Search

This paper presents a study of the rhodium-catalyzed silylformylation [Rh(I) precatalyst, PhMe2SiH, THF, carbon monoxide (15−1500 psig), 23 °C] of aldehydes. This new catalytic homologation reaction produces α-(silyloxy) aldehydes in a highly efficient manner. Rhodium(I) appears to be the optimum transition metal for the catalytic process. The reaction is optimized at carbon monoxide pressures over 50 psig. It appears that PhMe2SiH is the silane reagent of choice. The silylformylation of carbonyl compounds is very general for aldehyde substrates (aromatic, heterocyclic, alkyl, and ferrocenyl: 16 examples presented) and can tolerate the presence of internal alkene and alkyne, ester, and acyclic ketone functional groups. Aldehydes with α-substituents show moderately good diastereoselectivity, producing the syn-α-(silyloxy) aldehyde (10 to 20:1, syn:anti) as the major product. Ketone substrates possessing β-hydrogens yield only silyl enol ether without concomitant hydrosilylation coproducts. Imine substrate...

Ferrocenecarboxaldehyde was successfully condensed with fluorene derivatives to afford a series of new complexes, (eta5-C5H5) Fe(eta5-C5H4CH=(9- fluorenyl)) where fluorenyl = 1A, 2-bromo: 2a, 2,7-dibromo; 3, 2-nitro. The ferrocene-fluorenyl derivatives la and 2a were converted to the monocarboxaldehyde, tributylstannyl, bis(carboxaldehyde), and bis(tributylstannyl) complexes (lb, lc, 2b, and 2c, respectively). Complexes lb and 2b were characterized by single-crystal x-ray molecular structures. The fluorenyl ring systems were tilted out of the eta5-C5H4 plane by 39 deg. Treatment of lc and 2c with I2 afforded the mono- and bis(iodo)fluorenyl complexes ld and 2d, respectively. The reactivity of complexes 2a-d was explored. The alkynylation (alkyne, L2PdCl2, CuI, PPh3) of 2a was an extremely poor reaction giving little or no cross-coupling. Complex 2b did not undergo the Knoevenagel polycondensation with bis(cyanoacetate) comonomers. Treatment of 2c with acid chlorides under Stille cross-coupling conditions afforded ketone product and iodobenzene showed no cross-coupling. Complex 2d did copolymerize very cleanly with 2,5(diethynyl)-1,4-(decoxy)benzene using palladium catalysis to afford a soluble, high-molecular weight conjugated polymer, 4. A model compound, 5, was prepared from cross-coupling ld with 2,5-(diethynyl)-1,4- (decoxy)benzene.

Selective transmetalation of one tri-n-butylstannyl group of [η 5 -(Bu 3 Sn) C 5 H 4 ] Fe (1) with 1 molar equiv of n-BuLi, followed by treatment with Ph 2 PCl or N,N-dimethylformamide, produced 1-(tri-n-butylstannyl)-1'-(diphenylphosphino) ferrocene (3) and 1'-(tri-n-butylstannyl)-1-ferrocenecarboxaldehyde (8), respectively. Compound 8 was converted to 1'-(tri-n-butylstannyl)-1-[(dimethylamino) methyl] ferrocene (9) by reductive amination with dimethylamine and sodium cyanoborohydride. Subsequent treatment of 3 or 9 with 1 molar equiv of n-BuLi resulted in selective transmetalation of the tri-n-butylstannyl group. The selective transmetalation was utilized to prepare new ferrocenylphosphine ligands

The synthesis and characterization of (R{sup 1}R{sup 2}Si(2-pyridyl))PdCl{sub 2} (R{sup 1} = Me, R{sup 2} = phenyl; 3) are presented. Complex 3 crystallizes in the monoclinic space groups P2{sub 1}/n (Z=4) with {beta} = 99.98 (1){degree} and a = 12.208 (2) {angstrom}, b = 12.651 (3) {angstrom}, c = 14.079 (2) {angstrom}. The single-crystal study showed the six-membered chelate ring to be in a boat conformation with the palladium and silicon atoms as the apexes out of plane. Cross-coupling reactions of organostannanes catalyzed by (Me{sub 2}Si(2-pyridyl))PdCl{sub 2} (2) were examined. Vinyltributylstannane undergoes cross coupling in high yield when treated with benzoyl chloride and 1 mol % of 2 in di- chloromethane, whereas treatment with iodobenzene results in formation of Me{sub 2}Si(2-pyridyl)PdI{sub 2} (4) with only a minor amount of cross coupling observed. The addition of LiCl did not affect the cross-coupling reaction when (PPh{sub 3}){sub 2}PdCl{sub 2} was used as the precatalyst. When trimethyl(phenylethynyl)stannane was used, the addition of lithium chloride did not decrease homocoupling of the organostannane reagent for precatalyst 2, whereas for (Ph{sub 3}P){sub 2}PdCl{sub 2} homocoupling of the stannane partner was not observed with or without added lithium chloride.

Le complexe du titre, C 17 H 20 FeO 2 , cristallise dans P2 1 /n avec Z=8; affinement jusqu'a R=0,063. Discussion des donnees RMN et de la reaction du titre