Regioselective Chlorocarbonylation of Polybenzyl Cores and Functionalization Using Dendritic and Organometallic Nucleophiles

Regiospecific chlorocarbonylation of the polybenzyl cores PhCH2CH2Ph, C6(CH2CH2Ph)6, 7, and {CH(CH2Ph)2}4-1,2,4,5-C6H2, 8, in the para position of the benzyl groups gives the chlorocarbonyl derivatives 2, 9, and 10, respectively, in good yields. The octachlorocarbonyl derivative 10 reacts with Newkome's aminotripod NH2C(CH2OCH2CH2CN)3 to give the 24-nitrile dendrimer 13 which is characterized by its molecular peak in the MALDI TOF mass spectrum and with (5-aminopentyl)-1-ferrocene to give the octaferrocene complex 14. Reactions of 2, 9, and 10 with sodium methanolate in methanol gives the methyl esters 3, 15, and 16 which are reduced by LiAlH4 to the primary alcohols 4, 17, and 18; reactions of these alcohols with NaI and BF3·Et2O yield the iodomethyl derivatives 5, 19, and 20. The organoiron nucleophile [FeIICp(η5-C6Me5CH2)], 1, reacts with 5, 19, and 20 leading to C−C bond formation and recovery of the aromatic structure of the ligand. This reaction with 5 yields a soluble complex, [FeIICp(η6-C6Me5CH2CH2C6H4CH2-)]2, 6, in which the two redox groups, separated by 14 carbon atoms, are independent, being reversibly reduced at approximately the same potential in an overall two-electron wave recorded by cyclic voltammetry. The analogous reaction with 19 and 20, however, gave almost insoluble hexa- and octa-iron complexes 21 and 22 with mediocre purities.