Organische Synthesen mit Uebergangsmetallkomplexen XXXVIII +. Umwandlung von Tri(methylen)methan- in 1,3-Dienliganden an Chrom- und Eisenkomplexen

Article abstract of DOI:10.1016/0022-328X(89)80006-3

1,3-Diene complexes and 1,3-dienes have been obtained from tri(methylene)-methane complexes L_n-1M (III) of chromium and iron n-1M = Cr(CO)4, Fe(CO)3; Y = OH, CO2Et, CH2OH> by transformation of the α-CH2Y moiety into terminal =CH2 and =CHY groups, respectively.The transformation of CH2Y into a =CH2 group can be achieved by a suprafacial nucleophilic 1,4-substitution of Y.A transformation of CH2Y into =CHY takes place by metal-induced 1,4-hydrogen transfer.The iron complex IIIa undergoes (acid-catalyzed) nucleophilic 1,4- and 1,1-substitution reactions, respectively.Thus, from diastereomers IIIaA and B the 2-benzyl-1,3-diene complex VIII is obtained by 1,4-substitution, whereas diastereomer IIIaC gives a tri(methylene)methane complex (IX) by a 1,1-substitution without undergoing a change in its configuration.The corresponding chromium complex IIIdA under protic conditions yields the (metalfree) dienes XI and XII.By contrast, the chromium complexes IIId-f at 50 deg C in inert solvents yield 3-benzyl-1,3-dienes (Va-c) and 3-methyl-1,3-dienes (V' a-c) by metal-induced 1,4-hydrogen shifts.The corresponding enols Va and V' a (Y = OH) rearrange immediately to give the aldehydes VI, VI' and VII.