Rh and Pd-catalysed Reactions of Diazo Compounds via Electrophilic Carbene Complexes

5 Rh and Pd-catalysed Reactions of Diazo Compounds via Electrophilic Carbene Complexes 

Well-known is the cyclopropanation of various alkenes. As shown by 329, cyclopropanation starts by electrophilic attack to the alkene. Electron-rich alkenes have higher reactivity. Numerous applications of intramolecular cyclopropanation to syntheses of natural products have been reported. Optically active cyclopropanes are prepared by enantioselective cyclopropanation [100], As the first successful example, asymmetric synthesis of chrysanthemic acid (331) was carried out by cyclopropanation of 2,5-dimethyl-2,4-hexadiene (330) with diazoacetate, catalysed by the chiral 

4-Cycloheptadiene (340) is obtained by the Cope rearrangement of cis-divinylcyclopropane (339.) Based on this reaction, highly diastereoselective and enantioselective construction of the 1,4-cycloheptadiene 343 (98% ee) was achieved by domino asymmetric cyclopropanation to generate cA-divinylcyclopropane 

Synthetic reactions via transition metal carbene complexes 

Pd(OAc)2 catalyses cyclopropanation of terminal alkene or a,/ -unsaturated enones [109]. Selective cyclopropanation of the terminal alkene in the macrolactam 344 gives 345 in high yield [110], 

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