The reduction of alkylnaphthalenes with lithium in liquid ammonia

Abstract

AbstractThe reduction of naphthalene and alkylnaphthalenes with lithium in liquid ammonia has been studied. With excess of alkali metal and in the absence of a proton donor the reaction yields tetralins. The reduction of 1, 4‐dideuteronaphthalene shows that the first proton addition at an α‐position is irreversible and that the amide‐catalyzed isomerization of the initially formed 1, 4‐ into the 1, 2‐dihydronaphthalene is mainly a one step process. This isomerization is the rate‐determining step in the reduction to tetralin. Reduction of 1‐alkyl‐ and 1, 4‐dialkyl‐naphthalenes occurs mainly in the unsubstituted ring. With 2‐alkyl‐naphthalenes the selectivity of ring reduction depends on the alkyl group; in 2‐methylnaphthalene the substituted ring is about twice as reactive as the unsubstituted ring whereas the reverse is true for 2‐t‐butylnaphthalene.