Lithium alkylamides, reactions

When a deficit of the lithium alkylamide is used, dimeric chloride-bridged silylamides are obtained which are useful synthetic intermediates (Figure 27) they can also be prepared by redistribution reactions between LnCb and [Ln(N(SiMc3)2)3 some bromo- and iodo- analogues have been reported. 

Amidines 14 are cyclized to quinazolines 15 in lithium alkylamide or dialkylamide mediated reactions in which the construction of the quinazoline ring system and introduction of the amino substituent occur in the same reaction. Mechanistically, each fluorine of the trifluo-romethyl substituent of the amidine is displaced by a series of internal nucleophilic processes and the resulting quinazoline contains the amino function of the lithium reagent incorporated at the C4 position. The cyclization method is suitable for the synthesis of sterically congested quinazolin-4-amines and in syntheses of derivatives for which the corresponding chloroquinaz-olines are not readily available. ... 

This review article is concerned with chemical behavior of organo-lithium, -aluminum and -zinc compounds in initiation reactions of diolefins, polar vinyls and oxirane compounds. Discussions are given with respect to the following five topics 1) lithium alkylamide as initiator for polymerizations of isoprene and 1,4-divinylbenzene 2) initiation of N-carboxy-a-aminoacid anhydride(NCA) by a primary amino group 3) activated aluminum alkyl and zinc alkyl 4) initiation of stereospecific polymerization of methyloxirane and 5) comparison of stereospecific polymerization of methyloxirane with Ziegler-Natta polymerization. A comprehensive interpretation is proposed for chemistry of reactivity and/or stereospecificity of organometallic compounds in ionic polymerizations. 

Reactions with lithium alkylamides in hexamethylphosphoramide Elimination and substitution... 

The products from reaction of cyclohexene oxide (149) with a variety of lithium alkylamides have been investigated. Major pathways are considered relevant and these involve rearrangement to allylic alcohol or ketone or direct nucleophilic substitution. With lithium monoalkylamides the reaction product is essentially partitioned between cyclohex-2-enol (150) and amino-adduct... 

Analogous products were obtained from the reaction of silylene 85 with silyl lithium compounds, with alkali metal silylamides and alkali metal alkylamides, and sodium methoxide <2000CC1427, 2004JCD3288, 2005JCD2720, 2005CC5112>. In the case of the reaction with metallated silylamides a thermally initiated rearrangement (114 — 115) to give the new silylamide 115 took place (Scheme 11). 

Reaction with cyclic epoxides. The reaction of epoxides of medium-size rings with base (lithium di- -alkylamides) has been extensively studied by Cope and by Crandall (1, 610 611 2, 247). Two products are usually obtained an allylic alcohol formed by -elimination and a bicyclic alcohol derived from a carbene intermediate formed by a-elimination. Boeckman has now found that the ciirbcnc pathway is highly favored if n-butyllithium (3 equiv.) is used as base and if (he reaction is conducted at low temperatures, —78 to 25° in the case of cis-eyelooctene oxide (1) and m-cyclodecene oxide. The oxide of cyclododecene,... 

It should also be noted that copper-catalyzed Ullmann-type coupling of aryl halides with amines yields substituted products [206], and reaction with diphenylamine has been used to form triaryl-amines [207], Triarylamines may also be formed in a variation of the Meyers reaction [47] by displacement by lithium amides of fluoro- or methoxy-substituents activated by an ort/io-ester function [208], The oxidation of a-adducts is discussed in Chapter 11, but it should also be mentioned that aminated products may also be produced by the oxidation of adducts formed by the addition of amide or alkylamide ions at ring carbon atoms carrying hydrogen [209]. 

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