Sulfur phosphorus halides

The synthetic utility of many of the substitution reactions described so far is limited because there are well-established thermal routes to the same products. However, a third group of photochemical nucleophilic substitutions involves aryl halides and nucleophiles based on sulfur, phosphorus or, of particular importance, carbon. Two examples are the reaction of bromobenzene with the anion of t-butyl methyl ketone 13.12), and the replacement of bromine by cyanomethyl in 2-bromopyridine (3.13). This type of reaction offers a clear advantage over lengthy thermal alternatives, and intramolecular versions have been used in the synthesis of indoles (e.g. 3.14) or benzofurans from o-iodoaniline or o-iodoanisole respectively. 

Sulfur-phosphorus bidentate ligands such as o-C6H4(PPh2)SMe fail to form 2 1 complexes with palladium(II) halides, but o-CgH AsPh SMe forms [PdX2(L—L)2] (X = Cl, Br) from aqueous acetone. 5 The crystal structure of the diiodide complex has been determined and shows a pseudohexacoordinate palladium(II) centre with long trans axial Pd S interactions (3.84 A). 

Alcohols can also be converted to alkyl halides by phosphorus halides such as PCI PBr3, and PI via an 5 2 mechanism resulting in poor yields with tertiary alcohols. Another reagent for producing alkyl halides from alcohols is thionvl chloride, OCl2, resulting in sulfur dioxide and hydrochloric acid. 

X-ray Photoelectron Spectroscopy (XPS) tests were conducted on surfaces lubricated with a sulfur-containing extreme pressure additive, dibenzyl sulfide (Baldwin, 1976 Bird and Galvin, 1976). The films can arise from the use of additives that contain sulfur, phosphorus, chlorine, bromine, or boron and the differences in reactivity are affected by the formation of protective layers. Triboinduced electrons are said to activate the formation of iron halides, iron phosphates and iron sulfides (Dorison and Ludema, 1985 Grunberg, 1966 Kajdas, 2001 McFadden et al., 1998 ). When a chemical reaction takes place, e.g., oxygen interacts with aluminum to form aluminum oxide, a large oxygen peak is seen at approximately 500 eV in the Auger electron spectra (Benndorf et al., 1977 Nakayama et al., 1995). 

These and other methods of introducing halogen into heterocycles, such as the transformation of a- and y-hydroxypyridinoid bases with inorganic acid halides, the treatment of pyridinoid A-oxides with sulfur or phosphorus halides, and the decomposition of diazonium compounds, are treated adequately in existing references. 

Another time-honored reaction is the acylation-dehydration of thiosemicarbazides. The acylation is generally performed with an acid chloride, and elimination of water from the intermediate 1-acylthio-semicarbazide is conveniently elFected with cold concentrated sulfuric acid or with 100 % phosphoric acid. Phosphorus halides have... 

Four- and eight-membered heterocycles containing phos-phorus(in), nitrogen and sulfur(VI) have been obtained by reacting phosphorus halides with dialkylsulfamide 02S(NHR )2 (Scheme 59). ... 

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