Configurational stability, at arsenic

Although the pyramidal inversion barrier for As in the arsanthracene system has not yet been reported, the AG for pyramidal inversion for a related sulfur derivative, 9,9-dimethyl-10-phenylthioxanthylium perchlorate, was calculated to be 25.4 kcal/mole at 200 5° (5). Since considerable evidence demonstrating ring flexibility in 9,10-dihydro-anthracene derivatives has accumulated, the isolation of optically active arsanthracene derivatives most probably is due to configurational stability of arsenic. 

Treatment of 2-chloro-1,3,2-dioxarsinanes (195) with alcohols and phenols in diethyl ether in the presence of excess of triethylamine yields the corresponding alkoxy and phenoxy derivatives (209 R = alkyl, aryl) <76CB493,76ZN(B)190>. Aksnes et al. reported the preparation of several 2-methoxy-and 2-phenoxy-substituted 1,3,2-dioxarsinanes in this way (Scheme 37) <75ACS(A)376,76ACS(A)327>. As a result of the configurational stability at the arsenic atom, nonequiUbrium mixtures of two... 

Equilibrium concentrations of semi-stabilized benzylidene ylides derived from optically pure arsonium salts and alkali metal ethoxides react with aromatic aldehydes to produce high yields of enantiomerically enriched tra s-2,3-diaryloxiranes and optically pure tertiary arsines with retention of configuration at arsenic (equation S)" -" . 

---