Indium-mediated allylation

In 1991, Li and Chan reported the use of indium to mediate Barbier-Grignard-type reactions in water (Eq. 8.49).108 When the allylation was mediated by indium in water, the reaction went smoothly at room temperature without any promoter, whereas the use of zinc and tin usually requires acid catalysis, heat, or sonication. The mildness of the reaction conditions makes it possible to use the indium method to allylate a methyl ketone in the presence of an acid-sensitive acetal functional group (Eq. 8.50). Furthermore, the coupling of ethyl 2-(bromomethyl)acrylate with carbonyl compounds proceeds equally well under the same reaction conditions, giving ready access to various hydroxyl acids including, for example, sialic acids. 

Whitesides et al. examined the effect of substituents on the allyllic moiety of the indium-mediated reactions in water and found that the use of indium at room temperature gave results comparable to those of tin-mediated reactions carried out at reflux.110 Replacement of the aqueous phase with 0.1 N HC1 further increased the rate of the reaction. The transformation can also be carried out with preformed allylindium chloride. 

The indium-mediated allylation carried out with allylstannanes in combination with indium chloride in aqueous medium was reported by Marshall et al.113 Allylindium was proposed as the reaction intermediate. Various aldehydes can be alkylated very efficiently with 3-bromo-2-chloro-l-propene mediated by indium in water at room temperature. Subsequent treatment of the compound with ozone in methanol followed by workup with sodium sulfite provided the desired hydroxyl ester in high yield.114... 

Indium-mediated allylation of an unreactive halide with an aldehyde132 was used to synthesize an advanced intermediate in the synthesis of antillatoxin,133 a marine cyanobacteria (Lyngbya majus-cula) that is one of the most ichthyotoxic compounds isolated from a marine plant to date. In the presence of a lanthanide triflate, the indium-mediated allylation of Z-2-bromocrotyl chloride and aldehyde in saturated NH4C1 under sonication yielded the desired advanced intermediate as a 1 1 mixture of diastereomers in 70% yield. Loh et al.134 then changed the halide compound to methyl (Z)-2-(bromomethyl)-2-butenoate and coupled it with aldehyde under the same conditions to yield the desired homoallylic alcohol in 80% yield with a high 93 7 syn anti selectivity (Eq. 8.55). 

The indium-mediated allylation of trifluoroacetaldehyde hydrate (R = H) or trifluoroacetaldehyde ethyl hemiacetal (R = Et) with an allyl bromide in water yielded a-trifluoromethylated alcohols (Eq. 8.56).135 Lanthanide triflate-promoted indium-mediated allylation of aminoaldehyde in aqueous media generated (i-airiinoalcohols stereoselectively.136 Indium-mediated intramolecular carbocyclization in aqueous media generated fused a-methylene-y-butyrolactones (Eq. 8.57).137 Forsythe and co-workers applied the indium-mediated allylation in the synthesis of an advanced intermediate for azaspiracids (Eq. 8.58).138 Other potentially reactive functionalities such as azide, enone, and ketone did not compete with aldehyde for the reaction with the in situ-generated organo-indium intermediate. 

Allylation of the C-3 position of the cephem nucleus was accomplished by either indium-mediated or indium trichloride-promoted tin-mediated allylation reactions in aqueous media. Both methods gave 3-allyl-3-hydroxycephams in moderate to excellent yields.149... 

A new method has been developed for the synthesis of ( )-3-methyl Baylis-Hillman-type adducts with high E/Z (>93%) selectivity in modest to good yields. The process consists of two steps an indium-mediated allylation reaction and a simple base-catalyzed isomerization step (Eq. 8.61). Various aldehydes were allylated with allyl bromides using indium under very mild conditions in aqueous media and thus converted to the Baylis-Hillman-type adducts.150... 

C-branched sugars or C-oligosaccharides are obtainable through indium-promoted Barbier-type allylations in aqueous media.151 Indium-mediated allylation of a-chlorocarbonyl compounds with various allyl bromides in aqueous media gave the corresponding homoallylic chlorohydrins, which could be transformed into the corresponding epoxides in the presence of a base (Eq. 8.62).152... 

The indium-mediated allylation reaction in aqueous media has been applied to the studies on the total synthesis of dysiherbaine (Scheme 8.18).159... 

A chemoenzymatic methodology has been developed using indium-mediated allylation (and propargylation) of heterocyclic aldehydes under aqueous conditions followed by Pseudomonas cepacia lipase-catalyzed enantioselective acylation of racemic homoallylic and homo-propargylic alcohols in organic media.192... 

It was reported that the indium-mediated Michael addition of allyl bromide to l,l-dicyano-2-arylethenes proceeded well in an aqueous medium.55 Similarly, cyclopentadienylindium(I) was reported to add in... 

Allylation of acyloyl-imidazoles and pyrazoles61 with allyl halide mediated by indium in aqueous media provides a facile regioselective synthesis of P, y-unsaturated ketones (Scheme 11.1), which has been applied to the synthesis of the monoterpene artemesia ketone. The same product can be obtained by indium-mediated allylation of acyl cyanide (Eq. 11.35).62 Samarium, gallium, and bismuth can be used as a mediator for the allylation of nitrones and hydrazones to give homoallylic hydroxylamine and hydrazides in aqueous media in the presence of Bu4NBr (Scheme 11.2).63 The reaction with gallium and bismuth can be increased dramatically under microwave activation. 

Iminium ions, generated in aqueous solution from secondary amines and formaldehyde, undergo a Barbier-type allylation mediated by tin, aluminum, and zinc. The reaction is catalyzed by copper and produces tertiary homoallylamines in up to 85% yield.67 The imines generated in situ from 2-pyridinecarboxaldehyde/2-quinolinecarboxaldehyde and aryl amines undergo indium-mediated Barbier allylation in aqueous media to provide homoallylic amines.68 Crotyl and cinnamyl bromides... 

Indium-mediated allylation reactions of a-keto imides derived from Oppolzer s sultam proceeded in aqueous THF in good yields and excellent diastereoselectivity (Eq. 11.43).74 The indium-mediated allylation of the Oppolzer camphorsultam derivatives of glyoxylic oxime ether... 

Cleghorn LAT, Cooper IR, Grigg R, MacLachlan WS, Sridharan V (2003b) Additive effects in palladium-indium mediated Barbier type allylations. Tetrahedron Lett 44 7969-7973... 

Stereoselective allylation of aldehydes is another preferred strategy for the synthesis of appropriate intermediates for the total synthesis and introduction of hydroxy functionalities. Park and co-workers <2003S2473> proposed a synthesis of castanospermine 228 through a key indium-mediated allylation in the presence of (+)-cinchonine of an a-amino aldehyde 247 derived from D-glucono-O-lactone (Scheme 53). 

Indium-mediated diastereoselective allylation of L-glyceraldimines with4-bromo-1,1,1-trifluoro-2-butene provided stereoselectively, after further steps, enantiopure 4,4,4-trifluorovaline or 4,4,4-trifluoroisoleucine." ° Enantiopure hexafluorovahnes have been prepared by separation of the diastereomeric mixture resulting from the Michael addition of a chiral amine onto an ester of bis(trifluoromethyl) acryhc acid. Presence of the two CF3 groups reverses the orientation of the Michael addition (Figure 5.7)." ... 

Indium mediated allylation of 4-acetoxy-2-azetidinones gave the products 57 in high yield <99SL447> and similar reactions with azetidin-2,3-diones gave 3-substituted 3-hydroxy-P-lactams 58 <98H97>. 

Annnlation methodology based on indium-mediated allylation reactions in water (Li and Lu, 1996)... 

Indium mediates the coupling of a,a-difluoroallyl carbanion with aldehydes, to give geuz-difluorohomoallyl alcohols.89 hi contrast to many comparable allylations of carbonyl compounds, ketones do not react. 

Unsubstituted (3-lactams have instead been obtained, by the same authors, through indium-mediated reaction of imines with alkyl bromoacetates [52]. (3-Lactams having a wide range of substituents linked to the nitrogen atom, such as aryl, aryl alkyl, or allyl groups, could be prepared by this pathway. 

Dialkynyl ligands, in platinum(II) complexes, 8, 545 iV,iV-Diallylamine, via allyindium reagents, 9, 703-704 Diallyl clusters, in trirutheniums and triosmiums, 6, 773 gem-Diallyl esters, via indium-mediated allylation, 9, 677 Diallyl ethers, isomerization, 10, 90 Diamagnetic ylides, with gold(II), 2, 278 Diamides... 

Di(carbene)gold(I) salts, oxidation, 2, 293—294 Dicarbido clusters, with decarutheniums, 6, 1036 Dicarbollide amides, with tantalum, 5, 184 Dicarbollide thorium complexes, synthesis and characterization, 4, 224—225 Dicarbollyl ligands, in nickel complexes, 8, 185 Dicarbonyl complexes arylation with lead triacetates diastereoselectivity, 9, 389 enantioselectivity, 9, 391 mechanisms, 9, 387 reaction examples, 9, 382 indium-mediated allylation, 9, 675 with iridium, 7, 287 reductive cyclization, 10, 529 in Ru and Os half-sandwiches, 6, 508 with Zr—Hf(II), 4, 700... 

Grignard additions, 9, 59, 9, 64 indium-mediated allylation, 9, 687 in nickel complexes, 8, 150 ruthenium carbonyl reactions, 7, 142 ruthenium half-sandwiches, 6, 478 and selenium electrophiles, 9, W11 4( > 2 in vanadocene reactions, 5, 39 Nitrites, with trinuclear Os clusters, 6, 733 Nitroalkenes, Grignard additions, 9, 59-60 Nitroarenes, and Grignard reactivity, 9, 70 Nitrobenzenes, reductive aminocarbonylation, 11, 543... 

Otherwise, unsaturation may be introduced by use of carbonyl-containing carbohydrate derivatives and carbon nucleophiles that contain alkene (or, if desired, alkyne) functionality, a notable illustration being the tin-or indium-mediated C-l allylation of unprotected sugars. As an illustration, D-arabinose, treated with allyl bromide in aqueous ethanol in the presence of tin gives, after acetylation, 278 in 85% yield.258 In this procedure aldoses react better than do ketoses, and pentoses better than hexoses. More usual is the use of Grignard reactions to give, for example, the octynes 279. 

Yadav, J. S. Anjaneyulu, S. Ahmed, M. M. Reddy, B. V. S. Indium-mediated regioselective allylation of terminal epoxides a facile synthesis of bishomoallyl alcohols. Tetrahedron Lett. 2001, 42, 2557-2559. 

Indium mediates a highly enantioselective Barbier-type allylation of both aromatic and aliphatic aldehydes, using a chiral ethanolamine auxiliary, readily recoverable by acid extraction.193 Barbier coupling of aldehydes can be carried out in water using tin(II) chloride, with cobalt(II) acetylacetonate as catalyst.194... 

Indium mediated Barbier-type cross coupling between carbonyl compounds and allyl halides proceed efficiently under solvent-free conditions. No apparent competing pinacol-coupling or homo-coupling of the allyl halide was observed. The reactions were found to be mediated also by zinc, tin, bismut and copper [45]. 

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