Carbon-arsenic double bonds

Oxidation of alcohol, carbonyl and acid functions, hydroxylation of aliphatic carbon atoms, hydroxylation of alicyclic carbon atoms, oxidation of aromatic carbon atoms, oxidation of carbon-carbon double bonds, oxidation of nitrogen-containing functional groups, oxidation of silicon, phosphorus, arsenic and sulfur, oxidative N-dealkylation, oxidative O- and S-dealkylation, oxidative deamination, other oxidative reactions... 

The Wittig reaction is a valuable addition to our synthetic arsenal because it forms carbon-carbon double bonds. In contrast with eliminations (Sections 11-6 and 11-7), it gives rise to alkenes in which the position of the newly formed double bond is unambiguous. Compare, for example, two syntheses of 2-ethyl-1-butene, one by the Wittig reaction, the other by elimination. 

Recently an arsenic amide derivative has reacted with an isocyanate, adding across the carbon—nitrogen double bond. I think this is the first example of a group V element which seems to be undergoing an insertion reaction. 

Typical oxidising dopants used include iodine, arsenic pentachloride, iron(III) chloride and NOPF6. A typical reductive dopant is sodium naphthalide. The main criteria is its ability to oxidise or reduce the polymer without lowering its stability or whether or not they are capable of initiating side reactions that inhibit the polymers ability to conduct electricity. An example of the latter is the doping of a conjugated polymer with bromine. Bromine it too powerful an oxidant and adds across the double bonds to form sp3 carbons. The same reaction may occur with NOPF, but at a lower rate. 

Tributylarsanc reacts with perfluorocyclobutene in diethyl ether at room temperature to form the corresponding ylide 3 in quantitative yield. Presumably, tributylarsanc attacks the double bond in the cyclobutene followed by fluoride ion elimination. Subsequently, fluoride ion adds to the intermediate at the olefinic carbon (I to the arsenic atom. Bromination proceeds much faster than iodination. 

These X-rays studies show that the interaction is greater in the case of antimony than in the case of arsenic. Despite the greater size of antimony than arsenic, the Sb — O distance is shorter than the As—O distance. In addition the Sb—C (ylidic) and As—C(ylidic) bond distances indicate that the Sb—C bond has more double-bond character than the As—C bond. In all cases these ylides take up Z,Z-conformations, both in solution (as observed by NMR spectra) and in the solid state, but in the solid state they are not symmetric, only one of the substituent groups being involved in the intramolecular interaction. This can be represented as in 40 and 41. In accord with such structures one of the bonds linking substituents to the ylidic carbon atom is shorter than the other. 

The addition of a carbon atom to the 0=N double bond has been reported using sulfur (equation 35)133 and arsenic ylides, halogen-stabilized carbenes, and diazo compounds.i i-i The best substrates are imines in which the nitrogen is substituted with an aromatic ring, substituted oximes, and hydrazones. 

Attempts to prepare arsolyl anions by reductive cleavage of s-chloro-2,3,4,5-tetramethylarsole or reductive cleavage of the permethylated l,l -biarsole result in erratic yields of the anion (153) and are contaminated by elemental arsenic. A superior procedure calls for reduction of the. 45-phenyl derivative (Scheme 35). With this procedure, analytically pure anion (153) is prepared in near quantitative yield by extracting the byproduct PhLi with ether after the reaction has finished. Reaction of this anion with 2.0 equivalents of TMEDA allows the preparation of crystals of its TMEDA adduct (68) that are suitable for x-ray analysis. This shows the nearly planar arsole ring to be rj-5 coordinated, the arsenic-carbon bonds to be intermediate between single and double bond... 

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