66628-94-2Relevant academic research and scientific papers
Cu(I)-catalyzed, α-selective, allylic alkylation reactions between phosphorothioate esters and organomagnesium reagents
Lauer, Andrew M.,Mahmud, Farzeen,Wu, Jimmy
, p. 9119 - 9123 (2011/08/04)
Regiocontrol of allylic alkylation reactions involving hard nucleophiles remains a significant challenge and continues to be an active area of research. The lack of general methods in which α-alkylation is favored underscores the need for the development of new processes for achieving this type of selectivity. We report that Cu(I) catalyzes the allylic substitution of phosphorothioate esters with excellent α-regioselectivity, regardless of the nature of the Grignard reagent that is used. To the best of our knowledge, the Cu-catalyzed allylic alkylation of phosphorothioate esters has never been described. We have also developed a simple protocol for inducing high α selectivity starting from secondary allylic halides. This is accomplished by using sodium phosphorothioates as an additive.
Reaction of Phenyl-Substituted Allyllithiums with tert-Alkyl Bromides. Remarkable Difference in the Alkylation Regiochemistry between a Polar Process and the One Involving Single-Electron Transfer
Tanaka, Jiro,Nojima, Masatomo,Kusabayashi, Shigekazu
, p. 3391 - 3397 (2007/10/02)
The reaction of phenyl-substituted allyllithiums 1a-h with tert-alkyl bromides was investigated systematically.The alkylation regiochemistry was influenced in a complicated fashion by various factors including substituent effects, both steric and electronic, solvents, and the presence of strongly coordinating additives, tetramethylethylenediamine and hexamethylphosphoramide.On the basis of the cyclizable probe experiments, the observed regiochemistry was interpreted as follows. (a) The reaction proceeds by two alternative pathways, a polar one and single electron transfer (SET), the extent of each path being influenced by the variable factors and (b) a polar pathway favors coupling at the phenyl-substituted site (C-1), while in the case of SET the C-C bond formation occurs predominantly at the site far from the phenyl substituent (C-3).
Alkylation of Allylic Derivatives. 11. Copper(I)-Catalyzed Cross Coupling of Allylic Carboxylates with Grignard Reagents
Tseng, Chung Chyi,Paisley, Steven D.,Goering, Harlan L.
, p. 2884 - 2891 (2007/10/02)
Reactions of allylic carboxylates with Grignard reagents containing catalytic amounts (1-10 mol percent) of cuprous salts give high yields of cross-coupled products.With alkyl Grignard reagents, regiochemistry can be controlled by choice of cuprous salt.With cuprous halides, little regiospecificity is observed.There is a small excess of γ-coupling in unbiased systems such as 5-methyl-2-cyclohexenyl (1), 2-cyclohexenyl (3), and β-phenylallyl (5) carboxylates.With CuCN, complete regiospecificity (exclusive γ-coupling) is observed with all alkyl Grignard reagents in unbiased systems, and with n-butylmagnesium halide >97percent γ-coupling results with α-methyl-γ-phenylallyl pivalate (7-OPiv) which is biased in favour of coupling at the α-position.In sharp contrast to alkyl Grignard reagents, phenyl and vinyl Grignard reagents containing CuCN show no regiospecificity.
PHOTOCHEMISTRY OF β,γ-UNSATURATED KETONES - V ; THE DIRECT IRRADIATION OF SOME γ-PHENYL β;γ-ENONES
Weerdt, Anton J. A. Van Der,Cerfontain, Hans
, p. 2121 - 2130 (2007/10/02)
The photochemistry of some members of the two series of γ-phenyl substituted acyclic β,γ-unsaturated ketones 1 and 2 upon direct irradiation with λ 310 nm has been investigated, viz 1c-1h and 2b+2c.The alkyl substituted (E)-5-phenyl-4-penten-2-ones 1c-1h yield the corresponding 1,3-acyl shift products and (Z)-isomers, and 1g and 1h in addition two decarbonylated products. 2b only yields the (Z)-isomer and some benzaldehyde, but 2c yields the 1,3-acyl shift product, the ODPM product, three hydrocarbons formed by disproportionation of the allyl radical, and some benzaldehyde.The β-phenyl β,γ-UK 3a proved to be photostable.The 1,3-acyl shift products of 1c-1h result mainly from the singlet excited state in a cage radical process.The exclusive formation of the (E)-configuration of the 1,3-acyl shift product is explained in terms of conformational preference of the intermediate allyl radical.It is proposed that the formation of the (Z)-isomer proceeds from 1T(?-?*) which is populated according to .Evidence is presented which supports the proposed mechanism.The β,γ-UK 2b containing a benzoyl moiety leads to a higher degree of (E)-(Z) isomerization than the corresponding 1d which has an acetyl moiety.The triplet energies of (E)- and (Z)-1h are 56 and ca 70 kcal/mol respectively.
