Aromatic lead salts

The mechanism of the indolization of aniline 5 with methylthio-2-propanone 6 is illustrated below. Aniline 5 reacts with f-BuOCl to provide A-chloroaniline 9. This chloroaniline 9 reacts with sulfide 6 to yield azasulfonium salt 10. Deprotonation of the carbon atom adjacent to the sulfur provides the ylide 11. Intramolecular attack of the nucleophilic portion of the ylide 11 in a Sommelet-Hauser type rearrangement produces 12. Proton transfer and re-aromatization leads to 13 after which intramolecular addition of the amine to the carbonyl function generates the carbinolamine 14. Dehydration of 14 by prototropic rearrangement eventually furnishes the indole 8. 

Plateau burning characteristics are dependent on the chemical components and the nature of the catalysts. The effects of aromatic lead and copper salts on burning rate behavior are shown in Fig. 6.24. The addition of PbSa (1 %) increases the burn-... 

Inorganic lead compounds such as PbO, Pb02, Pb304, PbS, lead molybdate and lead perchlorate 2) Lead salts of organic adds such as 2,4-dihydroxy benzoic add, salicylic add, acetyl salicylic add and methoxy propionic add i) Effective with propellants of cal. val. less than 900 cal. g 1 ii) Lead salts of aromatic adds are effective with propellants of higher cal. val. [237]. 

Combination of lead and copper salts of aliphatic and aromatic carboxylic adds Extend mesa region compared with lead salts alone in propellants having cal. val. -600-1250calg 1 i.e., both cooler and hotter propellants [238, 239]. 

Triazenes have been prepared by the treatment of resin-bound aromatic diazonium salts with secondary amines (Figure 3.27). Regeneration of the amine can be effected by mild acidolysis (Entry 1, Table 3.23). Triazenes have been shown to be stable towards bases such as TBAF, potassium hydroxide, or potassium tert-butoxide [454], and under the conditions of the Heck reaction [455]. Primary amines cannot be linked to supports as triazenes because treatment of triazenes such as R-HN-N=N-Ar-Pol with acid leads to the release of aliphatic diazonium salts into solution [373]. Triazenes derived from primary amines can, however, be used for the preparation of amides and ureas (see Section 3.3.4),... 

Support-bound triazenes, which can be prepared from resin-bound secondary aliphatic amines and aromatic diazonium salts [455], undergo cleavage upon treatment with acids, leading to regeneration of the aromatic diazonium salts. In cross-linked polystyrene, these decompose to yield nitrogen and, preferentially, radical-derived products. If the acidolysis of polystyrene-bound triazenes is conducted in the presence of hydrogen-atom donors (e.g. THF), unsubstituted arenes can be obtained (Entries 8 and 9, Table 3.47). In the presence of alkenes or alkynes and Pd(OAc)2, the initially formed diazonium salts undergo Heck reaction to yield vinylated or alkynylated arenes (Entry 10, Table 3.47). Similarly, unsubstituted arenes can be obtained by oxida-... 

The adoption of an eluent having a very low conductivity, which can be passed directly through the conductometric detector. Typical eluents used are benzoate, phthalate, or other aromatic acid salts, with low limiting equivalent conductances (leading to direct detection) or potassium hydroxide eluent, with high conduc-... 

Coupling of aromatic diazonium salts with stabilized methylenephosphoranes leads to arylazometh-ylenephosphoranes (equation 30). ... 

Several groups earlier had demonstrated that even stabilized sulphonium ylides, e.g. phenacylides, would undergo 1,5-rearrangement. Baldwin and Erickson found that even the aromatic sulphonium salt (21), when treated with butyl-lithium at — 40 °C, would undergo 1,5-rearrangement leading to destruction of the aromatic system. 

The above reaction resembles previously mentioned preparation of Meisenheimer adducts by reaction of benzofuroxan with potassium carbonate in aqueous solution. It is interesting that using 7-chlorofuroxan instead of furoxan as a starting material, under otherwise similar conditions, leads to a nucleophilic aromatic substitution and formation of fully aromatic phenol salts. The same is true for furazans (Read, Personal Communication). 

The alkylation of aromatic nitro compoimds and of quinones has been accomplished by means of the radicals liberated by the decomposition of tetravalent lead salts of oi anic acids or of acyl peroxides, or by the electrolysis of sodium salts of organic acids. ... 

Metal oxides have been employed to catalyse the acylation of aromatics, leading to dimethylbenzophenones and 4-substituted benzophenones. The reaction of t-butylbenzene with benzoyl chloride in the presence of small amounts of ferric oxide leads to 4-t-butylbenzophenone. Substituted benzophenones have also been obtained by hydrolysis of the dilithium salts (68) formed by the reaction of lithium carboxylates with organolithium derivatives, and benzo-phenone-2 -methoxy-2-sulphinic acids (69) have been successfully prepared by displacement of the sulphone linkage in thioxanthen-9-one 10,10-dioxides (70)... 

To assert that the decomposition of the Meisenheimer intermediate 2 (step 2) is the rds in the case of o-toluidine requires being more precise, as fliis step is a little more complicated than what has been described in Scheme 33.3. The decomposition of 2 can follow two alternative pathways that are indicated in Scheme 33.4. The first alternative (path a) is a base-catalyzed decomposition process, which consists of the fast deprotonation of intermediate 2 by the amine to form intermediate 3, followed by slow departure of die fluorine ion. The other, is an uncatalyzed decomposition pathway (pafli b) that consists of the initial elimination of fluorine ion leading to aromatic ammonium salt 4, that is subsequently deproto-nated by the base present in die medium in a fast acid-base exchange (Scheme 33.4). 

The other major electrochemical modification approach has been that in which aromatic diazonium salts in an electrolyte solution are reduced at a diamond electrode this leads to the formation of an aryl radical, which can then attach to the diamond surface [74], This work is based on a series of papers in which the same technique was applied to the surface modification of glassy carbon and highly ordered pyrolytic graphite (HOPG) [75-78]. This approach may also be quite fruitful for tbe covalent modification of diamond surfaces, if the attachment is as robust as it is on glassy carbon surfaces. 

Perkin reaction A condensation between aromatic aldehydes and the sodium salts of fatty acids or their aromatic derivatives. The reaction between benzaldehyde and sodium ethanoate in the presence of ethanoic anhydride leads to sodium cinnamate... 

Reaction with arenediazonium salts Adding a phe nol to a solution of a diazonium salt formed from a primary aromatic amine leads to formation of an azo compound The reaction is carried out at a pH such that a significant portion of the phenol is pres ent as its phenoxide ion The diazonium ion acts as an electrophile toward the strongly activated ring of the phenoxide ion... 

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