Lithium ethoxide in condensation

Lithium aluminum hydride, in reduction of 3-ethoxy-2-cyclohexenone to 2-cyclohexenone, 40, 14 Lithium ethoxide in condensation of benzaldehyde with tripbenylcin-namylphosphonium chloride to form 1,4-diphenyl-l, 3-butadiene,... 

Lithium ethoxide in condensation of benzaldehyde with triphenyldn-namylphosphonium chloride to form l,4-diphenyl-l,3-butadiene, 36 Lithium in formation of triphenylene from o-bromoiodobenzene, 106... 

Diphenyl telluropyran-4-one (typicalprocedure)7° 120 mL (0.12 mol) of a 1.0 M solution of lithium triethylborohydride in tetrahydrofuran are added to 7.65 g (60 mmol) of powdered tellurium under nitrogen, and the mixture stirred at 20°C for 4 h. A solution of sodium ethoxide (prepared from 5.52 g (0.24 mol) of sodium and 240 mL of absolute alcohol) is added to the dilithium telluride, 13.8 g (60 mmol) of bis(phenylethynyl) ketone are dissolved in a mixture of 150 mL of tetrahydrofuran and 150 mL of 1 M sodium ethoxide in ethanol this solution is poured as quickly as possible into the deep-purple-coloured dilithium telluride soluhon. The flask containing the reaction mixture is immediately placed in a water bath at 50°C and the temperature slowly increased over 30 min until ethanol begins to condense on the side of the flask. The water bath is removed and the mixture is stirred overnight at 20°C. Dichloromethane (400 mL) is then added, the resultant mixture is washed with 800 mL of water, and the organic phase is separated and concentrated to an oil. The oil is dissolved in 600 mL of dichloromethane, and the solution is filtered through a pad of sand. The filtrate is washed with 200 mL of 2% aqueous sodium chloride soluhon, dried with anhydrous sodium sulphate, filtered and evaporated. The brownish solid residue is triturated with 20 mL of butanenitrile and the fine yellow solid is collected by filtration yield 10.9 g (51%) m.p. 126-129°C (from acetonitrile). 

Lithium ethoxide appears to be the base of choice in condensations using bis-ylides, as shown in the formation of the metacyclophanediene (86). The trans,trans-... 

The reactivity of 2-alkyloxazoles in base-catalyzed additions and condensations is due to the intermediacy of delocalized anions analogous to (142). 2-Methyl-4,5-diphenyloxazole forms the adduct (278) by the action of benzophenone in liquid ammonia containing lithium amide (equation 89), and 2-methylbenzoxazole condenses with diethyl oxalate in the presence of potassium ethoxide to yield the keto ester (279). Anions with more extended conjugation are involved in the condensation of 2-(propen-l-yl)benzoxazole with diethyl oxalate (equation 90) and in the formation of the stilbene derivative (280) from 5-phenyl-2-p-tolyloxazole and benzylideneaniline (78AHC(23)l7l). 

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