Allylindium species

The literature in this area is fairly sparse, presumably because of the ease of preparation of allyl- and propargylamines by nucleophilic amination. The reaction of allylindium species with aryl azides to give A -allylarylamines was mentioned earlier (Eq. 25). It has also been applied to the indium species derived from methyl 2-(bromomethyl)acrylate.269 The amination of alkylzirconium species mentioned above (Eq. 41) can also be applied to allenes (Eq. 51).116... 

Formation of allylindium species for reaction with sulfinimines in water is benefited by a halide salt (of Na, Li, K, NH4), with regard to producing good yields of the adducts and diastereoselectivity. ... 

Allylindium species are cleaved to C-centered radicals therefore they are alternatives to allyltins for ring closure. UV irradiation is beneficial to the chemical step. ... 

The indium-mediated allylation reaction is an aldol-type reaction where the nucleophile is an allylindium species usually generated from allylic halide and indium. By far the greatest number of indium-mediated organic reactions involves the allylation of unsaturated compounds, and the list of indium-mediated allylations is formidable. In principle, there are five types of indium-mediated allylation reactions depending on the unsaturated functional groups (Scheme 9). 

Dibromopropene acts as a gem-allyl dianion synthon. However, the reaction is not as clean as one might desire, due to competing reductive debromination of the 1 1 products., l-Dichloro-2-propene undergoes a y-selective addition process, affording syn-chlorohydrins, but the allylindium species derived from 3-bromo-l-trimethylsilylpropene attacks aldehydes with the a-carbon. ... 

By every indicator we have uncovered, chelation to indium(III) is seen to operate in water where possible, with resultant control of reaction diastereoselectivity. Erosion of selectivity is sometimes encountered, but the causative factors are exu insic to the chelation phenomenon. In this connection, a comparative analysis of additions involving crotylindium and 3-bromoaIlylindium to 2-hydroxypropanal is particularly informative (Scheme 2) (/6). In the case where R is methyl, the proportion of the syn,syn and syn,anti isomers is maximized at 5.6 1, a value closely comparable to that for simple allyladon (syn/anti = 7.5 1). When R = Br, the maximum value is only 2 1. In fact, the latter process qualifies as a fully nonselective process. The prevailing hypothesis is that this behavior is linked to facile geometric isomerization in the allylindium species as noted for the Grignard (77), potassium 18), and lithium derivatives (79). 

Under these conditions, trivalent allylindium species analogous to Grignard reagents are generated in situ ... 

Homoallylic alcohols are provided by Pd-catalyzed reaction of iodobenzene, allene and aldehydes (Scheme 16.15) [19, 20]. A nucleophilic allylindium intermediate is generated through transmetallation of a Jt-allylpalladium species with indium. Such a Jt-allylpalladium complex can alternatively be provided through carbopalladation of ArPdl to a proximate acetylene followed by insertion of allene. 

A three-component reaction based on the umpolung of re-allylpalladium (II) complexes indium metal was reported by Grigg and co-workers (Scheme 8.31) [74]. In this reaction, the electrophilic nature of the n-allyl palladium species generated from aryl halides and allenes is reversed by transmetallation with indium metal. The resultant nucleophilic allylindium reagent subsequently adds to the third component - aldehyde [75] or imine [76] - to give the corresponding homo-allylic alcohol 64 or amine 65 respectively. 

Stannanes and silanes may act as carbanion derivatives that can be activated with suitable Lewis adds. Thus, as shown by Cossy et al. [440], allylstannanes may be transmetalated with InCU to generate allylindium derivatives in situ. The latter can react with aldehydes to give mixtures of syn and anti adducts (with aromatic aldehydes and 2-buten-l-al). With aliphatic aldehydes, only the anti adducts are observed. The authors concluded that product mixtures were partly caused by the kinetic formation of a mixture of indium (Z)- and ( )-allyl esters prior to the condensation. They then allowed the indium species to equilibrate prior to the aldehyde addition and obtained mainly anti adducts (627, 628) (Scheme 130). 

Allyl-2-azetidinones are synthesized by displacement of the corresponding acetoxy derivatives, A preparation of homoallylic amines can take advantage of the reactivity of allylindium reagents on iminium species that are formed in situ. ... 

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