THE MICHAEL INDUCED RAMBERG-BAECKLUND HOMOLOGATION TO CONJUGATED ISOPRENOIDS

Article abstract of DOI:10.1016/S0040-4020(01)92030-7

Treatment of the sulfones 1 or 2 with sodium phenylsulfinate in DMSO affords the head-to-tail coupled conjugated monoterpenoids 5-8 in comparable amounts.The correspondig reaction of 3 gives the isomers 16 and 17.The tail-to-tail homologation of 4 furnishes chiefly a 2E,4E/Z mixture of the conjugated isoprenoids 18 and 19.The various isoprenoid mixtures are separated into their components and the configuration of the isomers is established by (1)H NMR double resonance and the NMR/NOE technique.The head-to-tail and tail-to-tail coupled isoprenoid mixtures 5-8 and 18-21, respectively, are isomerized to 2E/Z,4E-mixtures in a 2:1 ratio.The C₁₅ sulfones 11 and 13 are obtained by treatment of 1 with the head-functionalized isoprene synthon 10.Some speculations on the stereochemical course of the MIRB-homologation are presented.