Binuclear clusters in organic synthesis. Synthetic and mechanistic studies of the reduction of .alpha.,.beta.-unsaturated carbonyl compounds by sodium hydrogen octacarbonyldiferrate

Abstract

Physiol., 4b, 989 I -1100 115 0 500 (nm) Figure 3. Electronic spectrum of a lecithin membrane: A, Hem. Mn(II1) membrane; B, treatment of A with NaOCl for 1 min; C, treatment of B with aqueous ascorbic acid for 1 min. concentration) containing KCl(1 .O M ) to adjust its ionic strength. After 1 min, most of the Mn(II1) in the membrane was effectively converted into Mn(1V) (more than 80%) as ascertained by electronic spectral changes as shown in Figure 3. Spectra were obtained after washing the membranes rapidly three times with aqueous alkaline solution ( p H 12) to remove traces of NaOCl absorbed on the surface.The Hm.Mn(IV) in the membrane was stable enough for spectroscopic measurements. The Mn(IV) membranes were then treated with aqueous ascorbic acid (0.01 M ) , containing KCl (1.0 M ) , for 1 min. After rapid washing with the aqueous solution of p H 12, Hm-Mn(1V) was estimated by electronic spectral changes, which showed that most of the Hm-Mn(1V) was converted to Hm.Mn(II1) (70-80%) (Figure 3).Spontaneous transport of ascorbic acid through the lecithin-Hm.Mn(II1)-n-decane membrane from B (0.01 M ascorbic acid and 1.0 M KC1) to A (1.0 M KC1) was measured by the spectroscopic determination of ascorbic acid (265 nm) in A. It was (3.8 f 0.3) X 10-I2 mol min-I, ca. 3000 times slower than the reduction of the Mn(1V) membrane by ascorbic acid. The continuous electron transfer through the lecithin-Hm-Mn membrane from the ascorbic acid solution (5.0 X M ) to the sodium hypochlorite solution (1.3 X 10-l M ) was also studied by use of a salt bridge. The amount of the ascorbic acid oxidized was 7.4 X mol rnin-l (ca. 2.3 turnover per M n in 25 min), 195 times faster than the rate of spontaneous transport. This strongly indicates that the oxidation-reduction did not result from material transport but from one-way electron transport as shown in Figure 1. Treatment of Mn(1V) membranes with an aqueous solution of p H 4 containing 1.0 M KCI instead of aqueous ascorbic acid again reduced Mn(1V) to Mn(II1) as in the homogeneous system,' but the rate was considerably slower than that of the ascorbic acid reduction.These electron translocating membranes are versatile, allowing the preparation of one-way oxidation-reduction electron transport systems or the effective separation of electrons from positive holes.

Synthesis of triiron carbonyl cluster complexes containing isomeric triply bridging acimidoyl or alkylidenimido group derived from the reduction of organic nitriles

“…The greater stability of the C-D and Fe-H bond pair over the C-H and Fe-D bond pair is qualitatively consistent with a calculation by Coliman et al for a related case. 26 Significantly, no hydrogen-deuterium scrambling was observed in the monodeuterio-Sa, DFe3(CH3C=NH)(CO)9, even at 65 °C.…”

Reductions of conjugated carbonyl compounds with copper hydride - preparative and mechanistic aspects

“…Table II presents the results obtained with two acyclic ketones, 2,2,6,6-tetramethylhept-4-en-3-one (7) and chalcone (8). Conjugate reduction is again the preferred course of reaction; the Na complex is clearly superior, giving no trace of 1,2 reduction under a variety of conditions.…”

“…Additional Eu(fod)2 provided separation of the signals due to the C-l and C-2 protons in the methyl 3-phenylpropionate product (31). With 43 mg of Eu(fod)2 added to the solution, a multiplet (t of t, 1 H, = 7, Ji.o - 3 Hz) assigned to H-l appeared upfield of a second multiplet (br d, ~2 H, J= 7 Hz).…”

“…Experimental Section [3,a(j,4'a,7,a,7'a/3]-3'a,4',7,,7'a-Tetrahydrospiro[cyclopentane-l,-8'- [4,7]methanoisobenzofuran]-l',3'-dione (1) was synthesized as previously described.7 Colorless crystals with well-defined faces were obtained by recrystallization from solution in benzene by vapor diffusion of 60-110 °C petroleum ether into the benzene solution. Preliminary Weissenberg and precession photographs of a small crystal (ca.…”

Efficient Conjugate Reduction of α,β-Unsaturated Carbonyl Compounds by Complexation with Aluminum Tris(2,6-diphenylphenoxide)

“…The conjugate reduction of α,β-unsaturated carbonyl compounds remains an active area of organic synthesis − (1,2 vs 1,4) of these compounds, several methods have been thoroughly investigated, and each method has characteristic advantages. Unfortunately, however, these existing methods also have some disadvantages: strict reaction conditions and the structure of the reaction substrate affect the chemoselectivitiy and yield of the products.…”