Involving Reduction

The cleavage of 1-bora-adamantane by bromine is a route to other interesting cage compounds.  

Miscellaneous.—2-Trimethylsilylmethyl-l,3,2-dioxaborolanes (7) may be formed by reaction of the 2-alkyl analogues (8) with lithiated chloromethyl(trimethyl)-silane, and may be further converted into 2-alkenyl derivatives (9), at least for the case of R=H.  

Allyltin derivatives have been used for preparation of allyl(dialkoxy)boranes, apparently without concomitant rearrangement of the allyl moiety during reaction. Lithium tetrakis(trimethylsilyl)borate has been prepared, using tri-methylsilyl-lithium as reagent.  

The addition of so-called methylborylene to alkynes gives a dimeric product (10), in contrast to the monomeric boracyclopropanes previously claimed for reaction of the same species with alkenes. Doubts about the characterization of the latter species do not appear to have been satisfactorily answered, and it does not yet appear justifiable to insist that the reactions occur through the intermediacy of MeB , although this is clearly one possibility. The radical anion of a borabenzene (11) has been obtained by treatment of 1,4-difluoro-2,3,5,6-tetramethyl-l,4-diboracyclohexa-2,5-diene with potassium metal. There are two independent reports of the preparation of the first examples of the interesting class of compounds (12), tetra-alkyldiboranes(4). Both utilize bulky tertiary butyl groups to stabilize the products. 

The preparation of ammonia-carboxyborane (H3N.BH2CO2H) from the corresponding trimethylamine adduct has been reported. The compound shows antihyperlipidemic and antitumour activity. 

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Analysis Our methods for making 1,2-dioxygenated compounds (frames 154-157) involve reductive linking of a dicarbonyl compound ... 

Methamphetannne is a notorious street drug One synthesis involves reductive amination of benzyl methyl ketone with methylamine What is the structure of methamphetamine ... 

The cathode reaction involves reduction of silver oxide to metallic silver [7440-22-4J. The reaction is a two-phase, heterogeneous reaction producing a substantially constant voltage during discharge. Some manganese dioxide may be added to the cathode, as in the case of mercury oxide cells. 

Redistillation. For certain appHcations, especially those involving reduction of other metal compounds, better than 99% purity is required. This can be achieved by redistillation. In one method, cmde calcium is placed in the bottom of a large vertical retort made of heat-resistant steel equipped with a water-cooled condenser at the top. The retort is sealed and evacuated to a pressure of less than 6.6 Pa (0.05 mm Hg) while the bottom is heated to 900—925°C. Under these conditions calcium quickly distills to the condensing section leaving behind the bulk of the less volatile impurities. Variations of this method have been used for commercial production. Subsequent processing must take place under exclusion of moisture to avoid oxidation. 

One of the first practical methods for the manufacture of cinnamyl alcohol involved reduction of cinnamic aldehyde diacetate with iron filings in acetic acid. This approach suffered from low yields and Hberation of a significant amount of the starting aldehyde. 

Benzidine chemistry involves reduction. The nitro precursor is reduced either by zinc and alkali or electrolyticaUy to the hydrazo intermediate, which is then transformed to the benzidine by treatment with acid. 

An oxidative cyclization, (151) -> (152), with azodicarboxylate (78CC764) is balanced by the synthesis of 5-deazaalloxazines from aryl bis(6-aminouracilyl)methanes, which involves azodicarboxylate in an intermediate electrophilic capacity (153 -> 154) (79CPB2507). Other methods involve reductive cyclizations (72AP751). 

Some further transformations involving reduction of the 3-carboxylic acid group are shown in Scheme 21 (66JOC1922, 64JMC483, 70JMC389). 

Alternatives to Arresters Alternatives to the use of flame arresters include fast-ac ting isolation valves, vapor suppression systems, velocity-type devices in which gas velocity is designed to exceed flashback velocity, and control of the flammable mixture (NFPA 69 standard, Explosion Prevention Systems ). The latter alternative frequently involves reduction of oxygen concentration to less than the limiting oxygen concentration (LOC) of the gas stream. 

As Table 15.1 indicates, reactions leading to alcohols are not in short supply. Nevertheless, several more will be added to the list in the present chapter—testimony to the importance of alcohols in synthetic organic chemistry. Some of these methods involve reduction of car bonyl groups ... 

FIGURE 21.V The fatty acyl-CoA dehydrogenase reaction, emphasizing that the reaction involves reduction of enzyme-bonnd FAD (indicated by brackets). 

A common modification of the Bischler-Napieralski reaction involves reduction of the dihydroisoquinoline product 2 to provide a tetrahydroisoquinoline derivative 19. A variety of different reducing agents have been employed, with NaBHi used with the greatest frequency. In many cases the reduction is carried out on the crude product of the Bischler-Napieralski reaction purification of the dihydroisoquinoline prior to reduction is usually not necessary. 

Important pathways for biologic deactivation of cortical steroids in humans involve reduction of the ketone at 21 and scision of the entire side chain at C17. Substitution at Cie, it... 

An excellent method for producing methyl indole-4-carboxylate from commercially available 3-nitro-2-methylbenzoic acid involves reduction of an intermediate nitroenamine (57). 

Treatment of hydrazino-compounds with iodine in chloroform can afford iodides which are convertible into methylene derivatives (7,8). An extension of this approach currently being investigated involves reduction of the hydrazones obtainable from glycopyranosiduloses and treatment of the products with iodine. 

The Mecrwein-Ponndoi f-Verlev reaction involves reduction of a ketone by treatment with an excess of aluminum triisopropoxide. The mechanism of the process is closely related to the Cannizzaro reaction in that a hydride ion acts as a leaving group. Propose a mechanism. 

Some reactions of PtMe4L2 systems do not involve reductive elimination thus reaction of PtMe4(NN) (NN = phen, bipy) with organic acids yielding PtMe3A(NN) (A = formate, acetate, benzoate, salicylate) is first order in both reactants [201]. 

The influence of the presence of sulfur adatoms on the adsorption and decomposition of methanol and other alcohols on metal surfaces is in general twofold. It involves reduction of the adsorption rate and the adsorptive capacity of the surface as well as significant modification of the decomposition reaction path. For example, on Ni(100) methanol is adsorbed dissociatively at temperatures as low as -100K and decomposes to CO and hydrogen at temperatures higher than 300 K. As shown in Fig. 2.38 preadsorption of sulfur on Ni(100) inhibits the complete decomposition of adsorbed methanol and favors the production of HCHO in a narrow range of sulfur coverage (between 0.2 and 0.5). 

Testosterone is metaboHzed by two pathways. One involves oxidation at the 17 position, and the other involves reduction of the A ring double bond and the 3-ketone. Metabohsm by the first pathway occurs in many tissues, including liver, and produces 17-ketosteroids that... 

The mechanism is believed to be a two-step process involving reduction and oxidation of the copper center ... 

The aerobic biodegradation of monocyclic azaarenes frequently involves reduction (Chapter 10, Part 1), but purely chemical reduction may take place under highly anaerobic conditions. This has been encountered with the substituted l,2,4-triazolo[l,5a]pyrimidine (Flumetsulam) (Wolt et al. 1992) (Figure 1.27). 

The anaerobic degradation of some hydroxybenzoates and phenols involves reductive removal of the phenolic hydroxyl group. The enzyme that dehydroxylates 4-hydroxybenzoyl-CoA in Thauera aromatica is a molybdenum-flavin-iron-sulfur protein (Breese and Fuchs 1998), and is similar to the enzyme from the nonsulfur phototroph Rhodopseudomonas palustris that carries out the same reaction (Gibson et al. 1997). 

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