5-alkylating of cyclopentadienes - by reaction of rare earth cyclopentadienides with alkyl halides, alkane- or arene-sulphonates

摘要

5-alkylation of cyclopentadienes by reaction of rare earth metal cyclopentadienides with a cpd. of formula RX where R is alkyl or the group -CH2.O.CH2R' where R' is H, opt. subst. alkyl, aryl or aralkyl; X is halogen, mesylate, tosylate or bromotosylate. Reactants are of low toxicity (cf. with T1) yields of =90% are achieved, only about 1-2% of isomer 1 is formed and the reaction time is than 1 hr. The pref. metal is 2a which gives table derivs. Reaction is pref. in ether, tetrahydrofuran or dimethoxyethane at -40 to -15 degrees C. The obtd. prods are used as inters in the synthesis of prostaglandins.