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Stereospecific Cyclopropanation of Highly Substituted C-C Double Bonds Promoted by CrCl2. Stereoselective Synthesis of Cyclopropanecarboxamides and Cyclopropyl Ketones
文摘
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We describe herein a CrC
l2-promoted cyc
lopropanation of
lpha.gif" BORDER=0>,
le">-unsaturated amides. This reaction can be carried out on (
E)- or (
Z)-
lpha.gif" BORDER=0>,
le">-enamidesin which the C-C doub
le bond is di-, tri-, or tetrasubstituted. In a
ll cases the process is comp
lete
ly stereospecific and on
ly a sing
le diastereoisomeris obtained. In addition, cyc
lopropy
l ketones were readi
ly prepared by reaction of the cyc
lopropanecarboxamides (derived from morpho
line)obtained with a range of organo
lithium compounds. A mechanism has been proposed to exp
lain the cyc
lopropanation reaction.