- Steric parameters in the Ir-catalyzed regio- and diastereoselective isomerization of primary allylic alcohols
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The iridium-catalyzed diastereo- and regioselective isomerization of primary allylic alcohols using Crabtree's catalyst or sterically modified analogs is reported. The importance of the size of the substituents on either the substrates or the catalysts has been rationalized by linear free energy relationships.
- Li, Houhua,Mazet, Clement
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supporting information
p. 6170 - 6173
(2014/01/17)
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- The Diastereoselectivity of Electrophilic Attack on Trigonal Carbon Adjacent to a Stereogenic Centre: Diastereoselective Alkylation and Protonation of Open-chain Enolates having a Stereogenic Centre at the β Position
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Methylation of the enolates 7, 24, 28 and 33 and protonation of the enolates 10, 27, 31 and 36 are diastereoselective in conformity to a general rule, summarised in the drawing 1, governing the stereochemistry of electrophilic attack on a double bond adjacent to a stereogenic centre.The sense of the selectivity is, with one exception, opposite to that of the corresponding nucleophilic attack on a carbonyl group adjacent to a stereogenic centre, which, with the same exception, follows Cram's and the Felkin-Anh rule, summarised in the drawing 2.The exception is probably the reduction 40 -> 38 + 39, with 39 as the major product.This result is inconsistent with Cram's and the Felkin-Anh rule if the isopropyl group is counted as 'larger' than the phenyl group, whereas the Grignard reaction 37 -> 38 + 39, where 39 is again the major product, and the corresponding electrophilic reactions 33 -> 34 + 35, with 34 as the major product, and 36 -> 34 + 35, with 35 as the major product, are all consistent with isopropyl being effectively larger than phenyl.
- Fleming, Ian,Lewis, Jeremy J.
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p. 3257 - 3266
(2007/10/02)
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- Solid-Liquid Phase-Transfer Catalysis without Solvent: Selective Mono- and Di-alkylation of Benzyl Methyl Ketone
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The alkylation of benzyl methyl ketone 1 has been performed by phase-transfer catalysis without solvent.Excellent yields of mono- 2 and di-alkyl derivatives 3 and 4 were obtained through general, selective and mild conditions.
- Aranda, Alfonso,Diaz, Angel,Diez-Barra, Enrique,Hoz, Antonio de la,Moreno, Andres,Sanchez-Verdu, Prado
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p. 2427 - 2430
(2007/10/02)
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- Formation and Reactions of 1-Phenyl-2-propanone Dianion and Related Systems with Electrophilic Reagents
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1-Phenyl-2-propanone, 1,1-diphenyl-2-propanone, and 1-(4-methoxyphenyl)-2-propanone were converted to their dicarbanions 3, 4, and 31, respectively, and their reactions with a number of electrophilic reagents were examined.All three dianions gave a mixture of C-1 and C-3 alkylation products when treated with alkyl halides of higher reactivity, while only C-1 alkylations occurred when alkyl halides of lower reactivity were used.It was also found that the 1,1-diphenyl-2-propanone and the 1-(4-methoxyphenyl)-2-propanone dianions 4 and 31 gave a higher ratio of C-1/C-3 alkylation products than the 1-phenyl-2-propanone dianion 3.When dianion 3 was reacted with p-anisaldehyde and a number of protonating agents, electrophilic attack occurred exclusively at the C-3 position.The trends observed are analyzed, and mechanisms are proposed to account for the results obtained.
- Trimitsis, G. B.,Hinkley, J. M.,TenBrink, R.,Faburada, A. L.,Anderson, R.,et al.
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p. 2957 - 2962
(2007/10/02)
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