Deoxygenation of biobased molecules by decarboxylation and decarbonylation – a review on the role of heterogeneous, homogeneous and bio-catalysis

Abstract

Use of biomass is crucial for a sustainable supply of chemicals and fuels for future generations. Compared to fossil feedstocks, biomass is more functionalized and requires defunctionalisation to make it suitable for use. Deoxygenation is an important method of defunctionalisation. While thermal deoxygenation is possible, high energy input and lower reaction selectivity makes it less suitable for producing the desired chemicals and fuels. Catalytic deoxygenation is more successful by lowering the activation energy of the reaction, and when designed correctly, is more selective. Catalytic deoxygenation can be performed in various ways. Here we focus on decarboxylation and decarbonylation. There are several classes of catalysts: heterogeneous, homogeneous, bio-and organocatalysts and all have limitations. Homogeneous catalysts generally have superior selectivity and specificity but separation from the reaction is cumbersome. Heterogeneous catalysts are more readily isolated and can be utilised at high temperatures, however they have lower selectivity in complex reaction mixtures. While bio-catalysts can operate at ambient temperatures, the volumetric productivity is lower. Therefore it is not always apparent in advance which catalyst is the most suitable in terms of conversion and selectivity under optimal process conditions. Here we compare classes of catalysts for the decarboxylation and decarbonylation of biobased molecules and discuss their limitations and advantages. We mainly focus on the activity of the catalysts and find there is a strong correlation between specific activity (turn over frequency) and temperature for metal based catalysts (homogeneous or heterogeneous). Thus one is not more active than the other at the same temperature. Alternatively, enzymes have a higher turnover frequency but drawbacks (low volumetric productivity) should be overcome.

Upgrading Lignocellulosic Biomasses: Hydrogenolysis of Platform Derived Molecules Promoted by Heterogeneous Pd-Fe Catalysts

“…Among several chemistries and technologies, hydrogenolysis processes have gained a lot of attention since it allows the breaking of carbon-carbon and/or carbon-oxygen bonds in the presence of a hydrogen source [66][67][68]. One of the main drawbacks in hydrogenolysis, also known as "hydrodeoxygenation" if referred to C-O bond breaking, is concerning the hydrogen management due to the poor solubility of molecular H 2 that leads to a considerable safety hazard.…”

TEMPO‐Mediated Oxidative Deformylation of Aldehydes: Applications in the Synthesis of Polyketide Fragments

“…1 was subjected to the general method A of oxidative deformylation; purification by column chromatography (petroleum ether/ethyl acetate = 3:1); yield 2e (29 mg, 0.1 mmol, 65 %) as a colorless oil.…”

“…[1] Most commonly they are associated with transition-metal chemistry such as the oxidative decarbonylation of m-terphenyl isocyanide complexes of molybdenum and tungsten [2] or alkyl-Heck-type reactions in which precursor aldehydes are decarbonylated. [1] Most commonly they are associated with transition-metal chemistry such as the oxidative decarbonylation of m-terphenyl isocyanide complexes of molybdenum and tungsten [2] or alkyl-Heck-type reactions in which precursor aldehydes are decarbonylated.…”

“…after Dess-Martin oxidation; crude aldehyde 1h was subjected to the general method B of oxidative deformylation; purification by column chromatography (petroleum ether/ethyl acetate = 5:1 to 3:1); yield 2h (50 mg, 0.12 mmol, 65 %, dr = 1.6:1) as a colorless oil.Major diastereoisomer 2h:1 H NMR (400 MHz, CDCl 3 , CHCl 3 = 7.26 ppm): δ = 7.36-7.18 (m, 5 H, aromatic H), 4.70 (d, J = 4.2 Hz, 1 H, 1-H), 3.99 (m, 1 H, 2-H), 3.92 (m, 1 H, CHOH), 1.80 (m, 1 H, HCH), 1.72 (m, 1 H, HCH), 1.48-1.38 (m, 2 H, HCH),1.16 (d, J = 6.4 Hz, 3 H,CH-CH 3 ), 1.15, 1.13, 1.09, 1.01 (4s, 12 H, 4 × CH 3 ), 0.9 (s, 9 H, tBu), 0.07 [s, 3 H. Si(CH 3 )], -0.16 [s, 3 H, Si(CH 3 )] ppm. HRMS(ESI): m/z: calculated for C 39 H 66 N 1 O 4 Si 1 [M + H + ]: 668.4530, found 668.4521.…”

Synthesis of γ‐Valerolactone from Carbohydrates and its Applications

“…In addition, biomass can also maintain the carbon balance as the emitted CO 2 in the Earth's atmosphere can be reconverted into biomass through photosynthesis . Currently, there is an intense research activity on the production of platform chemicals and fuels from biomass …”