Catalytic reductive carbonylation

S. Cenini and F. Ragaini Catalytic Reductive Carbonylation of Organic Nitro Compounds. 1997 ISBN 0-7923 1307-7... 

The application of carbon monoxide as a reductant in organic synthesis is confined to relatively few examples. In the last 25 years, the catalytic reductive carbonylation of organic nitro compounds has become a very intense field of research. This is because a series of industrially important compounds can be obtained from nitro compounds and carbon monoxide in a single step. Very important chemicals such as isocyanates (Eq. 1), carbamates (Eq. 2) and ureas (Eq. 3) can be obtained by this methodology ... 

Transition metal alkoxycarbonyl compounds are key intermediates in a number of metal-catalyzed processes involving alkanols and carbon monoxide. The square-planar palladium(ii) complex, [Pd(phen)(G02GH3)2] 63, was determined in this context.A compound isolated as a plausible intermediate in the catalytic reductive carbonylation of nitrobenzene (viz. PhN02 + 3GO PhNGO + 2GO2) using palladium-phen-based catalysts was established by... 

This reaction proceeds in the presence o-f group VIII metal catalysts at elevated temperatures and pressures, and it has been particularly studied in the case o-f aromatic nitro compounds. Alternatively, the catalytic reductive carbonyl at i on o-f nitro compounds in the presence o-f alcohols a-f-fords the corresponding urethanes (or carbamates) ... 

Catalytic reductive carbonylation of o-nitrobenzylalcohols (55) gives 1,4-dihydro-2H-3,l-bezoxazin-2-one derivatives (56) (eq. 28) [92] ... 

CATALYTIC REDUCTIVE CARBONYLATION OF ORGANIC NITRO COMPOUNDS... 

The introduction of tritium into molecules is most commonly achieved by reductive methods, including catalytic reduction by tritium gas, PH2], of olefins, catalytic reductive replacement of halogen (Cl, Br, or I) by H2, and metal pH] hydride reduction of carbonyl compounds, eg, ketones (qv) and some esters, to tritium-labeled alcohols (5). The use of tritium-labeled building blocks, eg, pH] methyl iodide and pH]-acetic anhydride, is an alternative route to the preparation of high specific activity, tritium-labeled compounds. The use of these techniques for the synthesis of radiolabeled receptor ligands, ie, dmgs and dmg analogues, has been described ia detail ia the Hterature (6,7). 

Catalytic Reductive Coupling of Carbonyl Compounds -The Pinacol Coupling Reaction and Beyond... 

Catalytic Reductive Coupling of Alkenes and Alkynes to Carbonyl Compounds and Imines Mediated by Hydrogen... 

Hirao T (2007) Catalytic Reductive Coupling of Carbonyl Compounds - The Pinacol Coupling Reaction and Beyond. 279 53-75 Hirayama N, see Sakai K (2007) 269 233-271 Hirst AR, Smith DK (2005) Dendritic Gelators. 256 237-273 Holzwarth AR, see Balaban TS (2005) 258 1-38... 

Ihmels H, Otto D (2005) Intercalation of Organic Dye Molecules into Double-Stranded DNA - General Principles and Recent Developments. 258 161-204 Iida H, Krische MJ (2007) Catalytic Reductive Coupling of Alkenes and Alkynes to Carbonyl Compounds and Imines Mediated by Hydrogen. 279 77-104 Imai H (2007) Self-Organized Formation of Hierarchical Structures. 270 43-72 Indelli MT, see Chiorboli C (2005) 257 63-102 Inoue Y, see Borovkov VV (2006) 265 89-146 Ishii A, Nakayama J (2005) Carbodithioic Acid Esters. 251 181-225 Ishii A, Nakayama J (2005) Carboselenothioic and Carbodiselenoic Acid Derivatives and Related Compounds. 251 227-246... 

Formal isomerization of the double bond of testosterone to the 1-position and methylation at the 2-position provides yet another anabolic/androgenic agent. Mannich condensation of the fully saturated androstane derivative 93 with formaldehyde and di-methylamine gives aminoketone 94. A/B-trans steroids normally enolize preferentially toward the 2-position, explaining the regiospecificity of this reaction. Catalytic reduction at elevated temperature affords the 2a-methyl isomer 95. It is not at all unlikely that the reaction proceeds via the 2-methylene intermediate. The observed stereochemistry is no doubt attributable to the fact that the product represents the more stable equatorial isomer. The initial product would be expected to be the p-isomer but this would experience a severe 1,3-diaxial non-bonded interaction and epimerize via the enol. Bromination of the ketone proceeds largely at the tertiary carbon adjacent to the carbonyl (96). Dehydrohalogenation... 

Its structure has been confirmed by n.m.r. spectroscopy, and by its reduction with sodium and liquid ammonia to the 1,2-diol (56). It is difficult to see how catalytic reduction of (54) could lead directly to the normal carbonyl end-products, however, and on raising the temperature it is found that (54) is converted into (57) which can (and does) yield the normal carbonyl products on catalytic reduction. 

Carbonyl groups may be hydrogenated catalytically, as carbon-carbon unsaturated linkages were (p. 191). It is, however, normally more difficult to effect the catalytic reduction of C=0 than of C=C, C=C, C=N, or C N, so that selective reduction of the former—in the presence of any of the latter—cannot normally be achieved catalytically. This can, however, be done with various, usually complex, metal hydrides. 

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