Furfural offers a promising, rich platform for lignocellulosic biofuels. These include methylfuran and methyltetrahydrofuran, valerate esters, ethylfurfuryl and ethyltetrahydrofurfuryl ethers as well as various C(10)-C(15) coupling products. The various production routes are critically reviewed, and the needs for improvements are identified. Their relative industrial potential is analysed by defining an investment index and CO(2) emissions as well as determining the fuel properties for the resulting products. Finally, the most promising candidate, 2-methylfuran, was subjected to a road trial of 90,000 km in a gasoline blend. Importantly, the potential of the furfural platform relies heavily on the cost-competitive production of furfural from lignocellulosic feedstock. Conventional standalone and emerging coproduct processes-for example, as a coproduct of cellulosic ethanol, levulinic acid or hydroxymethyl furfural-are expensive and energetically demanding. Challenges and areas that need improvement are highlighted. In addition to providing a critical review of the literature, this paper also presents new results and analysis in this area.

Novozym 435-catalyzed ring-opening of a range of omega-methylated lactones demonstrates fascinating differences in rate of reaction and enantioselectivity. A switch from S- to R-selectivity was observed upon going from small (ring sizes or=8). This was attributed to the transition from a cisoid to a transoid conformational preference of the ester bond on going from small to large lactones. The S-selectivity of the ring-opening of the small, cisoid lactones was low to moderate, while the R-selectivity of the ring-opening of the large transoid lactones was surprisingly high. The S-selectivity of the ring-opening of the small, cisoid lactones combined with the established R-selectivity of the transesterification of (aliphatic) secondary alcohols prevented polymerization from taking place. Ring-opening of the large, transoid lactones was R-selective with high enantioselectivity. As a result, these lactones could be polymerized, without exception, by straightforward kinetic resolution polymerization, yielding the enantiopure R-polyester with excellent enantiomeric excess (>99%).

Iterative tandem catalysis is presented as a flexible tool for obtaining chiral macromolecules from racemic or prochiral monomers. Here, we combine lipase-catalyzed ring-opening of omega-substituted lactones with ruthenium-catalyzed racemization. In a two-pot system, enantioenriched oligomers of 6-methyl-epsilon-caprolactone were synthesized, which could not have been obtained by enzymatic ring-opening alone. A one-pot experiment proved highly promising in developing a novel route toward enantiopure polyesters.

Reaction of RuH 2 CO(PPh 3 ) 3 with tetrafluorosuccinic acid at 100°C gave rise to the formation of the dinuclear bis(tetrafluorosuccinate)-bridged Ru(II) complex 2, containing two water ligands. Exchange of the PPh 3 in complex 2 with various diphosphine ligands afforded a series of analogous complexes 3. Reaction of the latter with 1-phenylethanol at 130°C or with 2-propanol/Et 3 N at room temperature furnished the dinuclear dihydrido-bridged Ru(II) complexes 4. Complexes 2 and 4 were characterized by X-ray diffraction analysis. Both bis(tetrafluorosuccinate)-bridged complexes 3 and dihydrido-bridged complexes 4 catalyze the acceptorless dehydrogenation of 1-phenylethanol to acetophenone and dihydrogen with good yields and excellent selectivity under relatively mild conditions in the absence of acid or base. A tentative catalytic cycle for the dehydrogenation of secondary alcohols by Ru(II) complexes of type 3 is presented.