Aryl compounds

4 Aryl compounds. diuil d terhim-induced li-NMR isotope shifts have been determined for C5H5LL On the basis of the isotopic fingoprints observed in the li-NMR spectra of C 5- Ij/C6D5- Li mixtures, the aggr ation of phenyUithiums can be establidied in a 

Rearrangement of o-BiCgH4CH2CH2CH2li to o-LiC H4CH2CH2CH2Br occurs via an inter-molecular mechanism in contrast o-BrC(H4CH2 2 H2 2)iiBr proceeds via an intramolecular pathwi.  

Other MOCVD compounds are the aryls, which are formed from aromatic hydrocarbons, that is compounds that have six-member rings with three carbon double bonds, such as phenyl shown below  

Common metallo-organic alkyls, alicyclic, and aryl compounds and their relevant properties are listed in Table 4.1 l l Many additional organometallic compounds are available commercially as listed in Ref 7. 

Most metallo-organic compounds are monomers with some important exceptions, such as trimethyl aluminum which is a dimer. Their vapor pressures are usually directly related to the molecular weight, with the lower molecular weight compounds having the higher volatility. 

To be useful as CVD precursors, a metallo-organic compound should be stable at room temperature so that its storage and transfer are not a problem. It should also decompose readily at low temperature, i.e., below 500°C. The compounds listed in Table 4.1 meet these conditions with the exception of the alkyls of arsenic and phosphorus, which decompose at higher temperatures. For that reason, the hydrides of arsenic and phosphorus are often preferred as CVD precursors (see Ch. 3). These hydrides however are extremely toxic and environmental considerations may restrict their use. 

Alkyls, Alicyclic, and Aryl Metallo-Organic Componnds 

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It is a colourless gas which decomposes on heating above 420 K to give metallic tin, often deposited as a mirror, and hydrogen. It is a reducing agent and will reduce silver ions to silver and mercury(II) ions to mercury. SnSn bonding is unknown in hydrides but does exist in alkyl and aryl compounds, for example (CH3)3Sn-Sn(CH3)3. 

Dienes and allylarcncs can be prepared by the Pd-catalyzcd coupling of allylic compounds with hard carbon nucleophiles derived from alkenyl and aryl compounds of main group metals. Allylic compounds with various leaving groups can be used. Some of them are unreactive with soft nucleophiles, but... 

The aryl compounds are unstable substances which decompose on standing and are hydrolyzed ia moist air. The chlorides are readily prepared by the actioa of hydrochloric acid oa the corresponding arylstibonic acids. Tetraacetatopheaylantimoay [116122-86-27], C24H2yOgSb, has beea prepared (168) ... 

Cesium forms simple alkyl and aryl compounds that are similar to those of the other alkah metals (6). They are colorless, sohd, amorphous, nonvolatile, and insoluble, except by decomposition, in most solvents except diethylzinc. As a result of exceptional reactivity, cesium aryls should be effective in alkylations wherever other alkaline alkyls or Grignard reagents have failed (see Grignard reactions). Cesium reacts with hydrocarbons in which the activity of a C—H link is increased by attachment to the carbon atom of doubly linked or aromatic radicals. A brown, sohd addition product is formed when cesium reacts with ethylene, and a very reactive dark red powder, triphenylmethylcesium [76-83-5] (C H )2CCs, is formed by the reaction of cesium amalgam and a solution of triphenylmethyl chloride in anhydrous ether. 

Another source of C-unsubstituted derivatives are o-aminopyridine aldehydes e.g. 216 - 217) (60JCS1370), and the corresponding ketones may be used to furnish C-aryl compounds (71GEP2051013). 

Alkylisothiazolium salts (61) undergo N—S bond cleavage when treated with hydrogen sulfide or thiophenol to form acyclic products (62), but 2-aryl compounds give 1,2-dithioles (63 or 64 Scheme 9) (75SST(3)54l, 77SST(4)339). 

One other feature of the data in Table 10.10 is worthy of further comment Notice that alkyl substituted acylium ions exhibit a smaller ortho para ratio than the various arpyl systems. If steric factors were dominating the position selectivity, one would expect the opposite result A possible explanation for this feature of the data could be that the aryl compounds are reacting via free acylium ions, whereas the alkyl systems may involve more bulky acyl chloride-catalyst complexes. 

The results in the ionic liquid were compared with those obtained in four conventional organic solvents. Interestingly, the reaction in the ionic liquid proceeded with very high selectivity to give the a-arylated compound, whereas variable mixtures of the a- and (3-isomers were obtained in the organic solvents DMF, DMSO, toluene, and acetonitrile. Furthermore, no formation of palladium black was observed in the ionic liquid, while this was always the case with the organic solvents. 

Ruthenium and osmium form some remarkably stable alkyls and aryls compounds, often in unusually high oxidation states. 

Aryl compounds containing another donor atom in the orf/io-position like Ag(C6H4CH2NMe2) have also been isolated (they are probably clusters). 

MOCVD PRECURSORS ALKYL, ALICYCLIC, AND ARYL COMPOUNDS... 

In the presence of a precious metal catalyst, aryl halides can undergo dehalo-dimerization to give biaryl products, with varying degrees of selectivity. The major byproduct of this reaction is usually the dehalogenated aryl compound. This type of chemistry is currently one of the very few viable means for the large scale preparation of biaryl compounds. 

The course of the reaction of phosphinous amides with carboxylic acid chlorides is dependent on the characteristics of the iV-residue. Thus with N-aryl compounds this reaction gives chlorophosphanes and carboxamides. With AT-alkyl analogs the primary reaction products have not been identified but they hydrolyzed to carboxaldehydes [120]. 

AstraZeneca has filed a patent application on novel bis-aryl compounds as CB1/CB2 agonists that lack CNS penetration and thus avoid the unwanted side effects associated with activation of central CBi receptors [210]. Over 100 compounds are specifically claimed e.g. (321). Compounds were tested in receptor binding assays using human CBi and CB2 receptor preparations. Respective K values were in the ranges 50-5,000 and 15-2,800 nM, although no specific data were presented. 

In order to synthesize the DIOP-based ligands, the aldehyde derivatives 3 were treated with commercially available diethyl tartrate in the presence of catalytic amount of PPTS (Scheme 21.2). While good conversions were attained with the naphtyl derivative, they were low with all other aryl compounds and unsuccessful with heteroaromatic moieties (yields < 10%). 

E. Hydrolysis of Si-C Bonds 1. Alkyl, Alkenyl, and Aryl Compounds... 

For arylpolysilanes the results are quite different.(34) The 29Si NMR for (PhSiMe)n is shown in Figure 6 it consists of three broad lines with relative intensity 3 3 4, each line evidently containing a cluster of resonances. The patterns for other aryl-alkylpolysilanes differ, but in general two or three broad resonances are found none of the aryl compounds studied so far has given a symmetrical pattern like those observed for the alkylpolysilanes of Figure 5. 

Table 9.1 13C chemical shifts of some common heterocyclic and fused aryl compounds. 

Compounds containing the iV-thiosulfinylamino group (R—N=S=S) have been reported recently.85 "88 The aryl compounds are rather unstable purple oils which show promise as sulfur transfer agents, although few definitive examples have yet been reported.87... 

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