Diastereoselective deprotonative metalation of chiral ferrocene derived acetals and esters using mixed lithium-cadmium and lithium-zinc combinations - Université de Rennes Accéder directement au contenu
Article Dans Une Revue Tetrahedron Année : 2014

Diastereoselective deprotonative metalation of chiral ferrocene derived acetals and esters using mixed lithium-cadmium and lithium-zinc combinations

Résumé

In situ bimetal combinations, and notably those prepared from MCl2(radical dotTMEDA) (M=Zn, Cd; TMEDA=N,N,N′,N′-tetramethylethylenediamine) and Li(TMP) (3 or 4 equiv, TMP=2,2,6,6-tetramethylpiperidino), were screened for their ability to diastereoselectively deprotonate ferrocenes bearing a chiral group. The ferrocene carboxylate generated from diacetone-d-glucose afforded the corresponding 2-iodo derivative in 74% yield with 90% de (SP diastereoisomer) using the base generated from CdCl2 and Li(TMP) (3 equiv), and in 85% yield with 91% de (SP diastereoisomer) through a double asymmetric induction using a chiral lithium-zinc base generated from ZnCl2*TMEDA and lithium (R)-bis(1-phenylethyl)amide (4 equiv). In contrast, using a combination prepared from ZnCl2 and Li(TMP) (4 equiv) with the ferrocene carboxylate obtained from 6-(tert-butoxycarbonylamino)-6-deoxy-3-O-methyl-1,2-O-isopropylidene-α-d-glucofuranose led to the RP-iodo derivative in 57% yield after separation. Suzuki coupling was performed satisfactorily on the isolated SP and RP diastereoisomer iodoesters.
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Dates et versions

hal-00993136 , version 1 (20-05-2014)

Identifiants

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Gandrath Dayaker, Aare Sreeshailam, D. Venkata Ramana, Floris Chevallier, Thierry Roisnel, et al.. Diastereoselective deprotonative metalation of chiral ferrocene derived acetals and esters using mixed lithium-cadmium and lithium-zinc combinations. Tetrahedron, 2014, 70 (12), pp.2102-2117. ⟨10.1016/j.tet.2014.02.010⟩. ⟨hal-00993136⟩
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