Alcohols lithium naphthalenide

Oxiranes and aziridines are reduced to alcohols and amines, respectively, for example by Ni/H2, Zn-NH4C1, P-I, Al-Hg, Na/NH3, Li/EtNH2 (7UOC330). Cleavage of aziridines with lithium naphthalenide provides synthetically useful dianions as shown in Scheme 29 (93TL1649,94JOC3210). 

Epoxy ketones are selectively reduced with lithium naphthalenide or Cp2TiCl in THF/MeOH ° to the (3-hydroxyketone. Other reduction methods can lead to the epoxy alcohol (see p. ). Reduction of epoxy amides with Sml2 in methanol gave the ot-hydroxyamide. ° ... 

From the experimental point of view, reductive desulfonylations with alkali metal arene radical anion complexes require a large excess of the radical anion, very short reaction times at low temperatures, and must be run under an inert atmosphere. Sodium or lithium naphthalenides in tetrahydrofuran at —78° or lower temperatures are typical reaction conditions. Tetrahydrofuran solutions of lithium naphthalenide are dark green. This color is lost when the substrate is added and restored once the reaction is finished. Upon completion, the excess reagent is quenched with a saturated aqueous solution of ammonium chloride or low molecular alcohols such as methanol or ethanol. 

Dianion Generation. Lithium naphthalenide efficiently de-protonates alkynyloxy " and carboxylate anions (eq 5). In addition, the previously mentioned phenomenon of reductive metalation has been exploited to access dianions fromhalohydrins, -halo carboxylic acids, and -halo carboxamides, and even trianions from -dihalo alcohols. A major pathway for the polyanionic species is -elimination (eq 6) when such processes can be avoided, the polyanions react according to Hauser s rule (eq... 

Thus, the treatment of t-butyl 4-bromobutyrate with such activated copper(O) at —78 °C leads to the corresponding copper derivate 1 that readily reacts with epoxides furnishing the corresponding alcohol 2 in 87% yield. Remarkably, the reactive copper(O) obtained by the reaction of CuCN 2LiCl [7] with lithium naphthalenide at low temperature is ideally suited for the preparation of functionalized allylic copper reagents such as 3 (Scheme 9.2). 

Its reaction with benzaldehyde provides the desired homoallylic alcohol 4 in 96% yield [8]. An improved procedure allowing the generation of an exceptionally active copper(O) reagent is obtained by the low-temperature reduction of lithium 2-thienylcyanocuprate 5 with lithium naphthalenide [9]. In this case, 1,4-additions to enones in the presence of MejSiCl [10] proceed especially well. 

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