Asymmetric allylic substitutions on symmetrical and non-symmetrical substrates using [5]ferrocenophane ligands

A series of [5]ferrocenophane diphosphane ligands were used in Pd-catalyzed allylic substitution reactions. With a symmetrical substrate, 1,3-diphenylpropenyl acetate, enantioselectivities between 70% and 94% ee were observed. Several non-symmetrically substituted allylic substrates were also used. Depending on the substituents of the non-symmetrical allylic substrates, various degrees of regioselectivity (from 1:1 to 100:0) and enantioselectivity (from 0% to 96% ee) were observed. Tentative catalytically active complexes were studied by DFT computational methods.

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(R,Sp)-1-(Diphenylphosphanyl)-2,1′-[1-(dicyclohexylphosphanyl)pentan-1,5-diyl]ferrocene, bis(borane) complexC39H54B2FeP2[α]D = −388 (c 0.13, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (R,Sp)

(R,Sp)-1-(Diphenylphosphanyl)-2,1′-[1-(di-(3,5-dimethylphenyl)phosphanyl)pentan-1,5-diyl]ferrocene, bis(borane) complexC43H50B2FeP2[α]D = −378 (c 0.11, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (R,Sp)

(R,Sp)-1-(Diphenylphosphanyl)-2,1′-[1-(di-tert-butylphosphanyl)pentan-1,5-diyl]ferrocene, bis(borane) complexC35H50B2FeP2[α]D = −375 (c 0.25, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (R,Sp)

Dimethyl 2-(4,4-dimethyl-1-phenylpent-2-enyl)malonateC18H24O4[α]D = +60.2 (c 0.41, CHCl3), for 85% eeSource of chirality: asymmetric synthesisAbsolute configuration: unknown

(S)-Dimethyl 2-(1,3-diphenylallyl)malonateC20H20O4[α]D = −14.2 (c 0.7, CHCl3) for 90% eeSource of chirality: asymmetric synthesisAbsolute configuration: (S)