Chemistry of the podocarpaceae LXXI. Preparation, structure, and reactions of some (arene)tricarbonylchromium(0) complexes. Crystal structure of α-tricarbonylchromium(0)

Article abstract of DOI:10.1016/0022-328X(88)83005-5

Tricarbonyl<(8,9,11,12,13,14-η)methyl podocarpa-8,11,13-trien-19-oate>chromium(0) (7), tricarbonyl<(4a,5,6,7,8,8a-η)-1,2,3,4-tetrahydronaphthalene>chromium(0) (11) and (benzene)tricarbonylchromium(0) (10) were prepared and examined.Complex 7 was obtained as a mixture of diastereomers, an X-ray structural determination showing that the α-isomer possesses a near eclipsed conformation, in agreement with the conformation in solution deduced from 400 MHz 1H NMR analysis.Carbanions derived from 1,3-dithiane, 2-methyl-1,3-dithiane and 2-(2,2-dimethoxyethyl)-1,3-dithiane (24), and the dianion derived from 2,2'-methylenebis-1,3-dithiane (27) were prepared and brought into reaction with the complexes.Compounds 23 and 33 resulted from regioselective attack on 7 at the site predicted.Treatment with methyl electrophiles of the dithianyl η⁵-intermediate leading to 22 did not give products of acetyl incorporation.Arene lithiation-electrophilic quenching of 7 gave a mixture of compound 6 and its C(14) regioisomer along with the novel ketone 39 and its C(14) regioisomer.