Sulfide catalysts reaction pathway

In conclusion, an extensive literature is available on the reaction networks that are thought to operate in HD,S of various types of thiophenic molecules besides the great advances that have been made in direct studies on molybdenum sulfides and related catalysts, this is another area in which organometallic chemistry has made an impressive contribution to HD,S catalysis, as a number of reaction pathways and mechanisms for the hydrogenation and hydrogenolysis of thiophenes on metal complexes in solution has been well established with the aid of a variety of physical techniques. 

The HDN network of MCHA is shown in Figure 1. Even though the HDN of amines is generally considered to be quite simple, there are still two reaction pathways in the HDN of MCHA over (fluorinated) sulfided NiMo/Al203 catalysts elimination of NH3 fi-om MCHA to... 

The regiochemical outcomes, thus, are strong indicatives for the reaction pathways the formation of linear alkenyl sulfides via a radical-mediated reaction pathway and the branched alkenyl sulfides via an insertion of alkyne into an M S bond. An interesting complementary selectivity between Tp Ph(PPh3)2 and Wilkinson s catalysts has been observed in the hydrothiolation of alkyl thiols, where a migratory Rh-H insertion pathway 17 was proposed (Scheme 46.4). 

Allyldiethylamine behaves similarly, but the yields are low since neither the starting amine nor the products are stable to the reaction conditions. For the efficiency of the cyclopropanation of the allylic systems under discussion, a comparison can be made between the triplet-sensitized photochemical reaction and the process carried out in the presence of copper or rhodium catalysts whereas with allyl halides and allyl ethers, the transition metal catalyzed reaction often produces higher yields (especially if tetraacetatodirhodium is used), the photochemical variant is the method of choice for allyl sulfides. The catalysts react with allyl sulfides (and with allyl selenides and allylamines, for that matter) exclusively via the ylide pathway (see Section 1.2.1.2.4.2.6.3.3. and Houben-Weyl, Vol. E19b, pll30). It should also be noted that the purely thermal decomposition of dimethyl diazomalonate in allyl sulfides produces no cyclopropane, but only the ylide-derived product in high yield.Very few cyclopropanes have been synthesized by photolysis of other diazocarbonyl compounds than a-diazo esters and a-diazo ketones, although this should not be impossible in several cases (e.g. a-diazo aldehydes, a-diazocarboxamides). Irradiation of a-diazo-a-(4-nitrophenyl)acetic acid in a mixture of 2-methylbut-2-ene and methanol gave mainly l-(4-nitrophenyl)-2,2,3-trimethylcyclo-propane-1-carboxylic acid (19, 71%) in addition to some O-H insertion product (10%). ... 

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