Absolute configuration and circular dichroism of methyl substituted tricarbonyl(1,3-butadiene)iron(0) complexes

The optically active methyl substituted tricarbonyl(1,3-butadiene)iron(0) complexes (2S,3R,4S)-(-)-1 and (2R,3S,4R)-(+)-2 have been synthesized by ionic hydrogenation with Et(3)SiH/BF3 from the acetate (-)-5 and from (+)-10 via (-)-9 in stereoselective reactions. The regioselectivity of the transformation leading from (-)-5 to 1 has been checked with deuterium labelled substrates 6, 7, and 8. An X-ray crystal structure of the (1S,4R)-camphanoate (-)-4 allowed the assignment of the absolute configurations of(-)-3, (-)-5 and hence of(-)-1. The stereoselective reduction of (2R,3R,4S)-10 via 11 to 9 and the subsequent regioselective isomerization allowed the assignment of absolute configuration to (+)-2. The chiroptical properties of (+)-1 and (+)-2 were determined and compared with those of (2S,3R)-(+)-tricarbonyl(isoprene)iron(0)[(+)-12]. Copyright (C) 1996 Elsevier Science Ltd