEHYDES TO THE CORRESPONDING PRIMARY ALCOHOLS BY LITHIUM ENOLATE OF ACETALDEHYDE
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Reaction of lithium enolate of acetaldehyde (obtained by cycloreversion of THF in the presence of n-BuLi) with a number of nonenolizable aldehydes (aromatic, heteroaromatic, cinnamaldehyde) in THF and room temperature affords good to quantitative yields of the corresponding primary alcohols, instead of other products commonly reported for similar conditions.Reduction of the carbonyl group is the main reaction even in the presence of other reducible groups or parts of the same group.A possible mechanism of reaction is also proposed.
- Nunno, L. Di.,Scilimati, A.
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p. 3639 - 3644
(2007/10/02)
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