A novel chromium-promoted alkyl- and silyl cyclopropanation of (E)- or (Z)-alpha,beta-unsaturated amides in which the C-C double bond is di-, or trisubstituted is described. This process takes place with total stereospecificity, and the new stereogenic center is generated with high or total stereoselectivity. A mechanism is proposed to explain the cyclopropanation reaction.

We describe herein a CrCl(2)-promoted cyclopropanation of alpha,beta-unsaturated amides. This reaction can be carried out on (E)- or (Z)-alpha,beta-enamides in which the C-C double bond is di-, tri-, or tetrasubstituted. In all cases the process is completely stereospecific and only a single diastereoisomer is obtained. In addition, cyclopropyl ketones were readily prepared by reaction of the cyclopropanecarboxamides (derived from morpholine) obtained with a range of organolithium compounds. A mechanism has been proposed to explain the cyclopropanation reaction.

A convenient highly stereoselective synthesis of chloro-and bromocyclopropanamides from di-tri-or tetrasubstituted (E)-or (Z)-a,b-unsaturated amides with total or high stereoselectivity promoted by chromium dichloride or dibromide is described. The transformation of chlorocyclopropan-A C H T U N G T R E N N U N G amides into the corresponding ketones or amines is also reported. A mechanism to explain these transformations is proposed.

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A catalytic chromium-mediated novel synthesis of iodocyclopropanecarboxamides is reported. This reaction can be carried out on aromatic (E)-or (Z)-a,b-unsaturated amides in which the C=C double bond is di-or trisubstituted. This process takes place with total stereospecificity and the new C À I stereogenic center is generated with high stereoselectivity. Some synthetic applications of the obtained iodocyclopropanecarboxamides are also reported. The structures of the iodocyclopropanes and derivatives were established by X-ray analysis.