Direct formation of highly functionalized allylic organocopper reagents from allylic chlorides and acetates
作者:Douglas E. Stack、Bryan T. Dawson、Reuben D. Rieke
DOI:10.1021/ja00039a023
日期:1992.6
The direct formation of highly functionalized allylic organocopper reagents has been carried out using a highly active form of zerovalent copper (Cu*). The cold-temperature reduction of CuCN.nLiX complexes by lithium naphthalenide in THF under an argon atmosphere produces the Cu* complex, which reacts rapidly with primary and secondary allyl chlorides at −100°C with little homocoupling. Allyl, methallyl
The first direct preparation of allylbarium reagents by reaction of insitu generated reactive barium with various allylic chlorides and their new and unexpected selective allylation reactions with carbonyl compounds are disclosed. Highly reactive barium was readily prepared by the reduction of barium iodide with 2 equiv of lithium biphenylide in dry THF at room temperature. A variety of carbonyl compounds reacted with barium reagents generated from (E)- or (Z)-allylic chlorides in THF at -78 degrees C. All reactions resulted in high yields with remarkable alpha-selectivities not only with aldehydes but also with ketones. The double bond geometry of the starting allylic chloride was completely retained in each case. Stereochemically homogeneous (E)- and (Z)beta,gamma-unsaturated carboxylic acids were easily prepared in good yields by highly alpha-selective carboxylation of allylic barium reagents with carbon dioxide. A selective Michael addition reaction with alpha,beta-unsaturated cycloalkanone was also achieved using an allylbarium reagent. Treatment of 2-cyclopentenone (1 equiv) with allylbarium chloride (2 equiv) in THF at -78 degrees C for 20 min afforded 3-allylcyclopentanone in 94% yield with a 1,4/1,2 ratio of >99/1. Furthermore, the in situ generated barium enolate was efficiently trapped with various kinds of electrophiles (Me(2)C=CHCH2Br, (C5H11CHO)-C-n, and CH3COCl).
Lipshutz, Bruce H.; Ellsworth, Edmund L.; Dimock, Stuart H., Journal of the American Chemical Society, 1990, vol. 112, # 11, p. 4404 - 4410
作者:Lipshutz, Bruce H.、Ellsworth, Edmund L.、Dimock, Stuart H.、Smith, Robin A.J.
DOI:——
日期:——
Conjugate Addition Reactions of Allylic Copper Species Derived from Grignard Reagents: Synthetic and Spectroscopic Aspects
作者:Bruce H. Lipshutz、Claus Hackmann
DOI:10.1021/jo00103a042
日期:1994.12
A general study on the 1,4-addition chemistry of allyl, methallyl, crotyl, and prenyl Grignard-derived organocopper reagents has been conducted. While diallylic cuprates formed from such species are not effective Michael donors, the 1:1:1 combination of an allylic Grignard, CuBr.SMe(2), and Me(3)SiCl leads to high yields of 1,4-adducts. The stereo- and regiochemistry associated with the allylic ligand, where appropriate, has also been examined. Low temperature C-13 NMR studies provide insight as to the nature of these complexes.
HIGHLY REACTIVE FORM OF COPPER AND REAGENTS THEREOF
申请人:Board of Regents of the University of Nebraska