- Nickel-Catalyzed Alkylation or Reduction of Allylic Alcohols with Alkyl Grignard Reagents
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By choosing different phosphine ligands, nickel-catalyzed selective alkylation and reduction of allylic alcohols with alkyl Grignard reagents were performed. The reaction using Ni(dppe)Cl2 as the catalyst resulted in the cross-coupling of allylic alcohols with primary alkyl Grignard reagents and cyclopropylmagnesium bromide. The reaction catalyzed by the combination of Ni(PCy3)2Cl2 and dcype led to the reduction of allylic alcohols. Secondary alkyl Grignard reagents except cyclopropylmagnesium bromide always led to reduction of allylic alcohols using either Ni(dppe)Cl2 or Ni(PCy3)2Cl2/dcype as the catalyst. In the reductive reaction β-H-containing alkyl Grignard reagents were required.
- Yang, Bo,Wang, Zhong-Xia
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p. 4772 - 4784
(2020/05/01)
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- Stereodivergent synthesis of alkenes by controllable syn-/anti-fragmentation of β-hydroxysulfonyl intermediates
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The reduction of the carbonyl group in acylated trifluoroethyl alkanesulfonates follows the Felkin-Ahn selectivity, and the so-formed diastereomeric β-hydroxysulfonyl intermediates undergo syn- and anti-fragmentation, depending on the reaction conditions. In effect, isomeric E- and Z-alkenes are formed in a stereodivergent manner, which mimics the mechanistic manifold of the Peterson olefination.
- Górski, Bartosz,Basiak, Dariusz,Grzesiński, ?ukasz,Barbasiewicz, Micha?
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p. 7660 - 7663
(2019/08/30)
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- Olefination with Sulfonyl Halides and Esters: E-Selective Synthesis of Alkenes from Semistabilized Carbanion Precursors
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Carbanions of sulfonyl halides and activated sulfonates add to carbonyl compounds, and so-formed aldol-type adducts spontaneously fragment into olefins. This transformation mimics the one-pot Julia olefination with (hetero)aryl sulfones, but the mechanism of fragmentation involves a four-membered intermediate, typical for reactivity of phosphorus reagents. Moreover, in contrast to the reactions of sulfones, sulfonates of fluorinated alcohols (TFE and HFI) produce byproducts that are easily removed during workup. In our report, we focus on reactions of unstabilized and semistabilized carbanion precursors: alkylsulfonates, and allyl- and benzylsulfonates, respectively. In particular for semistabilized systems, olefins were synthesized as predominant E isomers in good yields. The presented studies reveal that optimal reaction conditions, including the type of base and alcohol groups of the sulfonates, are different depending on stabilization of the carbanion precursors and structure of the carbonyl substrates. The practical synthetic guide is supplemented with a discussion of the mechanism, based on reactivity studies of intermediates and identification of side-products.
- Górski, Bartosz,Basiak, Dariusz,Talko, Alicja,Basak, Tymoteusz,Mazurek, Tomasz,Barbasiewicz, Micha?
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supporting information
p. 1774 - 1784
(2018/04/27)
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- TRANSITION METHAL-CATALYZED SUBSTITUTION REACTION OF ALLYLIC PHOSPHATES WITH GRIGNARD REAGENTS
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SN2-selective Grignard coupling with primary allylic diphenylphosphates was successfully achieved using Ni or Fe catalyst.In sharp contrast, a catalytic amount of CuCN*2LiCl promoted a SN2'-selective coupling reaction.In the presence of the copper catalyst, stereochemically homogeneous γ-disubstituted allyl Grignard reagents reacted at the less substituted allylic terminus (α-position) with an allylic diphenylphosphate selectively without losing the double bond geometry.
- Yanagisawa, Akira,Nomura, Nobuyoshi,Yamamoto, Hisashi
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p. 6017 - 6028
(2007/10/02)
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- The invention of radical reactions. Part XXVII. Modified Julia synthesis of olefins using radical deoxygenation
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Xanthate derivatives of β-hydroxy sulfones react with methyl radicals generated from the photolysis of N-acetyloxy-2-thiopyridone to give the corresponding olefin. Under identical conditions a secondary alcohol is transformed into its thiopyridyl derivative.
- Barton, Derek H. R.,Tachdjian, Catherine
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p. 7109 - 7120
(2007/10/02)
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- Olefin synthesis by radical methods for xanthate, selenobenzoate and thionocarbonate derivatives of β-hydroxy sulfones
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β-Hydroxy sulfones have heen transformed to the corresponding radicophilic derivatives (xanthates selenobenzoates, thionocarbonates). These compounds can then be employed in the synthesis of the corresponding olefins by radical methods without the use of
- Barton,Jaszberenyi,Tachdjian
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p. 2703 - 2706
(2007/10/02)
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