ASYMMETRIC HYDROFORMYLATION OF HETEROCYCLIC OLEFINS CATALYZED BY CHIRAL PHOSPHINE-PHOSPHITE-RH(I) COMPLEXES

Asymmetric hydroformylation of heterocyclic olefins catalyzed by phosp hine-phosphite-Rh(I) complexes has been investigated. Hydroformylation of symmetrical heterocyclic olefins such as 2,5-dihydrofuran, 3-pyrro line derivatives, and 4,7-dihydro-1,3-dioxepin derivatives afforded th e optically active aldehydes as single products in 64-76% ee. Unsymmet rical substrates such as 2,3-dihydrofuran and N-(tert-butoxycarbonyl)- 2-pyrroline gave a mixture of regioisomers. From N-(tert-butoxycarbony l)-2-pyrroline was obtained N-(tert-butoxycarbonyl)pyrrolidine-2-carba ldehyde in 97% ee. The hydroformylation products from 2,5-dihydrofuran and N-(tert-butoxycarbonyl)-3-pyrroline have the opposite configurati ons to those from 2,3-dihydrofuran and N-(tert-butoxycarbonyl)-2-pyrro line, respectively, with the same catalyst. The new phosphine-phosphit e ligand (R,S)-3,3'-Me-2-BINAPHOS [= (R)-2-(diphenylphosphino)-1,1'-bi naphthalen-2'-yl (S)-3,3'-dimethyl-1,1'-binaphthalene-2,2'-diyl phosph ite] was prepared and its hydridorhodium complex was characterized by NMR spectroscopy. Using (R,S)-3,3'-Me-2-BINAPHOS asa ligand, the enant ioselectivity was improved for some substrates. In addition, higher ca talytic activity was observed with this ligand for most of the substra tes employed.