Lithium reactions with vinyl

Other useful nucleophiles for the ring opening of aziridines include bromide, as shown in the Amberlyst-15 catalyzed reaction of lithium bromide with vinyl aziridine 167 <02TL5867> and hydride, which can be delivered by lithium triethylborohydride. This is illustrated by the conversion of tosyl azabicyclo[3.1.0]hexene 169 to the corresponding protected cyclopentenyl amine (170) in 79% yield <02TL723>. 

In the following, the realization of this concept will be briefly described. The synthesis of the tetronomycin building block 55 (Scheme 5) starts from the chiral aldehyde 51, which is easily accessed from D-arabinose. Reaction with vinyl-lithium leads to a 1 1 mixture of the epimeric alcohols 52a and 52b, which are separated by HPLC. Interestingly, both diastereomers can be converted (on separate routes) into the building block 55. Both the Pd-eatalyzed key steps (53 54 and 56 57) proceed with high diastereo-selectivity. 

A novel method for preparing amino heterocycles is illustrated by the preparation of 2-amino-5-methylthiophene (159). In this approach vinyl azides act as NH2 equivalents in reaction with aromatic or heteroaromatic lithium derivatives (82TL699). A further variant for the preparation of amino heterocycles is by azide reduction the latter compounds are obtained by reaction of lithio derivatives with p- toluenesulfonyl azide and decomposition of the resulting lithium salt with tetrasodium pyrophosphate (Scheme 66) (82JOC3177). 

This procedure illustrates a general method for the preparation of alkenes from the pal 1 adium(Q)-cata1yzed reaction of vinyl halides with organo-lithium compounds, which can be prepared by various methods, including direct regioselective lithiation of hydrocarbons. The method is simple and has been used to prepare a variety of alkenes stereoselectively. Similar stoichiometric organocopper reactions sometimes proceed in a nonstereoselective... 

Vinylic copper reagents react with CICN to give vinyl cyanides, though BrCN and ICN give the vinylic halide instead." Vinylic cyanides have also been prepared by the reaction between vinylic lithium compounds and phenyl cyanate PhOCN." Alkyl cyanides (RCN) have been prepared, in varying yields, by treatment of sodium trialkylcyanoborates with NaCN and lead tetraacetate." Vinyl bromides reacted with KCN, in the presence of a nickel complex and zinc metal to give the vinyl nitrile. Vinyl triflates react with LiCN, in the presence of a palladium catalyst, to give the vinyl nitrile." ... 

In the case of symmetrical divinyl tellurides, the displacement of both vinyl groups is achieved by employing 2 equiv of n-butyllithium. Aryl vinyl tellurides give a mixture of products, since both Ar-Te and vinyl-Te bonds are transmetallated on reaction with n-BuLi, leading to vinyl- and aryllithiums. The butyl vinyl tellurides give only the desired vinyl-lithiums. The reactions are stereospecific with retention of the C=C bond geometry. °... 

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