Design and development of new, catalytic carbon-carbon bond forming reactions using zirconium and nickel
Abstract
Key mechanistic features of the Zr-catalyzed carbomagnesation are illustrated below. Addition of EtMgCl to I leads to the formation of the derived zirconate II which undergoes site-selective cleavage, due to chelation of magnesium with the neighboring Lewis basic alkoxide (III to IV). Subsequent $/beta$-hydride abstraction followed by reductive elimination regenerates the catalyst (V) and provides the alkylmagnesium VI which is then trapped by an electrophile (e.g., O$/sb2$) to afford VII.
Catalytic asymmetric synthesis. 2,5-Dihydrofuran in equation 1 undergoes highly enantioselective ethylmagnesation (97% enantiopurity).
Catalytic kinetic resolution. As exemplified below, subjection of a racemic mixture of pyrans to asymmetric carbometallation conditions affords efficient and facile kinetic resolution. Similar results have been obtained for pyrans with a variety of substitution patterns.
Ni-catalyzed alkylations. We have been investigating a phosphine directed Ni-catalyzed addition of Grignard reagents to allylic ethers. The Lewis basic phosphine is necessary for reactivity and selectivity (eq 3). An example shown below is representative.* ftn*Please refer to the dissertation for diagrams.
Subject Area
CHEMISTRY, ORGANIC (0490)
Recommended Citation
Mary T Didiuk,
"Design and development of new, catalytic carbon-carbon bond forming reactions using zirconium and nickel"
(January 1, 1996).
Boston College Dissertations and Theses.
Paper AAI9707875.
http://escholarship.bc.edu/dissertations/AAI9707875
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