A similar solution of dianion was prepared from 1.7 g (6.9 mmol) of la in 15 ml of dry THF and treated dropwise with 1.05 g (10 mmol) of benzaldehyde. After stirring for another 15 min the mixture was quenched with water and the product was isolated. The resulting viscous oil was purified by chromatography on silica gel, eluting with carbon tetrachloride- chloroform. This yielded 2.07 g (85%) of clear oil which crystallized on standing: mp 115- ...