Stereoselektive Synthesen von substituierten Tricarbonyl[tris(methylen)methan]eisen(0)‐Komplexen

Stereoselective Syntheses of Substituted Tricarbonyl[tris(methylen)methan]iron(0) Complexes The complexes 3 , 9 , 10 , 22 , and 23 with one, two, and three Me substituents at the tris(methylen)methane moiety have been synthesized from the (acyloxy‐1,3‐diene)(tricarbonyl)iron(0) complexes 1 , 4 , 5 , 20 , and 21 , respectively, by ionic hydrogenation with BF 3 and Et 3 SiH at −78° in CH 2 C1 2 . These reductions are completely stereoselective, and their course can be predicted by assuming a dominant stereoelectronic control of the reaction. Formation of the carbocationic intermediates 11 from 4 and 12 from 5 , e.g. , takes place only if the dissociating OC bond is antiperiplanar to the donor C(β)Fe bond. Fast H‐transfer then converts the intermediate 11 to 9 and 12 to 10 . The configurations of 17 and 20 can be deduced from the structure of 22 and those of 18 and 21 from that of 23 . An X‐ray structure determination of (1 R ,4 S )camphanoate (−)‐ 13 derived from alcohol (−)‐ 7 confirms the configuration of 5 deduced above, The structures of the complexes 9 and 10 , 22 and 23 were determined by their unique NMR spectra. The diastereoisomeric complexes 6 and 7 have been synthesized from aldehyde 8 with MeMgI, the diastereoisomers 17 and 18 analogously from 16 or from methyl ketone 19 by reduction with LiAlH 4 . Optically active starting materials (+)‐ 1 , (−)‐ 13 , (+)‐ 20 , and (+)‐ 21 gave, by ionic hydrogenation, the complexes (−)‐(3 R )‐ 3 , (+)‐(2 S ,4 S )‐ 10 , (−)‐( R , R , S )‐ 22 , and (−)‐( R , R , R )‐ 23 respectively, with known absolute configurations.