Development of Conjugate Addition of Lithium Dialkylcuprates to Thiochromones: Synthesis of 2-Alkylthiochroman-4-ones and Additional Synthetic Applications
Lithium dialkylcuprates undergo conjugateaddition to thiochromones to afford 2-alkylthiochroman-4-ones in good yields. This approach provide an efficient and general synthetic approach to privileged sulfur-containing structural motifs and valuable precursors for many pharmaceuticals, starting from common substrates-thiochromones. Good yields of 2-alkyl-substituted thiochroman-4-ones are attained with
Synthesis of Enantiomerically Pure β- and γ-Amino Acids from Aspartic and Glutamic Acid Derivatives
作者:A. El Marini、M. L. Roumestant、Ph. Viallefont、D. Razafindramboa、M. Bonato、M. Follet
DOI:10.1055/s-1992-26315
日期:——
An efficient synthesis of enantiomerically pure β- and γ-amino acids starting from commercially available aspartic and glutamic acid derivatives is described. The acid function, α to the amino group, is first transformed to a good leaving group and the product reacted with organocuprates to yield β-and γ-amino esters. After deprotection β- and γ-amino acids are obtained in good overall yields.
Allenes. Part XXVII. Reaction of dialkyl(lithio)copper reagents with 1-bromoallenes, 1-iodoallenes, and 3-chloroalk-1-ynes
作者:Michael Kalli、Phyllis D. Landor、Stephen R. Landor
DOI:10.1039/p19730001347
日期:——
Allenichydrocarbons are obtained in high yield by the reaction of 1-halogenoallenes or 3-chloroalk-1-ynes with dialkyl(lithio)copper reagents at low temperature.
Trialkylsilyl chlorides, particularly in combination with hexamethylphosphoramide or 4-dimethylaminopyridine, dramatically accelerates the conjugate addition of catalytic and stoichiometric organocopperreagents onto enones, enals, and enoates, in which very high degrees of stereo- and chemoselectivities were observed.
In order to evaluate the electron transfer ability of organocopperreagents, the reactions of appropriate Michael acceptors with methyl- and butylcopper reagents were investigated. The reaction of trimethyl ethylene-1,1,2-tricarboxylate (1a) with methylcopper reagents gave a mixture of the conjugate adduct 2a and reduction product 3a in good to high yields. The ratio of 2a and 3a varied with the copper