Cyclopropylamines are successfully synthesized by the reaction of different substituted carboxamides with Grignard reagents in the presence of stoichiometric amounts of Me-Ti(O-iPr)3. The present new method is applicable to N,N-dialkyl-and N-alkyl--N-phosphorylalkyl-substituted carboxamides (I) as well as optically active substrates. Using substituted Grignard reagents (VI) or oxygen-functionalized Grignard reagents (VIII), products are obtained as a mixture of cis-and trans-isomers favoring trans-isomers albeit with moderate diastereoselectivity. Under similar conditions dicyclopropylamines (XIV) and cyclopropanol (XVI) are formed. Furthermore, the preparation of sterically demanding cyclopropylamine (XVIII) is achieved using Ti(O-iPr) 4 . For the asymmetric reaction of (I) with (VIa), a chiral titanium/ TADDOL complex is used. The method can also be employed for the synthesis of several bioactive compounds as is shown for spirocyclopropane (XXI) which is a cotinine derivative. -(DE MEIJERE*, A.; CHAPLINSKI, V.; WINSEL, H.; KORDES, M.; STECKER, B.; GAZIZOVA, V.; SAVCHENKO, A. I.; BOESE, R.; SCHILL, F.; Chem. Eur. J. 16 (2010) 46, 13862-13875, http://dx.
2000organo-silicon compounds, isocyclic C derivatives organo-silicon compounds, isocyclic C derivatives S 0064
-184Silyl Effect on the Regioselective Synthesis of Silylated Alkylidenecyclopropanes.-Nucleophilic substitution of silylated cyclopropanes of type (I) is found to occur on the carbon bearing the silyl group. However, the reaction of analogues in which the silyl group is located on the ring with hard nucleophiles takes place on the ring, whereas with soft nucleophiles the vinyl group is attacked. Starting from disilylated derivatives like (X) no ring attack is observed, indicating that the effect of the vinyl silyl group dominates. Electrophilic substitution of silanes of type (XII) by Ph-CHO occurs regioselectively on the cyclopropane ring.
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