Reduction proce

Mercuric chloride test. Add mercuric chloride solution to formic acid or a solution of formate and w arm. A white precipitate of mercurous chloride, insoluble in dil. HCl, is produced. Sometimes the reduction proceeds as far as metallic mercury, which appears as a grey precipitate. 

From these facts, a mechanism of the Rosenmund reduction has been proposed, in which the formation of the acylpalladium species 893 is the first step of the aldehyde formation and also the decarbonylation, although the Rosenmund reduction proceeds under heterogeneous conditions[744]. 

A -Pyrazolines are obtained by the reduction of pyrazoles with sodium and alcohol, by catalytic hydrogenation on palladium or by electrochemical means (B-76MI40402). In some cases the reduction proceeds further yielding pyrazolidines and open-chain compounds. 

When saturated steroidal ketones are reduced in ammonia, an alcohol is usually present to act as a proton donor and high yields of steroidal alcohols are obtained. Under these conditions, reduction probably proceeds by protonation of the radical-anion (or ketyl) (61), which results from a one electron addition to the carbonyl group, followed by addition of a second electron and proton. Barton has proposed that reduction proceeds via protonation of the dianion (62) arising from addition of two electrons to the carbonyl group. This proposal implies that the ketyl (61) undergoes addition of a second electron in preference to undergoing protonation by the... 

Huffman found that treatment of cholan-12-one (65b) with lithium and ammonia for 2 hours followed by addition of propanol gives 40 % of a pinacol together with 48.5 % of 12-ols in which the ratio of 12j5 12a is 19 1. This predominance of the 12 -ol was interpreted in terms of slow formation of a dianion of type (62) followed by its equilibration to the thermodynamically most stable configuration, i.e. one which affords the 12j5-ol upon protonation. An alternative explanation is that reduction in the presence of methanol involves protonation of a ketyl such as (61) by methanol, whereas in the absence of methanol reduction proceeds via the dianion (62) which is protonated on... 

Some data have been obtained on the activity of the catalyst in a reduced state [for nickel (141,143,144), palladium (144°), and molybdenum (145, 145a). In the case of nickel catalysts the formation of nickel in the zero oxidation state takes place during the reduction of the surface organometallic compound by H2. The infrared spectrum shows the total restoration of the concentration of Si—OH groups (139), so the reduction proceeds according to the scheme ... 

Reduction of aromatic rings with lithium or calcium " in amines (instead of ammonia—called Benkeser reduction) proceeds further and cyclohexenes are obtained. It is thus possible to reduce a benzene ring, by proper choice of reagent, so that one, two, or all three double bonds are reduced. Lithium triethylborohy-dride (LiBEtsH) has also been used, to reduce pyridine derivatives to piperidine derivatives." ... 

Amides can also be deacylated by partial reduction. If the reduction proceeds only to the carbinolamine stage, hydrolysis can liberate the deprotected amine. Trichloroac-etamides are readily cleaved by sodium borohydride in alcohols by this mechanism.237 Benzamides, and probably other simple amides, can be removed by careful partial reduction with diisobutylaluminum hydride (see Section 5.3.1.1).238... 

Many enantioselective catalysts have been developed for reduction of functional groups, particularly ketones. BINAP complexes of Ru(II)C12 or Ru(II)Br2 give good enantioselectivity in reduction of (3-ketoesters.49 This catalyst system has been shown to be subject to acid catalysis.50 Thus in the presence of 0.1 mol % HC1, reduction proceeds smoothly at 40 psi of H2 at 40° C. 

The mechanism by which the Group III hydrides effect reduction involves activation of the carbonyl group by coordination with a metal cation and nucleophilic transfer of hydride to the carbonyl group. Hydroxylic solvents also participate in the reaction,59 and as reduction proceeds and hydride is transferred, the Lewis acid character of boron and aluminum becomes a factor. 

It is well known that in the cyclization of a y-hydroxy aldehyde to form the corresponding six-membered ring hemiacetal through intramolecular cyclization the hemiacetal form always predominates (48). This might account for the fact that no noticeable carbonyl absorption has been observed in the IR and NMR spectra of 54. However, the equilibrium between the hemiacetal and the aldehyde forms might shift in favor of the aldehyde form as the borane reduction proceeds until 54 is completely transformed to 55. 

The keto-derivative 21 is of interest because the relatively unreactive 3,5-cyclo-heptadienone substrate, which towards most dienophiles reacts with double bond isomerization, affords the desired endoperoxide (Eq. 16)33). Diimide reduction proceeds smoothly, leading to the keto-peroxide 21 in over 90% yield. 

Klemm, Olson, and White discovered that the double bond in 117 may be reduced electrochemically with overall stereospecific trans addition of hydrogen to the double bond 120>. It was suggested that reduction proceeds by an initial two-electron reduction of the protonated starting material to carban-... 

Binuclear Al111 complexes for MPV reduction have been developed. In the presence of 5mol.% of the bidentate catalyst (Scheme 69, compound (R)), the reduction proceeds smoothly at room... 

The reduction of R3SnCH2I on Hg has been studied in detail, where R = CH3, C2H5 or Ph86. The reduction proceeds through the formation of the corresponding radical anion ... 

The potential of an electrode measured relative to a standard, usually the SHE. It is a measure of the driving force of the electrode reaction and is temperature and activity dependent (p. 230). By convention, the half-cell reaction must be written as a reduction and the potential designated positive if the reduction proceeds spontaneously with respect to the SHE, otherwise it is negative. If the sign of the potential is reversed, it must be referred to as an oxidation potential. 

Polarographic studies of hydralazine and related compounds were reported by Giovanoli-Jakubezak et al (72) and by Modras (73) The reduction proceeds in two 2-electron stages with the formation of the tetrahydro derivative. Hydralazine could be determined in the... 

A cobalt complex containing this type of ligand is effective in the sodium borohydride-mediated enantioselective reduction of a variety of a,/ -unsaturated carboxylates. As can be seen from Scheme 6-8, in the presence of a catalytic amount of a complex formed in situ from C0CI2 and chiral ligand 11, reduction proceeds smoothly, giving product with up to 96% ee. The chiral ligand can easily be recovered by treating the reaction mixture with acetic acid. 

Figure 2.3 Left, reduction models. In the shrinking core or contracting sphere model the rate of reduction is initially fast and decreases progressively due to diffusion limitations. The nucleation model applies when the initial reaction of the oxide with molecular hydrogen is difficult. Once metal nuclei are available for the dissociation of hydrogen, reduction proceeds at a higher rate until the system comes into the shrinking core regime. Right the reduction rate depends on the concentration of unreduced sample (1-a) as f(a) see Expressions (2-5) and (2-6).

The tosyl hydrazones are reduced to R2CH2. Since the reduction proceeds smoothly, it constitutes a valuable method of removing carbonyl groups in organic synthesis. 

The method is applied for sensitive aromatic nitro compounds, as for example for o/p-substituted nitrobenzenes. The reduction proceeds with hydrazine/precious metal (platinum) catalysts. 

This mixture is the Huang Minion modification of the Wolff Kishner reaction. In the editor s experience it often leaps from the flask with sudden gas evolution. In addition to the expected nitrogen, at the operating temperature of around 200°C it is uncomfortably near the temperature of hydrogen evolution from glycol decomposition. The reduction proceeds much cooler in dimethyl sulfoxide or some of the alkoxyethanols as solvent. 

The selective 1,4-reduction of a,p-unsaturated carbonyl compounds is always a challenge, but it has been met successfully by the use of dithionite under phase-transfer conditions. Reduction proceeds in high yield to the total exclusion of saturated or allylic alcohols (Table 11.10) [5, 6], Exocyclic and endocyclic conjugated C=C double bonds are reduced with equal ease, whereas non-conjugated double bonds remain intact. The predominant reduction pathway for conjugated dienoic... 

A viable iron carbonyl-mediated reduction process converts acid chlorides and bromoalkanes into aldehydes [3, 6]. Yields are high, with the exception of nitro-benzoyl chloride, and the procedure is generally applicable for the synthesis of alkyl, aryl and a,(i-unsaturated aldehydes from the acid chlorides. The reduction proceeds via the initial formation of the acyl iron complex, followed by hydride transfer and extrusion of the aldehyde (cf. Chapter 8). 

Carbon dioxide has been reduced to methanol with the Everitt s salt (ES)-mediated electrode in the presence of l,2-dihydroxybenzene-3,5-disul-phonato(iron) ferrate(III) complex (Scheme 103) [408, 409]. The reduction proceeds as follows a weak coordination bond is first formed between the central metal of ES and ethanol, then the subsequent insertion of CO2 onto... 

Electrochemical carboxylation of acetophenone with CO2 coupled with nitrite reduction proceeds by the controlled-potential electrolysis of CO2-saturated acetonitrile containing [Fe4S4 (SPh)4] , N02, PhCOCH3, and a dehydration... 

The electroreduction of CO2 using a Cu cathode leads preferentially to methane and ethane [584, 585]. The selectivity is dependent on the cationic species as well as on the HCOs" concentration [586]. Hydrogen evolution prevails over CO2 reduction in a Li+ electrolyte, whereas CO2 reduction proceeds favorably in Na+, K+, and Cs+ solutions [587-589]. 

Figure 1.11 Reduction of A. vinosum hydrogenase in an FTIR cuvette by illumination in the presence of deazaflavin. An Ar-flushed solution of enzyme in the ready state, supplemented with deazaflavin and EDTA, was illuminated with white light for periods of about 4 min. After each illumination a spectrum was recorded. Reduction proceeds from the front to the back. Using the overview in Fig. 7.6, one can easily identify the several states of the enzyme by looking at the v(CO) frequency. Adapted from (Pierik et al. 1998a).

Dissolntion and reduction of crystalline Fe(III) minerals is accelerated by chelation with carboxylate ligands in the presence of Fe(ll) (Zinder et al, 1986 Blesa et al, 1987 Phillips et al, 1993 Kostka and Lnther, 1994). Therefore as soil reduction proceeds and carboxylates formed in oxidation of organic matter accumulate in solution together with Fe +, dissolntion and rednction of crystalline Fe(lll) will commence. Dissolution of oxyhydroxide coatings will therefore lag behind the initial reduction of Fe(lll). 

The origin of stereofacial selectivity in electrophilic additions to methylene-cyclohexanes (2) and 5-methylene-l,3-dioxane (3) has been elucidated experimentally (Table 2) and theoretically. Ab initio calculations suggest that two electronic factors contribute to the experimentally observed axial stereoselectivity for polarizable electrophiles (in epoxidation and diimide reduction) the spatial anisotropy of the HOMO (common to both molecules) and the anisotropy in the electrostatic potential field (in the case of methylenedioxane). The anisotropy of the HOMO arises from the important topological difference between the contributions made to the HOMO by the periplanar p C-H a-bonds and opposing p C—O or C—C cr-bonds. In contrast, catalytic reduction proceeds with equatorial face selectivity for both the cyclohexane and the dioxane systems and appears to be governed largely by steric effects. ... 

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