Christopher J. Richards

Synthesis of phosphinoferrocenyloxazolines. New ligands for asymmetric catalysis

Abstract Condensation of β-hydroxy alcohols with ferrocenyl chloride gave the corresponding amides which were dehydrated to give ferrocenyl oxazolines in good overall yield. Subsequent lithiation with n -BuLi in the presence of TMEDA and addition of PPh 2 Cl led to the isolation of ( S )-( S )- i Pr-phosferrox and ( S )-( S )-Me-phosferrox ligands 1 and 2 . Their corresponding diastereoisomers, ( S )-( R )- i Pr-phosferrox and ( S )-( R )-Me-phosferrox 3 and 4 were obtained via the intermediacy of removable trimethylsilyl blocking groups. The CD spectra of 1 – 4 and their parent ferrocenyl oxazolines 9 and 10 were obtained.

SYNTHESIS AND APPLICATION OF CATIONIC 2,6-BIS(2-OXAZOLINYL)PHENYLPALLADIUM(II) COMPLEXES

Abstract Treatment of 1,3-bis(2-oxazolinyl)benzenes with LDA/TMEDA followed by the addition of PdBr2(1,5-COD) gave 2,6-bis(2-oxazolinyl)phenylbromopalladium(II) complexes. Subsequent bromide abstraction with silver salts provided a series cationic 2,6-bis(2-oxazolinyl)-phenylpalladium(II) complexes that effectively catalyse the addition of α-cyano carboxylates to methyl vinyl ketone.

A metallocene molecular gear

Abstract In a five step synthesis (ethynylcyclopentadienyl)(tetraphenylcyclobutadiene)cobalt is produced in 19% overall yield from sodium carbomethoxycyclopentadienylide. Subsequent cross-coupling with 9-iodoanthracene (76%) and addition of benzyne (52%) gave (9-triptycylethynylcyclopentadienyl)(tetraphenylcyclobutadiene)cobalt, the first example of a metallocene containing molecular gear.

Synthesis of a C3-symmetric ferrocenylphosphine and its application to the Suzuki reaction of aryl chlorides

(pS,pS,pS)-Tris(2-methylferrocenyl)phosphine 1 was synthesised in 62% yield from (S)-2-ferrocenyl-4-(1-methylethyl)oxazoline. In combination with Pd2dba3 this novel C3-symmetric ligand generates a catalyst for the Suzuki reaction of aryl chloride substrates, these reactions proceed readily at 60°C in dioxane.

Simple phosphinite–oxazoline ligands for asymmetric catalysis

Abstract 4-(Hydroxymethyl)oxazolines, derived from (S)-serine methyl ester and a variety of acid chlorides (RCOCl), were reacted with Ph2PCl to give new phosphinite–oxazoline P–N ligands. These mediate the palladium catalysed asymmetric alkylation with dimethyl malonate with the following racemic propenyl substrates R1CHCHCH(OX)R1: (a) R1=Ph, X=Ac—96% e.e.(S) with R=Ph; (b) R1=Me, X=CO2tBu—70% e.e.(S) with R=(η5-C5H4)(η4-C4Ph4)Co.

A rapid approach to ferrocenophanes via ring-closing metathesis

Abstract The synthesis of [4]ferrocenophanes containing a ( Z )-1,4-but-2-endiyl bridge is described. Starting from either achiral (R=H), meso (R=Me, Ph) or scalemic (R=Me, 4-MeOC 6 H 4 ) 1,1′-di{CHR(OAc)}ferrocenes, vinylation with a mixture of vinyl magnesium chloride and zinc chloride proceeds readily and with significant retention of configuration to give allylferrocenes in an isomer ratio of >3:1. Ring-closing metathesis with Ru(CHPh)Cl 2 (PCy 3 ) 2 results in conversion of the achiral (R=H) and all the meso -diastereoisomers (R=Me, Ph, 4-MeOC 6 H 4 ) to their corresponding cis -disubstituted [4]ferrocenophanes. Only a single trans -disubstituted [4]ferrocenophane was synthesised (R=Me), the larger substituents preventing cyclisiation by this method.

Towards novel biolabels: synthesis of a tagged highly fluorescent Schiff-base aluminium complex

Abstract Starting from 3-(4-hydroxyphenyl)propanoic acid, formylation ortho to the phenol and condensation with ortho -aminophenol gave a novel functionalised Schiff-base ligand. Formation of the N -hydroxysuccinimidyl ester and non-aqueous complexation with AlEt 2 Cl gave a novel fluorescent biolabel displaying a Stokes shift of 100 nm. The efficacy of the new system was demonstrated by its attachment to rabbit IgG.

ASSIGNMENT OF 1H NMR CHEMICAL SHIFTS IN 1,2- AND 1,1'-DISUBSTITUTED FERROCENES

Abstract The effect of 29 commonly encountered substituents on the chemical shifts of α, β and C 5 H 5 positions in monosubstituted ferrocenes are tabulated and employed for determining 1 H NMR assignments in 1,2- and 1,1′-disubstituted ferrocene derivatives.

2-Nitroferrocenyloxazolines: precursors to nitrofulvalenes and derivatives of (pS)- and (pR)-2-aminoferrocenecarboxylic acids

Abstract Diastereoselective lithiation of (S)-2-ferrocenyl-4-(1-methylethyl)oxazoline, followed by addition of N2O4, gave (S)-2-[(pS)-2-nitroferrocenyl]-4-(1-methylethyl)oxazoline which was subsequently converted into derivatives of (pS)-2-aminoferrocenecarboxylic acid. The corresponding (pR)-derivatives were obtained through use of a removable TMS blocking group. The 2-nitroferrocenyloxazolines produced in this work underwent facile photo-decomplexation to give 2-nitrocyclopentadienyliden-1,3-oxazolidenes.

The first example of an enantiopure planar chiral hydroxyferrocene ligand

Abstract Lithiation of 2-ferrocenyl-4,4-dimethyloxazoline followed by addition of bis(trimethylsilyl)peroxide led to the isolation of air-stable 2-(2-hydroxyferrocenyl)-4,4-dimethyloxazoline. Repetition of this procedure on ( S )-2-ferrocenyl-4-(1-methylethyl)oxazoline gave the lithium salt of ( S )-2-(( p S )-2-hydroxyferrocenyl)-4-(1-methylethyl)oxazoline, a stable precursor to the first example of an enantiopure hydroxyferrocene ligand.