Pentachlorophenyl derivatives

The related pentachlorophenyl derivative, [Tl(4,4 -bipy) Au(C6Cl5)2 ] 70, was obtained as an orange solid, either by reacting the polymeric precursor 31 with an equimolecular amount of 4,4 -bipyridine or from complex 67 and half an equivalent of the aromatic amine [68]. Its solid-state structure is completely different from that of... 

Similarly to the results observed in the previous case, the structural differences affected the optical properties of the complexes. While in the former a single emission was observed in the solid state, both at room temperature (440, exc. 390 nm) and at 77 (460, exc. 360 nm) the latter showed one band (510, exc. 450 nm) and one shoulder (560 nm) at room temperature, and two independent emissions (510, exc. 370 nm 550, exc. 480 nm) at 77 K. This pentachlorophenyl derivative was also luminescent in solution, displaying a band at 530 nm (exc. 345 nm), which was not present in the precursor complexes or in the pentafluorophenyl derivative. Therefore, in this case, as in the previous one, it is proposed that the TI H interaction in the solid state remained in solution and was responsible for the luminescence behavior observed in this state. 

C6C15) with dimethylsulfoxide (DMSO), which leads to the synthesis of [Tl2 Au(C6F5)2 2 p-DMSO 3] or [Tl2 Au(C6Cl5)2 2 h-DMSO 2]ra, respectively.62 The crystal structure of the complex with fluorine shows a monodimensional polymer formed by repetition of [Au--Tl(p-0 = SMe2)3Tl] units, with gold-thallium interactions of 3.2225(6)-3.5182(8), while the pentachlorophenyl derivative contains two bridging DMSO molecules and an additional [Au(C6Cl5)2] anion. In addition, a thallium-thallium interaction of 3.7562(6) A appears in the latter (Fig. 21). 

Arylgold(I) compounds can be similarly prepared to alkyl derivatives via the organolithium or the Gridnard route. These methods have been used to prepare pentachlorophenyl,1641 4,4 -octa-fluorobiphenyl (Equation (27)),2109 2,4,6-tris(trifluoromethyl)phenyl,1 2,21 0 triphenylar-... 

Varela et al. have described some stereoregular hydroxylated polymannaramides (91) [93] by reaction of o-mannaro-l,4 6,3-dilactone (90) with even-numbered alkylenediamines (n = 2, 6, 8, 10, 12). Hydroxylated stereoregular and nonstereoregular polyamides were also prepared by the same authors [94] from hexam-ethylene diamine and pentachlorophenyl (25)-5-oxo-2-tetrahydrofurancarboxylate 93, the latter being derived [95] from the chiral (25)-2-hydroxypentanedioic acid 5,2-lactone (92), a compound obtained [96] by deamination of the easily available L-glutamic acid. 

Pentachlorophenol and its salt, sodium pentachlorophenate, are used primarily as wood preservatives on telephone poles, pilings and fence posts. In Europe, pentachlorophenol and its derivatives, sodium pentachlorophenate and pentachlorophenyl laurate are used to control sap stain in green lumber. It is also used in Europe on millwork to prevent the growth of mould and fungi, and as a preservative for waterproof materials (i.e., tarpaulins) that are used in outdoor applications. In the United States, it is used almost entirely for treatment of utility poles (Agency for Toxic Substances and Disease Registry, 1994). 

As mentioned above, thiazolidine-4-carboxylic acid is characterized by an anomalously low basicity and thus difficult acylation in peptide synthesis. 189 Therefore, the incorporation of this amino acid residue into a growing peptide chain is preferentially preformed via dipeptide derivatives. 139 Suitably N-protected amino acids are coupled directly to the thiazolidine-4-carboxylic acid by the acid fluoride 139 or iV-carboxyan hydride 1392111 methods. The resulting dipeptides are used as building blocks without risk of racemization 139 and standard coupling procedures are applied as pentachlorophenyl esters prepared by the mixed anhydride procedure 121 or PyBOP. 171 ... 

Dvortsak et al.117 found that bis(pentachlorophenyl)malonates and 2-aminopyridine formed the pyrido[l,2-a]pyrimidines (63 R = H) even at room temperature in acetone in the presence of triethylamine. By the reaction of bis(2,4,6-trichlorophenyl)malonates with 2-(monosubstituted amino)pyridines at 160-175rC, the 1-substituted derivatives of the pyrido[l,2-a]pyrimidines (63) were prepared.114-116... 

In both structures the gold atoms are linearly coordinated to two pentachlorophenyl rings with similar Au-C distances and C-Au-C angles (see Table XVIII). A remarkable difference is observed in Au- -Tl distances, which range from 3.0331(6) to 3.1887(6) A in the butterfly-type compound while the dioxane derivative displays the shortest Au- -Tl distance described to date (2.8935(3) A),149 151-157 being even shorter than the sum of Au and Tl covalent radii (3.08158 or 2.92 A159). The first complex also presents an intramolecular Tl- -Tl interaction of 3.6027(6) A, similar to the distances observed in dimeric [Tl(S2CNEt)2]2 (3.60 and 3.62 A).160... 

Further derivatives which have been prepared are tetrakis(dimethylphenyl-silyl)silane217 and pentachlorophenyl-tris(trimethylsilyl)silane213. The chlorination of a methyl group by treatment with CH3COCI/AICI3507 gives Si(Sime2CH2Cl)4. 

Phenolic esters are obtained similarly. The presence of a nitro group in the aromatic nucleus and the use of pyridine as solvent facilitates the reaction. This reaction is recommended for the characterization of phenols. 2,4,5-Trichlorophenyl-, pentachlorophenyl-, 4-nitrophenyl- and thiophenyl esters of N-acylamino acids are prepared in this manner. These aromatic esters are used in the stepwise lengthening of peptides, du Vigneaud and coworkers synthesized lysine vasopressin from a nonapeptide which they prepared stepwise using the nitrophenyl ester method. Room temperature esterification of dicarboxylic acids and diphenols are also carbodiimide mediated using the 1 1 complex derived from DMAP and p-toluenesulfonic acid as catalyst Methacrylic acid is also esterified with phenols using carbodiimides and DMPA to mediate the reaction. ... 

It has been concluded from pKa measurements and fluorine NMR data on pentafluoro-biphenyl derivatives, for example C6F5C6H4CO2H, C6F5C6H4F etc., that the penta-fluorophenyl group inductively withdraws electrons more strongly than phenyl but much less strongly than trifluoromethyl, whilst pentafluorophenyl and pentachlorophenyl have a similar capacity for electron withdrawal [40],... 

Bis-(trifluoromethyl)-phenyl plays the role of migrating ring in the Smiles rearrangement in the Najera and co-workers [106,107] modification of the olefination reaction. Judka and Makosza (Judka and Makosza, 2006, personal commimication) have shown that pentachlorophenyl and some very simple phenyl derivatives may be conveniently used in the olefination reactions imder mild conditions. Indubitably, several other aromatic and hete-rocycHc systems will be estabhshed as the templates in the direct olefination reaction, allowing for convenient choice of experimental conditions and stereochemical bias. 

Aminopyridine is reported to react vigorously with chlorosulfonyl isocyanate at 0°C producing an urea intermediate (12) which in the presence of diisopropylethylamine was shown to yield pyrido[l,2-i][l,2,4,6]thiatriazine-5(6/0 OIte-l l-dioxide (2) (Scheme 3) <79H(6)815>. Its V-benzyl derivative (3) was selectively prepared by the reaction of 2-benzylaminopyridine (13) with either chlorosulfonyl isocyanate via intermediate (15) or pentachlorophenyl chlorosulfonyl carbamate (PCPCSC) in the presence of diisopropylethylamine via intermediate (14) (Scheme 4) <86H(8)2255>. The reaction of 2-alkyl-2-chlorosulfonyl carbamoyl chlorides with 2-aminopyridine resulted in 2-alkylpyrido [l,2-i ][ 1,2,4,6]thiatriazine-3(2/0-one-1,1-dioxides (5) (Equation (2)) <77CR(S)238>. 

Synthesis of sequential peptides usually relies on an activated derivative of the repeating unit from which the amine-protecting group is removed by acid-olysis. Pentachlorophenyl esters were found to produce high molecular weight materials. The reaction is started by deprotonation with a tertiary amine but the addition of a small amount of a secondary amine as initiator is also advisable ... 

In some reactions involving Li and Me3SiCl, as with pentachlorophenyl-trimethylsilane, the yield of the allene is in excess of 50% on the basis of two allene molecules deriving from one polysubstituted benzene. However, the allene is also formed from a cycle with only five carhon atoms such as pentachloropyridine. Furthermore, the yield of allene from a simple linear compound such as hexachloropropene is in excess of 75%. 

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