New Ferrocenyloxazoline for the Preparation of Ferrocenes with Planar Chirality

Abstract

New ferrocenyloxazolines with two stereogenic centers were prepared with excellent yields starting from the (1S,2S)-(+)-2-amino-3-phenyl-1,3-propanediol. They can then be used for the preparation of ferrocenes with planar chirality with very high diastereoselectivities (>99:1%) by a lithiation/electrophile-trapping sequence. The syntheses of chiral (phosphinoferrocenyl)oxazoline and (phenylthioferrocenyl)oxazoline and their use as ligands in conjunction with bis[(π-allyl)palladium chloride] in the enantioselective allylic alkylation of rac-1,3-diphenylprop-2-enyl acetate was investigated.

1,2‐P,N‐Bidentate Ferrocenyl Ligands

“…Ferrocene-substituted PHOX 7b and homoannularly bridged ferrocene 58 also gave high ees in the reaction (entries 6 and 7) [55]. Introducing an additional chiral center at the substituent on the oxazoline ring of Fc-PHOX produced a new type of ligand 59, the reaction using it as ligand provided the product in high ee as well (entry 8) [56]. Pyrazole-containing ferrocenyl phosphine ligands 5 developed by Togni demonstrated their excellent asymmetric induction in the amination reaction.…”

The Development of Bidentate P,N Ligands for Asymmetric Catalysis

“…[118] Subsequently, iridium and ruthenium complexes of the parent ligands 310 ± 315 were found to be effective catalysts for the reduction of a range of both ketone and imine substrates. [119] Other derivatives such as 317 ± 319, [120] 320 [121] and 321 [122] have been prepared and tested in the allylic alkylation of 1,3-diphenyl-2-propenyl acetate (15), Table 32. It should be noted that ligands 317 ± 319 do not possess planar chirality but, similar to ligands 108 ± 114, form an axially chiral system when complexed to a metal.…”

New Ferrocenyl Phenol Thiophosphines

“…These ligands bear one phosphino group and one other coordination site [2] like a sulfur atom [3], a phosphorus atom [4], a nitrogen atom [5], an Nheterocyclic carbene [6], an oxygen atom [7] ,…. These ligands have been used in various catalytic asymmetric reactions, like asymmetric allylic substitution, asymmetric alkoxycarbonylation, asymmetric hydrogenation, asymmetric Suzuki-Miyaura coupling [2][3][4][5][6][7][8][9],… Most of these ligands have been synthesized from a common intermediate: the alcohol 1(see Scheme 1) which can be efficiently synthesized as racemic mixture or in an enantiomerically pure form [2].…”