Hydrogenation/hydrogenolysis linkages

Reduction of low-spin Fe(m) imide 165 with hydrogen (1 atm, 20 °C) proceeds stepwise leading first to anilido complex 168 and then to 77-cyclohexadienyl complex 169 via hydrogenolysis of the Fe=NR linkage (Scheme 64). It should be mentioned that the similar low-spin cobalt complex [PhB(CH2PPh2)3]Co N-/>-Tol is stable to hydrogen pressure (1-3 atm) up to 70 °C <2004JA4538>. 

Flavone (2-phenylchromone) (68) is more labile to hydrogenolysis at the ether linkage than are 2-alkylchromones because it may be considered to be a benzyl-phenyl-type ether. Hydrogenation of flavone over copper-chromium oxide at 140-150°C gave 4-flavanol in a maximum yield of 65% in a very rapid reaction (8 min), while the flavanol was obtained in a yield of 85% in rapid hydrogenation of flavanone (69) at 135-145°C or in a yield of 93% in the hydrogenation in a dilute ethanol solution at 120-135°C (eq. 12.123).233... 

MPa H2, 1-cyclopropylethanol was obtained in 90% yield. Over Raney Ni, a mixture of 1-cyclopropylethanol and 2-pentanol was formed (eq. 13.147).288 Mitsui et al. studied the hydrogenolysis of l-phenylbicyclo[4.1.0]heptane (95) over Raney Ni, palladium black, Pd-C, Rh-C, and platinum oxide in ethanol at 25°C and atmospheric hydrogen pressure (eq. 13.148).289 Hydrogenolysis of 95 at the C1-C7 linkage gave... 

The hydrogenolysis of N-N linkages is involved in the hydrogenation of such compounds as hydrazines, azines, hydrazones, azo compounds, or azides. Usually, palladium, platinum, and nickel catalysts are used for the hydrogenolysis of these compounds (see Chapters 8 and 9). Palladium catalysts are known to be particularly effective for the hydrogenolysis of aromatic hydrazo compounds.317... 

The hydrogenolysis of 0-0 linkages is involved in the hydrogenation of peroxides, hydroperoxides, and ozonides. Decomposition may occur catalytically in the absence of hydrogen, as was observed in as early as 1818 by Thenard with hydrogen peroxide in the presence of platinum. 

Hydrogenolysis and Hydrogenation Reactions 6.5.3.1 Cleavage of lnterumtary Linkages... 

Flindersine and a new quinolone alkaloid, 3-dimethylallyl-4-dimethyl-allyloxy-2-quinolone, C19H23O2N (mp 114°-115°) were isolated. Mass and NMR spectroscopy indicated structure LXVIIa for this base. Minor chemical reactions served to confirm this structure, particularly catalytic hydrogenation, which induced rapid hydrogenolysis of the ether linkage 102). 

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