Allylindium derivatives

Reactions of allylindium derived from allylic dihalo compounds 681... 

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). 

For example, the Z form of methyl 2-(bromomethyl)-2-butenoate has been demonstrated to possess greater thermodynamic stability than the E isomer (Scheme 3) (27). Should this ordering carry over to the allylindium derivative and a high Felkin-Anh transition-state preference be exercised, the 3A-syn 4,5-anti product should be dominant. The illustrated examples reveal that this is so. Only a modest diminution in coupling diastereoselectivity is observed as the relative size of the aldehyde substituent is increased from methyl to the phenyl and cyclohexyl levels (20). 

A new preparative method for allylic indium(m) reagents via a reductive transmetallation of 7r-allylpalladium(n) or 7T-allylnickel(n) complexes with indium(i) salts is reported. This method enables the use of a wide variety of allylic compounds, such as allylic chlorides, acetates, and even allylic alcohols, in combination with Pd or Ni catalysts.43-50 7r-Allylpalladium(ii) resulting from the addition of arylpalladium(n) to allene is also transformed by metallic indium to the corresponding allylindium.51-54 Similarly, propargylindium(m) can be prepared from the corresponding propargyl alcohol derivatives.55-58... 

Pentadienylindium, a vinylog of allylindium, reacts with carbonyl compounds regioselectively at the 7-position to give 1,4-pentadiene derivatives (Scheme 7).107-109 n the presence of InCl3, pentadienylstannane similarly reacts with a-alkoxyaldehydes to produce the corresponding 7-adducts (Scheme 8).110... 

The reactions involving sulfur derivatives are minimally diastereoselective, indicating that the allylindium reagent is not thiophilic (Table 3).159 The modest levels of diastereoselectivity observed in all the sulfur examples, which are... 

Pan et al. reported similar reactions of / -quinones to 4-allyl-4-hydroxycyclohexa-2,5-dienone derivatives (Equation (26)).194 Unsymmetrical quinones show high selectivity in the addition of allylindium reagents to the carbonyl group. Indium-mediated allylation of 1,2-diones occurs via a y-coupling fashion to yield ct-hydroxy keto compounds. In some cases of cinnamylation, the corresponding a-coupling products are obtained (Equation (27)).195,196... 

Allylindium reacts with activated O-functionalyzed oximes as exemplified by a variety of glyoxylate derivatives (Scheme 66). This method gives the corresponding free (or protected) amines in a one-pot process. The reaction is regiospecific and can be carried out under remarkably mild conditions so that even oxime ethers are subjected to the typical reaction conditions.267... 

Indium-mediated allylation of a nitro group is achieved in aqueous media to give A,A-diallylamine and 7V,0-diallylhydroxylamine (Equation (81)) 316 In situ generated sulfonium salts derived from a,/3-enones undergo a nucleophilic substitution with allylindium reagents to give the corresponding Michael addition products (Scheme 83).317... 

While y-selectivity is usually 4-chloro-2-butenyl benzyl ether the derived allylindium reagent a An intramolecular reaction ih... 

While y-selectivity is usually observed in reaction with substituted allyl halides (e.g., 4-chloro-2-butenyl benzyl ether"), 3-bromo-3,3-difluoro-l-propene behaves differently as the derived allylindium reagent adds to aldehydes like a,ot-difluoroallyl carbanion. ... 

The enantioselective asymmetric allylation of imines has been a synthetic challenge, the initial solutions of which required stoichiometric amounts of chiral allylbor on [87], allylsilane [88], allylzinc [89], or allylindium reagents [90]. Itsuno showed that a chiral B allyloxazaborolidine derived from norephedrine could add to the N trimethylsilyl imine prepared from benzaldehyde in high yield and enantiomeric excess (Scheme 1.22) [91]. Brown later reported that B allyldiisopinocamphenylbor ane is also very effective for the allylation of the same electrophiles, but the addition of a molar amount of water is necessary to obtain high yields [92]. The diastereo and... 

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... 

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. ... 

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). 

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