Enantioselective reduction of benzoyl derivatives of ferrocene and ruthenocene; Optically active carbinols and carbenium ions

Synthesis, structures and reactions of some metallocene alcohols

“…Crystals grown from a solution containing a mixture of the diastereomers of 1,1 0 -diphenyl-1,1 0 -(1,1 0 -ruthenocenediyl)dimethanol [19,45], 12, were found to contain solely the meso (SR) diastereomer (Fig. 7).…”

“…Crystals suitable for single-crystal X-ray diffraction were grown by slow cooling of a saturated pentane solution to )30°C. 1 [43,44], and 12 (omitting the chiral auxiliary used in the literature) [45].…”

Efficient regio- and diastereo-controlled synthesis of 1,1′- and 1,1′,2,2′-functionalised ferrocenes and the formation of 2-oxa[3]ferrocenophanes

“…The loss of optical activity of 1,1Ј-bis(hydroxymethyl)ferrocenes and 1,1Ј-bis(hydroxymethyl)ruthenocenes, which had been prepared by asymmetric reduction, has been demon- strated in an acidic medium by extensive 1 H NMR studies. 36 The 2-oxa [3]metallocenophane has been proposed as a vehicle to achieve this epimerisation. These observations concerning the lack of optical stability at the α-position of a 1,1Ј-substituted ferrocene system are in stark contrast to that reported for monosubstituted ferrocenes.…”

Stereospecific Synthesis, Structural Characterisation and Resolution of 2‐Phospha[3]ferrocenophane Derivatives – a New Chiral Scaffold

“…Scheme 2. Diol 2a can be obtained easily, albeit in an expensive and redundant way, by CBS reduction [17] of the corresponding diketone, 1,1Ј-dibenzoylferrocene. Alternatively, [18][19][20] diol 2a can be obtained from the 1:1 mixture of the meso and dl diols produced by NaBH 4 reduction of 1,1Ј-dibenzoylferrocene, by repeated crystallisations from ethyl acetate/hexane. The meso diol 2aЈ was obtained by fractional crystallisation of the meso/dl (2:1) diastereomeric mixture, which is produced when the same diketone is reduced with LiAlH 4 in ether.…”