ChemInform Abstract: Synthesis and Stereoselective Reactions of α,β‐Unsaturated Acyl Ligands Bound to the Chiral Auxiliary ((η5‐C5H5)Fe(CO)(PPh3)): A Review

New chemical and stereochemical applications of organoiron complexes

“…For example, methoxycarbene complexes 24 are readily prepared by treatment of the bromide (22) with the appropriate lithium acetylide, to give (23), followed by protonation of the corresponding vinylidene complexes, and subsequent addition of methanol [ 179 – 181 ]. Alternatively, 24 may be obtained from the corresponding acyl complexes 25 [ 61 , 64 ] following treatment with trimethyloxonium tetrafluoroborate [ 182 ].…”

“…Triphenylphosphine-substituted analogues of the [(η 5 -C 5 H 5 )Fe(CO) 2 ] group, however, have emerged as very versatile intermediates for organic synthesis with potential applications in the area of asymmetric induction [ 41 , 286 , 287 , 293 ]. In regard to triphenylphosphine-substituted organoiron complexes including iron-carbene complexes such as [(η 5 -C 5 H 5 )Fe(CO)(PPh 3 ) = CHR + ] it was established [ 61 , 63 , 64 , 192 ] that the phosphine ligand (PPh 3 ) shields one face of the carbene moiety. Consequently reactions of iron-carbene complexes with nucleophiles can form two diastereomers.…”

“…Conjugate additions and conjugate addition-alkylations usually proceed with very high stereoselectivity to α, β-unsaturated acyls of [(η 5 -C 5 H 5 )Fe(CO)(PPh 3 )]. Here, Liebeskind [ 64 , 314 ] and Davies [ 61 , 62 , 311 , 324 ] are independently credited for the development of novel chiral reactions of the acetyl iron complex (94). It has been shown [ 64 , 314 ] that the enolate from (94), e.g., [(η 5 -C 5 H 5 )Fe(CO)(PPh 3 )COCH 2 ], reacts with aldehydes to afford aldol products 95 and 96 with high stereoselectivity ( Scheme 17 ).…”

“…To illustrate the generality of the new methodology for the synthesis of carbon-carbon double bonds [ 340 ], the Davies group [ 61 – 63 , 341 ] recently expanded the chiral auxiliary Michael-type reaction to include a series of aldehydes. Thus, starting with the chiral acetyl complex [(η 5 -C 5 H 5 )Fe(CO) (PPh 2 )COCH 3 ], the authors [ 341 ] generated, in high yields, E and Z α,β-unsaturated acyl complexes [(η 5 -C 5 H 5 )Fe (CO)(PPh 3 ) COCH = CHCH 3 ] by using the Peterson alkene synthesis reaction [ 342 ] between trimethylsilyl derivatives [(η 5 -C 5 H 5 )Fe(CO) (PPh 3 )COCH 2 Si(CH 3 ) 3 ] and aldehydes RCHO (R = H, CH 3 , Et, n-Bu, t-Bu, Ph, vinyl, 2-furyl).…”

“…Stereoselective reactions of iron enolate species derived from [(η 5 -C 5 H 5 )(CO)Fe(CO)(PPh 3 )CH 2 R] have been studied extensively [ 60 , 62 , 64 , 317 , 319 , 341 ]. Usually the iron chiral auxiliary [(η 5 -C 5 H 5 )Fe(CO)(PPh 3 )] exerts powerful stereochemical control over the reactions of the attached acyl ligand [ 61 , 63 ]. By treating the acetyl complex with butyllithium we can efficiently generate the corresponding enolate, which may be trapped by a variety of allyl halides, and further treatment with butyllithium generates the corresponding E -enolates completely stereoselectively.…”