Benzene addition reduction

The highly reactive cadmium can be prepared by two different methods. One approach is a room temperature reduction of CdC with lithium naphthalide in THF or DME. The second approach allows the preparation of the reactive metal in a hydrocarbon solvent. First, lithium naphthalide is prepared in benzene addition of this solution to CdC produces a highly reactive cadmium powder. 

Fully oxidized vanadia is a poor, nonselective catalyst for benzene oxidation. Reduction to lower oxides brings about a large increase in catalytic activity and some improvement in selectivity. Substantial enhancement of selectivity can be achieved by the addition of molybdena,1009 reaching a maximum at a M0O3 content of about 30%. Promoters (Ag, Ti, Ni, Co) lead to further improvements.1006... 

Air (CDDs) Drawing of approximately 325 m3 of air through quartz fiber filter/polyurethane foam Soxhlet extraction with benzene, volume reduction clean-up using silica, alumina, activated carbon volume reduction addition of [13C12]2,3,7,8-TCDD. HRGC/HRMS MID (EPA TO-9) 1-5 pg/m3 68-140 from ultra pure, filtered air EPA1988g... 

An oxidative route to 1,3-thiazoles (39) and oxazoles, which bear the requisite functionality, such as amino groups and stereocenters, for incorporation into a variety of natural products was reported. Treatment of 1,3-thiazolines (36) with CuBr (l.leq), Cu(OAc)2 (l.leq) and t-butyl perbenzoate (1.5eq) under benzene reflux gave 1,3-thiazoles (39) in about 80% yield. A plausible mechanism included generation of a Cu (III) species (37) via oxidative addition, reductive elimination to the acyloxy thiazoline (38), and syn elimination on warming to produce the thiazole (39). [94TL6803]... 

The reduction products from triphenylsulfonium ions depend on the electrode material and the potential [116-118]. Electrolysis of tirphenylsulfonium bromide at a mercury electrode at the potential of the first wave quantitatively yields diphenylsulfide and diphe-nylmercury. No benzene or diphenyl is formed. At potentials more negative than the second reduction wave, diphenylsulfide and benzene are formed quantitatively, provided low substrate concentrations are used. With increasing substrate concentration the yield of diphenylmercury increases at the expense of benzene. Reduction in aqueous solution at an aluminum cathode produces diphenylsulfide and some benzene addition of DMF increases the yield of benzene, as DMF is as a better hydrogen atom donor than water [117]. 

Evidence for alkane activation has also been seen by the observation of H/D exchange between two alkanes, an alkane and an arene, or an alkane and THE Using CpRe(PPh3)2H2 as the photo catalyst, thousands of turnovers have been observed. While the intermediate responsible for this catalysis was not identified, it does not appear to be [CpRe(PPh3)H2] undergoing Rem/Rev oxidative addition/reductive elimination, since no deuterium incorporation was observed in the dihydride catalyst [99]. Several other metal hydrides are known to catalyze H/D exchange between alkanes and deuterated benzene, such as Ir(PMe3)2H5 [100],CpMo(dmpe)H3 [101], and Re[P(c-hexyl)3]2H7 [102]. 

Table III also shows that hydrogen and the chlorinated butanes are reduced substantially when ethyl chloride is irradiated in the presence of benzene. The other products are essentially unaffected by this additive. In the radiolysis of certain alkanes (4), benzene, added in small amounts, does not interfere with the fast ion-molecule reactions of primary ionic fragments or with free radical processes, but it will efficiently condense unreactive or long-lived ions in the system. It is reasonable to assume that this is also true for alkyl halide systems and that the reduction in product yields compared with the pure compound upon adding benzene may be attributed to the interception of unreactive ions. Since the rate constants for reactions of the expected primary ions with ethyl chloride are very large (see Table II), the concentration of benzene used in our experiments should not interfere with the initial fast ion-molecule reactions. For ethyl chloride ion-molecule reactions, C4Hi0C1+ is the only unreactive ion of appreciable abundance which is expected in this system at the elevated pressures used in the radiolysis experiments. Thus, the reduced product yields in the presence of benzene additive can be identified tentatively with the removal of this stable ion and the elimination of its resultant neutralization products.

Our synthesis began with the (4+3)-cycloaddition between diene 180 and 2,5-dibromocyclopentanone (65, Scheme 7.41). This reaction was unique in that we used only a stoichiometric amount of diene and employed benzene as a co-solvent with trifluoroethanol. The adduct 181 was obtained in very good yield, especially given that we had used a stoichiometric amount of diene. The quasi-Favorskii sequence, initiated by LAH reduction of the ketone, included an additional reduction of the resulting aldehyde 182 to give alcohol 183. Dehydroxylation was accomplished by conversion to the corresponding iodide followed by... 

In contrast to this report, a surprising result was obtained by Chen and co-workers by studying with electrospray tandem mass spectrometry the C-H activation in -pentane, cyclohexane, and benzene by Bergman s catalyst [Cp Ir(PMe3)Me]. Neither the oxidative addition/reductive elimination nor the concerted cr-bond metathesis mechanism was found to be operative. Rather, an elimination/addition mechanism through Ir(m) intermediates was proposed and confirmed by isotopic labeling. 

Reduction of a nitro compound to a primary amine. In a 50 ml. round-bottomed or conical flask fitted with a reflux condenser, place 1 g. of the nitro compound and 2 g. of granulated tin. Measure out 10 ml. of concentrated hydrochloric acid and add it in three equal portions to the mixtiue shake thoroughly after each addition. When the vigorous reaction subsides, heat under reflux on a water bath until the nitro compound has completely reacted (20-30 minutes). Shake the reaction mixture from time to time if the nitro compound appears to be very insoluble, add 5 ml. of alcohol. Cool the reaction mixture, and add 20-40 per cent, sodium hydroxide solution imtil the precipitate of tin hydroxide dissolves. Extract the resulting amine from the cooled solution with ether, and remove the ether by distillation. Examine the residue with regard to its solubility in 5 per cent, hydrochloric acid and its reaction with acetyl chloride or benzene-sulphonyl chloride. 

Krapcho and Bothner-By made additional findings that are valuable ii understanding the Birch reduction. The relative rates of reduction o benzene by lithium, sodium and potassium (ethanol as proton donor) wer found to be approximately 180 1 0.5. In addition, they found that ben zene is reduced fourteen times more rapidly when methanol is the protoi donor than when /-butyl alcohol is used. Finally, the relative rates of reduc tion of various simple aromatic compounds by lithium were deteiTnined these data are given in Table 1-2. Taken together, the above data sho that the rate of a given Birch reduction is strikingly controlled by the meta... 

Estrone methyl ether (100 g, 0.35 mole) is mixed with 100 ml of absolute ethanol, 100 ml of benzene and 200 ml of triethyl orthoformate. Concentrated sulfuric acid (1.55 ml) is added and the mixture is stirred at room temperature for 2 hr. The mixture is then made alkaline by the addition of excess tetra-methylguanidine (ca. 4 ml) and the organic solvents are removed. The residue is dissolved in heptane and the solution is filtered through Celite to prevent emulsions in the following extraction. The solution is then washed threetimes with 500 ml of 10 % sodium hydroxide solution in methanol to remove excess triethyl orthoformate, which would interfere with the Birch reduction solvent system. The heptane solution is dried over sodium sulfate and the solvent is removed. The residue is satisfactory for the Birch reduction step. Infrared analysis shows that the material contains 1.3-1.5% of estrone methyl ether. The pure ketal may be obtained by crystallization from anhydrous ethanol, mp 99-100°. Acidification of the methanolic sodium hydroxide washes affords 10-12 g of recovered estrone methyl ether. 

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