Enantioselective deprotometalation of alkyl ferrocenecarboxylates using bimetallic bases

Abstract

Our attempts to deprotometalate alkyl ferrocenecarboxylates enantioselectively by using chiral lithium–zinc or lithium–cadmium bases are reported.

Forever young: the first seventy years of ferrocene

“…Complementary synthetic methods (Scheme 13) were based on the metalation of suitable prochiral substrates bearing coordinating groups, such as tertiary amide 43 , 120 amine 36 121 and phosphine oxide 48 , 122 by adducts generated from organolithium compounds and chiral amines, such as (−)-sparteine ( 45 ) and (1 R ,2 R )- N , N , N ′, N ′-tetramethylcyclohexane-1,2-diamine ( 47 ), or, alternatively, by chiral amides. 123…”

Exploring the boundaries of ferrocenesulfonyl fluoride chemistry

“…This was demonstrated by Price and Simpkins who reported the asymmetric deprotolithiation of P,Pdiphenylferrocenephosphine oxide in 54% ee by using lithium bis[(S)-1-phenylethyl]amide [(S)-PEALi] in the presence of trimethylsilyl chloride as an in situ trap. 66 We recently demonstrated that the use of more efficient chiral zinc-based in situ traps could be beneficial for some substrates and managed to reach enantioenriched N,N-dialkylferrocenecarboxamides, 67 O-alkylferrocenecarboxylates 68 and Oisopropylferrocenesulfonate 55 with ee ranging from 64 to 80%. Here, we initially evaluated the use of alkyllithium•chiral diamine chelates to perform the enantioselective deprotolithiation of the substrate 2 before adding a suitable electrophile.…”