Synthesis of chiral (7 R)-[η 6-5-( N, N-dimethylamino)-7-formyl-1,3-benzodioxole]chromium complex and its application in the synthesis of optically active cis-β-lactams

• Published in: Journal of organometallic chemistry Vol. 632; no. 1; pp. 27 - 40
• Main Authors: Filomena Costa, M, da Costa, M.Rute G, Marcelo Curto, M.J, Magrinho, M, Damas, Ana M, Gales, Luis
• Format: Journal Article
• Language: English
• Published: LAUSANNE Elsevier B.V 24.08.2001; Elsevier
• Subjects: Asymmetric synthesis; Chemistry; Chemistry, Inorganic & Nuclear; Chemistry, Organic; Chromium; Cycloadditions; Imine complexes; Physical Sciences; Science & Technology; β-Lactams; Chromium; Asymmetric synthesis; Cycloadditions; Imine complexes; β-Lactams; chromium; ASYMMETRIC-SYNTHESIS; ENANTIOSELECTIVE SYNTHESIS; STAUDINGER REACTION; RACEMIC MIXTURES; IMINES; RESOLUTION; cycloadditions; ALCOHOLS; beta-lactams; asymmetric synthesis; imine complexes; DIASTEREOSELECTIVE SYNTHESIS; 2+2 CYCLOADDITION; STEREOSELECTIVE-SYNTHESIS
• ISSN: 0022-328X; 1872-8561
• DOI: 10.1016/S0022-328X(01)00806-3

Prochiral imine chromium complexes derived from the racemic (5- N, N-dimetylamino-7-formyl-1,3-benzodioxole)chromium complex 4 and several amines reacted with acetoxylketene, generated from its corresponding acid chloride and triethylamine, to produce the corresponding β-lactam complexes 6a, 6b and 6c with complete control of cis-diastereoselectivity. In a similar manner, the imine condensation of the chiral imine complexes 11a and 11b, derived from the chiral aldehyde complex 4I, not only provides complete cis-diastereoselection of the β-lactam complexes 12a and 12b, but remarkable enantioselectivities as well. X-ray crystal structures of 4I and 12a were obtained and the mechanics implications within the context of the general mode proposed by several authors for the stereochemical outcome of the Staudinger reaction are in agreement with these results. Condensation of acetoxyacetyl chloride with racemic imine complexes derived from [η 6-5-( N, N-dimethylamino)-7-formyl-1,3-benzodioxole]tricarbonylchromium ( 4) produced β-lactams with complete cis-diastereoselection. In this context, the resolution of 4 allowed the use of its ( R) form 4I in the asymmetric Staudinger reaction. The corresponding β-lactam complexes 12 were obtained with high levels of enantiomeric excess. X-ray crystal structural determinations of 4I and 12a are reported.