The conversion of biomass into fuels and chemical feedstocks is one part of a drive to reduce the world's dependence on crude oil. For transportation fuels in particular, wholesale replacement of a fuel is logistically problematic, not least because of the infrastructure that is already in place. Here, we describe the catalytic defunctionalization of a series of biomass-derived molecules to provide linear alkanes suitable for use as transportation fuels. These biomass-derived molecules contain a variety of functional groups, including olefins, furan rings and carbonyl groups. We describe the removal of these in either a stepwise process or a one-pot process using common reagents and catalysts under mild reaction conditions to provide n-alkanes in good yields and with high selectivities. Our general synthetic approach is applicable to a range of precursors with different carbon content (chain length). This allows the selective generation of linear alkanes with carbon chain lengths between eight and sixteen carbons.

The aerobic oxidation of a phenolic lignin model compound with a vanadium catalyst results in the oxidative cleavage of the C-C bond between the aryl ring and the adjacent hydroxy-substituted carbon atom. Labeling experiments indicate key mechanistic differences to a previously reported related C-O bond cleavage reaction. The selectivity in C-C versus C-O bond cleavage depends on the choice of the vanadium catalyst.

Non-food based biomass (lignocellulose) is an attractive renewable carbon feedstock for the production of chemicals or fuels. Lignin, a key constituent (15À30%) of lignocellulose, is an irregular polymer composed of methoxy-substituted phenyl and phenolic subunits. 1,2 Because of its structural complexity and inherent resistance to chemical reactivity, lignin has been considered a major obstacle in the production of biofuels from lignocellulose.Recently, increasing attention has been focused on the development of methods to convert lignin into more valuable and useful products. 3,4 Reductive approaches using hydrogen or formic acid have been developed to transform lignin into mixtures of monomeric phenols and alkanes suitable for use as fuel additives. 5À9 Catalytic oxidation of lignin using environmentally friendly oxidants (O 2 , H 2 O 2 ) has also been explored as a means to break lignin down into monomeric products. 10À15 Crestini, Chen, Dolphin, and others have investigated the oxidation of lignin and lignin model compounds using H 2 O 2 and transition metal catalysts, including Mn and Fe complexes of porphyrin and TACN ligands (TACN = triazacyclononane). 16À21 While the reduction of lignin is well suited for the production of fuels, aerobic oxidation is advantageous in that it requires no added reagents and could preserve a high degree of the functionality present in the original lignin polymer.Oxidation is also the primary pathway by which lignin is broken down in nature. Both the enzymes lignin peroxidase and manganese-dependent peroxidase are thought to mediate the oxidative disassembly of lignin by wood-rotting fungi. 22À24 To establish the mechanisms of these enzymes, detailed studies have been carried out of the oxidation of arylglycerol β-aryl ether compounds, 25À28 which are models for the lignin β-O-4 linkage, a predominant structural feature representing approximately 50% of the linkages occurring in the natural polymer. 29 For example, oxidation of lignin model compound 1-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)propane-1,3-diol (1) (Scheme 1) by lignin peroxidase affords products resulting from cleavage of the

The reactivity of homogeneous oxovanadium and copper catalysts toward aerobic oxidation of phenolic and nonphenolic β-1 lignin model compounds has been investigated. Aerobic oxidation of diastereomeric, nonphenolic β-1 lignin models (1T, 1E) using the sixcoordinate vanadium complex (HQ) 2 V V (O)(O i Pr) (HQ = 8-oxyquinolinate) as a precatalyst in pyridine afforded ketone (3) and dehydrated ketone (4) derived from oxidation of the secondary alcohol. In contrast, using CuOTf/2,6-lutidine/TEMPO (OTf = trifluoromethanesulfonate, TEMPO = 2,2,6,6-tetramethyl-piperidin-1-yl-oxyl) in toluene for the same reaction afforded 3,5dimethoxybenzaldehyde ( 5) and 4-methoxybenzaldehyde (6) as major products resulting from C α −C β bond cleavage. Reactions of the corresponding phenolic lignin model compounds (2T, 2E) with 10 mol % CuOTf/2,6lutidine/TEMPO gave ketone (9) as the major product, whereas 10 mol % (HQ) 2 V V (O)(O i Pr) or a stoichiometric amount of CuOTf/2,6-lutidine/TEMPO yielded 2,6-dimethoxybenzoquinone (10) as the major product, arising from cleavage of the C aryl − C α bond. Different selectivity was observed in the oxidation of 2T, 2E using the five-coordinate complex (dipic)V V (O)(O i Pr) (dipic = dipicolinate), with α,β-unsaturated aldehyde ( 14) as the major product (formed from oxidation of the primary alcohol and dehydration). The key differences in chemoselectivity between the vanadium and copper catalysts in the oxidations of these phenolic and nonphenolic β-1 lignin models are discussed.

Transition metal-catalyzed aerobic alcohol oxidation is an attractive method for the synthesis of carbonyl compounds, but most catalytic systems feature precious metals and require pure oxygen. The vanadium complex (HQ)(2)V(V)(O)(O(i)Pr) (2 mol %, HQ = 8-quinolinate) and NEt(3) (10 mol %) catalyze the oxidation of benzylic, allylic, and propargylic alcohols with air. The catalyst can be easily prepared under air using commercially available reagents and is effective for a wide range of primary and secondary alcohols.