Transformations of chiral iron complexes used in organic synthesis. Reactions of .eta.5-CpFe(PPh3)(CO)COCH3 and related species leading to a mild, stereospecific synthesis of .beta.-lactams

Stereoselective conjugate addition reactions of lithium amides to α,β-unsaturated chiral iron acyl complexes [(η5-C5H5)Fe(CO)(PPh3)(COCHCHR)]

“…respectively. In each case, fractional crystallisation gave (S,3R)-19 and (S,3S)-20 in >97% d.e., with the configuration of the b-centres within (S,3R)-19 and (S,3S)-20 assigned relative to the iron centre by analogy with the known sense of asymmetric induction upon conjugate addition of lithium dibenzylamide to the (E)-crotonoyl complex [17], and by the characteristic 1 H NMR chemical shifts of the aprotons [24]. The observed stereocontrol in these reactions is consistent with a mechanism involving lithium co-ordination to the acyl oxygen and subsequent delivery of the dimethylamide to the unhindered face of the cinnamoyl ligand in the s-cis conformation (Scheme 2).…”

“…166-168°C; C 14 H 22 ClNO 2 requires C,61.9;H,8.1;N,5.2%;Found C,61.7;H,8.3;N,5 3.9. Preparation of (RS,RS,RS,RS)-(g 5 -C 5 (24) n-BuLi (1.50 ml, 2.40 mmol) was added to a solution of bis- (3,4-dimethoxybenzyl)amine (0.860 g, 2.70 mmol) in THF (10 ml) at 0°C and stirred for 1 h before cooling to À78°C. A solution of 12 (0.480 g, 1.00 mmol) in THF (5 ml) was added via cannula, and after 14 h a solution of acetaldehyde (0.500 ml, 9.0 mmol) in THF (5 ml) was added via cannula and stirred for 3 h at À78°C before warming to rt.…”

2.06 Formation of Enolates

“…224,225 If R 1 ¼ H, the terms syn and anti make no sense anymore, but two diastereomers are distinguishable. [226][227][228] Bu i 2 A1, CISn and BrSn enolates produce one diastereomer with good selectivity. A C-bonded enolate of an iron-acyl complex can be generated with [AuCl(PPh 3 )] (equation 41).…”

A New and Expedient Diastereoselective Synthesis of α‐(Hydroxyamino)phosphonates and α‐Aminophosphonates by Silyl Triflate Promoted Diethyl Phosphite Addition to Chiral N‐Benzyl Nitrones

“…This concept called for a reductive operation to transform the hydroxyamino group into the corresponding amine. Various methods for the reduction of N,N-dialkylhydroxylamines have been reported, including catalytic hydrogenation, [19] reduction with SmI 2 , [19] Zn/HCl, [19] Raney Ni, [19,20] aqueous TiCl 3 , [21,22] and Zn/ Cu(OAc) 2 . [8d,23] In our hands, the method of choice was strictly dependent on the nature of the hydroxylamine to be reduced.…”