The main examples involving the replacement of an oxo group by two hydrogen atoms (A=O → AH2) are hydrogenolysis. Typical examples use metal catalysts and H2 as the reagent. Conditions are typically more forcing than hydrogenation.[citation needed]
Deoxygenation is an important goal of the conversion of biomass to useful fuels and chemicals. Partial deoxygenation is effected by dehydration and decarboxylation.[1]
Other routes
Oxygen groups can also be removed by the reductive coupling of ketones, as illustrated by the McMurry reaction.
Phosphorus occurs in nature as oxides, so to produce elemental form of the element, deoxygenation is required. The main method involves carbothermic reduction (i.e., carbon is the deoxygenation agent).
4 Ca5(PO4)3F + 18 SiO2 + 30 C → 3 P4 + 30 CO + 18 CaSiO3 + 2 CaF2
Oxophilic main group compounds are useful reagents for certain deoxygenations conducted on laboratory scale. The highly oxophilic reagent hexachlorodisilane (Si2Cl6) stereospecifically deoxygenates phosphine oxides.[5][6]
S=O bonds
A chemical reagent for the deoxygenation of many sulfur and nitrogen oxo compounds is the combination trifluoroacetic anhydride/sodium iodide.[7] For example, in the deoxygenation of the sulfoxidediphenylsulfoxide to the sulfidediphenylsulfide:
The reaction mechanism is based on the activation of the sulfoxide by a trifluoroacetyl group and oxidation of iodine. Iodine is formed quantitatively in this reaction and therefore the reagent is used for the analytical detection of many oxo compounds.
^Sheldon, Roger A. (2014). "Green and sustainable manufacture of chemicals from biomass: state of the art". Green Chemistry. 16 (3): 950–963. doi:10.1039/C3GC41935E.
^Takuya Nakagiri; Masahito Murai; Kazuhiko Takai (2015). "Stereospecific Deoxygenation of Aliphatic Epoxides to Alkenes under Rhenium Catalysis". Org. Lett. 17 (13): 3346–3349. doi:10.1021/acs.orglett.5b01583. PMID26065934.
^Tsurugi, Hayato; Mashima, Kazushi (2019). "Salt-Free Reduction of Transition Metal Complexes by Bis(trimethylsilyl)cyclohexadiene, -dihydropyrazine, and -4,4′-bipyridinylidene Derivatives". Accounts of Chemical Research. 52 (3): 769–779. doi:10.1021/acs.accounts.8b00638. PMID30794373. S2CID73505603.
^David P. Sebesta "Hexachlorodisilane" in Encyclopedia of Reagents for Organic Synthesis John Wiley, London, 2001. doi:10.1002/047084289X.rh007 Article Online Posting Date: April 15, 2001.
^Podyacheva, Evgeniya; Kuchuk, Ekaterina; Chusov, Denis (2019). "Reduction of phosphine oxides to phosphines". Tetrahedron Letters. 60 (8): 575–582. doi:10.1016/j.tetlet.2018.12.070. S2CID104364715.
^Trifluoroacetic anhydride-sodium iodide reagent. Nature and applicationsArkivoc2007 (JE-2136MR) Zbigniew H. Kudzin, Marcin H. Kudzin, Józef Drabowicz, and Andrzej Kotyński Link