Arsine oxides optically active—

Mori, K., and Toda, F. (1990) Optical Resolution of Arsine Oxides by Complexation with Optically Active [1,1 -Binaphthyl]-2,2 -diol, Bull. Chem. Soc. Jpn., 63, 2127-2128. 

Benzyl- or cinnamyl-triphenylarsonium bromides, upon reaction with aqueous sodium hydroxide at 100 °C, decompose into triphenylarsine oxide and toluene or 2-methyl-styrene, respectively . Since tertiary arsine oxides spontaneously racemize in water , alkaline hydrolysis of arsonium salts of this type cannot be used for the preparation of optically active arsines. 

The highly functionalized arsine 89 was resolved by the fractional crystallization of the diastereomers (/ ,/ as)-( + )- and (R,Sas)-(—)-92a . Oxidation of the dia-stereomer with BaMn04 produced the corresponding aldehyde complex that was converted into a complex of an optically active trans-As2N2 macrocycle (see below). 

Under anhydrous conditions, however, optically active tertiary arsine oxides can be prepared from optically active tertiary arsines and dinitrogen tetraoxide. Thus, (-f- )-(p-carboxyphenyl)ethylphenylarsine [(-l-)-36] reacts with N2O4 in nitromethane to give a solution of (-I-)-(p-carboxyphenyl)ethylphenyIarsine oxide [(-l-)-147], which lost its optical activity over 1.5 h. The optically active arsine oxides 145,146,153 were similarly generated in solution (Table 8), but only racemates or racemic hydrochlorides were isolated . The oxides can also be prepared from the corresponding arsine sulphides... 

TABLE 8. Optically active tertiary arsine oxides and sulphides... 

Despite the uncertain beginning, a variety of optically active tertiary arsines is now available for application in inorganic and organic synthesis. Tertiary arsines are powerful ligands for metals in a range of oxidation states, a feature that makes them particularly suitable for the design of complexes for stereochemical investigations and for use in... 

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