- Rh-catalyzed aldehyde - Aldehyde cross-aldol reaction under base-free conditions: In situ aldehyde-derived enolate formation through orthogonal activation
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The chemoselective generation of aldehyde-derived enolates to realize an aldehyde - aldehyde cross-aldol reaction is described. A combined Rh/dippf system efficiently promoted the isomerization/aldol sequence by using primary allylic, homoallylic, and bishomoallylic alcohols; secondary allylic and homoallylic alcohols; and trialkoxyboranes that were derived from primary allylic and homoallylic alcohols. The reaction proceeded at ambient temperature under base-free conditions, thus giving cross-aldol products with high chemoselectivity. Mechanistic studies, as well as its application to double-aldol processes under protecting-group-free conditions, are also described. Copyright
- Lin, Luqing,Yamamoto, Kumiko,Matsunaga, Shigeki,Kanai, Motomu
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supporting information
p. 2974 - 2983
(2014/01/06)
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- Rhodium-catalyzed cross-aldol reaction: In situ aldehyde-enolate formation from allyloxyboranes and primary allylic alcohols
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Dip in. A Rh/dippf catalyst generates aldehyde-derived enol boranes at ambient temperature by isomerization of allyloxy- and homoallyloxyboranes. A one-pot isomerization/cross-aldol sequence provides aldehyde-aldehyde adducts in good yield with syn select
- Lin, Luqing,Yamamoto, Kumiko,Matsunaga, Shigeki,Kanai, Motomu
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supporting information
p. 10275 - 10279,5
(2012/12/12)
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- Rhodium-catalyzed cross-aldol reaction: In situ aldehyde-enolate formation from allyloxyboranes and primary allylic alcohols
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Dip in! A Rh/dippf catalyst generates aldehyde-derived enol boranes at ambient temperature by isomerization of allyloxy- and homoallyloxyboranes. A one-pot isomerization/cross-aldol sequence provides aldehyde-aldehyde adducts in good yield with syn select
- Lin, Luqing,Yamamoto, Kumiko,Matsunaga, Shigeki,Kanai, Motomu
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supporting information
p. 10275 - 10279
(2013/01/15)
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- Tandem olefin migration-aldol condensation in water with an amphiphilic resin-supported ruthenium complex
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A catalytic tandem olefin migration-aldol condensation process with allylic carbinols and aryl aldehydes was performed with 0.5 mol% of an amphiphilic polystyrene-poly(ethylene glycol) (PS-PEG) resin supported phosphine-ruthenium complex in water as a single reaction medium under heterogeneous conditions to give the corresponding aldols with syn selectivity. Inverse stereoselectivity (anti selectivity) was observed when the reaction was carried out in the presence of KO Georg Thieme Verlag Stuttgart.
- Oe, Yohei,Uozumi, Yasuhiro
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supporting information; experimental part
p. 787 - 790
(2011/06/21)
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- From allylic alcohols to aldols through a new nickel-mediated tandem reaction: Synthetic and mechanistic studies
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Nickel hydride type complexes have been successfully developed as catalysts for the tandem isomerization-aldolization reaction of allylic alcohols with aldehydes. Optimization of the reaction conditions has shown that a cocatalyst, such as MgBr2, has a very positive effect on the kinetics of the reaction and in the yields of aldols. Under such optimized conditions {[NiHCl(dppe)] + MgBr2 at 3-5 mol %)}, this reaction affords the aldols in good to excellent yields. It is a full-atom-economy-type reaction that occurs under mild conditions. Furthermore, it has a broad scope for the allylic alcohols and it is compatible with a wide range of aldehydes, including very bulky derivatives. The reaction is completely regioselective, but it exhibits a low stereoselectivity, except for allylic alcohols with a bulky substituent at the carbinol center. The use of chiral non-racemic catalysts was not successful, affording only racemic compounds. However, it was possible to use asymmetric synthesis for the preparation of optically active aldols. Various mechanistic studies have been performed using, for instance, a deuterated alcohol or a deuterated catalyst. They gave strong support to a mechanism involving first a transition-metal-mediated isomerization of the allylic alcohol into the free enol, followed by the addition of the latter intermediate onto the aldehyde in an "hydroxyl-carbonyl-ene" type reaction. These results confirm that allylic alcohols can be considered as new and useful partners in the development of the aldol reaction.
- Cuperly, David,Petrignet, Julien,Crevisy, Christophe,Gree, Rene
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p. 3261 - 3274
(2008/09/18)
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- From Allylic Alcohols to Aldols via a Novel, Efficient Reaction Catalyzed by Ni-Complexes
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Allylic alcohols react with aldehydes, in an atom economic aldol-type reaction, in the presence of a catalytic amount of (dppe)NiHCl/MgBr2 mixture. This reaction occurs in good to excellent yields with total regiocontrol and very high chemo control under mild conditions. It is compatible with various types of aldehydes including very bulky ones.
- Cuperly, David,Crévisy, Christophe,Grée, René
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- From allylic alcohols to aldols via a novel, tandem isomerization-condensation catalyzed by Fe(CO)5
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Allylic alcohols react with aldehydes, in the presence of catalytic amounts of Fe(CO)5 and under irradiation, to give mainly aldol products. A small amount of ketone resulting from the classical isomerization process is also isolated. This new aldol-type reaction is a complete atom economy process occurring under neutral conditions.
- Crévisy, Christophe,Wietrich, Marina,Le Boulaire, Virginie,Uma, Ramalinga,Grée, René
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p. 395 - 398
(2007/10/03)
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