Diastereoselective formation of tricarbonyliron(0) complexes of 1-aza-1,3-dienes bearing chiral substituents

Steroids as chiral model compounds for selective reactions with metals

“…In some cases, the diastereomers could be separated by crystallization [12][13][14][15]. In solution, epimerization of pure diastereomers has been observed.…”

The chemistry of (1-azabuta-1,3-diene)tricarbonyliron(0) complexes

“…For example, reaction of diironnonacarbonyl with 1-azabuta-1,3-dienes (14) and (16) derived from cinnamaldehyde and a-substituted benzylamines produces the diastereomeric complexes 15 and 17, respectively (Scheme 4) [4,9]. When the asubstituent R of the azabuta-1,3-diene is a methyl group, a 1:1 mixture of diastereoisomers is formed.…”

“…12), a mixture of E,E (C‚N) (12a) and E,Z (C‚N) (12b) geometrical isomers is usually formed. Complexation of the 1-azabuta-1,3-diene mixture (12) to the tricarbonyliron(0) moiety by reaction with Fe 2 (CO) 9 leads to complex 13 in which the E,E (C‚N) ligand is selectively coordinated to the tricarbonyliron(0) moiety (Scheme 3) [4]. Evidence for the stereochemistry of the ligand was obtained from NOE difference spectroscopy.…”

“…Initial reaction of Fe 2 (CO) 9 with a 1-azabuta-1,3-diene has been shown to lead to the formation of intermediate complexes 30 [15]. In these complexes, the 1-azabuta-1,3-diene is co-ordinated to the tetracarbonyliron(0) moiety via the nitrogen lone pair (r-N complex).…”

“…In cases where isolation of the starting 1-azabuta-1,3-diene is problematic [e.g. [6][7][8], reaction of the crude ligand mixture with a source of the tricarbonyliron(0) moiety [usually Fe 2 (CO) 9 ] leads to complexes 9-11 in good yields (Scheme 2) [5,8]. In these examples, the formation of the intermediate 1-azabuta-1,3-dienes (6)- (8) was observed by 1 In the synthesis of 1-azabuta-1,3-dienes bearing a substituent other than H at C-2 (e.g.…”