Catalytic hydrogen generation

H2 serves as the alternative energy source relative to fossil fuels and biomass [181] because it is clean and environmentally friendly. Hence, catalytic hydrogen generation from water under mild conditions is one of the goals for the organometallic catalysis. One of the hopeful methods is the electrochemical reduction of protons by a hydrogenase mimic. 

Catalytic Hydrogen Generation from Organic Chemical... 

Catalytic Hydrogen Generation from Organic Chemical Hydrides under Superheated Liquid-Film Conditions by Use of Laboratory-Scale Continuous Reactor... 

Lasiodine-A (59) (33), though not a cyclic peptide, exhibits many of the structural features common to that class and could conceivably result from subsequent scission of a cyclic precursor (4). Spectral study identified an isopropylidene, a secondary hydroxyl, a phenolic hydroxyl, and an ester function. Mass spectra fail to reveal the molecular ion but a fragment of mass M-I06 as known from some other peptide alkaloids containing phenylserine as ring bond amino acid (30,31,62). Catalytic hydrogenation generates N-methylvaline and a moiety (83) whose structure was deduced from spectral studies and from hydrolytic degradations. Reduction of the alkaloid with lithiumaluminiumhydride... 

M. Calahan, Thermo-catalytic hydrogen generation from hydrocarbon fuels. From Electrocatalysis to Fuel Cells. G. Sanstede, ed., Battelle Seattle Research Center (1972)... 

Their more directed approach to hirsutic acid utilized 341 as starting material (Scheme 53).335 This diketo ester was the major product obtained from alkylation of the pyrrolidine enamine of340 with 3-bromo-2-butanone and aldolization in aqueous base. Reesterification with diazomethane and catalytic hydrogenation generated the cis-fused bicyclooctane nucleus. The subsequent Claisen alkylation of 342 proved to be stereoselective, affording 343 as the major product. Cyclization as before furnished 344 whose further transformations are currently being examined. 

Agrell, J., Lindstrom, B., Pettersson, L., and Jaras, S. Catalytic hydrogen generation from methanol. Catalysis, 2002, 16, 67. 

Masaru Watanabe, Hiroshi Inomata, Kunio Aral. (2002). Catalytic hydrogen generation from biomass (glucose and cellulose) with ZrO2 in supercritical water. 22, 405-410. 

The quinic acid derived 2,5,6-trideoxystreptamine analogs 61 was used to prepare 5,6-dideoxyneamine (62) hiosynthetically from Streptomyces fradiae [49]. The crucial intermediate for synthesis of 61 was the hydroxyketone 55, which is readily available from quinic acid. Treatment of 55 with p-toluenesulfonyl chloride in pyridine gave enone 56, which after catalytic hydrogenation generated the saturated ketone 57. Stereoselective reduction of 57, followed by tosylation, furnished deriv-... 

A new pyrrolidine amide, trichonine (C24H23ON mp 65-67°) has been isolated from this plant. Its structure (174) was arrived at primarily by mass and NMR spectroscopy. Catalytic hydrogenation generated the expected tetrahydro derivative (mp 38-50°) and hydrolysis afforded eicosanoic acid and pyrrolidine. Finally, a synthetie specimen was prepared by reacting eicosanoyl chloride with pyrrolidine (209). 

For the large-scale use of H2 gas in mobile, distant, and small size applications, supplementary steps (packaging, distribution, storage, transfer) are areas in need of development. To fulfil these requirements, an onsite homogeneous catalytic hydrogen generation process will need to be developed, improved, and applied. In the future hydrogen economy, a suitable onsite supply will be a necessity. 

Haplophyllidine, C18H23O4N (mp 111° [a] p —16°) monoacetyl (mp 148°), has one hydroxyl and two methoxyls. Catalytic hydrogenation generates a tetrahydro derivative, C18H27O4N (mp 136° [a] — 81°), indicative of two double bonds. Warming with 25% sulfuric acids forms a base, C16H19O3N ( ) (mp 125°-127°). The UV-spectrum of haplophyllidine resembles that of quinoline (215). 

Although considered an active participant in the process cycle, the tetrahydroaLkylanthraquinone (10) may not be a significant part of the catalytic hydrogenation because, dependent on the concentration in the working solution, these could all be converted to the hydroquinone by the labile shift per equation 17 and not be available to participate. None of the other first- or second-generation anthraquinone derivatives produce hydrogen peroxide, but most are susceptible to further reaction by oxidative or reductive mechanisms. 

Abstract Organic syntheses catalyzed by iron complexes have attracted considerable attention because iron is an abundant, inexpensive, and environmentally benign metal. It has been documented that various iron hydride complexes play important roles in catalytic cycles such as hydrogenation, hydrosilylation, hydro-boration, hydrogen generation, and element-element bond formation. This chapter summarizes the recent developments, mainly from 2000 to 2009, of iron catalysts involving hydride ligand(s) and the role of Fe-H species in catalytic cycles. 

Healey, T, Thomson, W. J., Catalytic micro-reactor systems for hydrogen generation, in Matlosz, M., Ehreeld,... 

Catalytic hydrogenations are generally highly selective with almost quantitative yield (Rylander, 1979 Augustine, 1976). As the metals are recovered from spent catalysts, essentially no non-combustible waste is generated. 

Catalytic hydrogenation transfers the elements of molecular hydrogen through a series of complexes and intermediates. Diimide, HN=NH, an unstable hydrogen donor that can be generated in situ, finds specialized application in the reduction of carbon-carbon double bonds. Simple alkenes are reduced efficiently by diimide, but other easily reduced functional groups, such as nitro and cyano are unaffected. The mechanism of the reaction is pictured as a concerted transfer of hydrogen via a nonpolar cyclic TS. 

A similar strategy served to carry out the last step of an asymmetric synthesis of the alkaloid (—)-cryptopleurine 12. Compound 331, prepared from the known chiral starting material (l )-( )-4-(tributylstannyl)but-3-en-2-ol, underwent cross-metathesis to 332 in the presence of Grubbs second-generation catalyst. Catalytic hydrogenation of the double bond in 332 with simultaneous N-deprotection, followed by acetate saponification and cyclization under Mitsunobu conditions, gave the piperidine derivative 333, which was transformed into (—)-cryptopleurine by reaction with formaldehyde in the presence of acid (Scheme 73) <2004JOC3144>. 

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