REDUCTIVE OPENING OF 2-PHENYL-1,3-DIOXOLANES BY A NAPHTHALENE-CATALYZED LITHIATION - SYNTHETIC APPLICATIONS

The reaction of 2-phenyl-1,3-dioxolanes 1a,b with an excess of lithium powder in the presence of a catalytic amount of naphthalene (4 mol %) in tetrahydrofuran at -40-degrees-C followed by successive reaction with an electrophile and final hydrolysis with water at the same temperature yields the corresponding monoprotected 1,2-diols 2aa-2bf. The same process but allowing to rise the temperature to 20-degrees-C before the hydrolysis affords alcohols 3aa-3bd. The use of 2,2-diphenyl-1,3-dioxolane 1d, under similar reaction conditions as for compounds 2, permits the isolation of 2,2-diphenylalcohols 11da-11dc, resulting from the reaction with two different electrophiles. A mechanistic rationalization for all processes is given.