Addition of Allyl Groups

It was reported that the indium-mediated Michael addition of allyl 

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Many methods have been reported for the addition of allylic groups, including allyltrialkyltin compounds" (in the presence of BF3-etherate), as well as other allylic metal compounds." Allylic alcohols and homo allylic alcohols add to aldehydes in the presence of Sn(OT02 " For allylic halides, both activated... 

Nucleophilic Addition of Allylic Groups from Boron Compounds... 

The reaction can be applied to imines. Recently, the preparation of chiral allylglycines was effected by addition of allyl groups to the C=N bond in glyoxylic acid oximes modified as chiral sultams (Oppolzer chiral induction methodology).55 The yields (> 88%) and the diastereoselectivity (d.e. > 80 20) are excellent. 

Cyclopentadienyl complexes of molybdenum have also been used in asymmetric synthesis, mainly for the addition of allyl groups to carbonyl compounds (Section D. 1.3.3.3.). The chiral ligand was prepared from (—)-menthone via menthyl tosylate (see Section 3.5.1. for the alcohol)49 and introduced in an allylmolybdenum complex to give 1950. For an early review on catalytic applications of such compounds, see ref 51. 

A systematic study has shown that one of the best methods for effecting Michael additions of allyl groups to unsaturated esters is to use a combination of allyltrimethylsilane and fluoride ion both... 

Allyl ligands are reactive groups in catalytic processes, such as allylic substitution (Chapter 20) and transition-metal-catalyzed additions of allyl groups to carbonyl compounds (Chapter 12). They are also intermediates in a variety of catalytic processes involving dienes, including the hydroamination (Chapter 16) and telomerization of dienes (Chapter 22). They are also formed by cleavage of the allylic C-H bonds of olefins to form intermediates in allylic oxidation chemistry and as stable species that inhibit the polymerization of a-olefins (Chapter 22). The synthesis, structure, and occurrence of -rj -allyl complexes have been reviewed. ... 

Takuwa, A., Nischigaichi, Y., and Iwamoto, H., Conjugate addition of allylic groups to a, 3-enones via photoinduced electron transfer reaction of allyl stannanes, Chem. Lett., 1013, 1991. 

Even if hundreds of chiral catalysts have been developed to promote the enantioselective addition of alkylzinc reagents to aldehydes with enantioselectivities over 90% ee, the addition of organozinc reagents to aldehydes is not a solved problem. For example, only very few studies on the addition of vinyl groups or acetylides and even arylzinc reagents to aldehydes have been published, in spite of the fact that the products of these reactions, chiral allylic, propargylic and aryl alcohols, are valuable chiral building blocks. 

Reactions proceeding through open TS In this group, exemplified by BF3-catalyzed additions of allylic silanes and stannanes, the degree of stereochemical control is variable and often moderate. The stereoselectivity depends on steric factors in the open TS and can differ significantly for the E- and Z-isomers of the allylic reactant. 

There are few reports of oxidative addition to zerovalent transition metals under mild conditions three reports involving group 10 elements have appeared. Fischer and Burger reported the preparation of aTT -allylpalladium complex by the reaction of palladium sponge with allyl bromide(63). The Grignard-type addition of allyl halides to aldehydes has been carried out by reacting allylic halides with cobalt or nickel metal prepared by reduction of cobalt or nickel halides with manganese/iron alloy-thiourea(64). 

The addition of a large excess of bis(cj-alkenyl)zinc compounds to the TiC -catalyzed polymerization of propene resulted in an increased polymer yield, but a reduction in the molecular weights of the polymers.64 This suggests that the diorganozinc compounds are both co-catalysts and chain-transfer agents in this polymerization. The catalyst activity decreased in the order bis(3-butenyl)zinc < bis(7-octenyl)zinc < chlorodiethylaluminum. Bis(7-octenyl)zinc was co-polymerized with propene to afford hexylzinc side chains, whose zinc-carbon moieties were converted to vinyl groups by the addition of allyl bromide. 

Although the allylation reaction is formally analogous to the addition of allylboranes to carbonyl derivatives, it does not appear to occur through a cyclic transition state. This is because, in contrast to the boron in allyl boranes, the silicon in allylic silanes has no Lewis acid character and would not be expected to coordinate at the carbonyl oxygen. The stereochemistry of addition of allylic silanes to carbonyl compounds is consistent with an acyclic transition state. Both the E- and Z-stereoisomers of 2-butenyl(trimethyl)silane give the product in which the newly formed hydroxyl group is syn to the methyl substituent.64 The preferred orientation of approach by the silane minimizes interaction between the aldehyde substituent R and the methyl group. 

In earher work, the Hall group found that catalytic amounts of triflic acid promoted the addition of aUylboronates to aldehydes [132], While aUylboration reactions catalyzed by chiral Lewis acids in general led to only low levels of enan-tioselection [133], Hall found that chiral LBA 1 catalyzes the asymmetric addition of allyl- and crotylboronates to various aldehydes to provide products in excellent yields and moderate to high ee s (Scheme 5.71) [134]. Further, double diastereose-lective crotylboration could also be achieved with high selectivities using the... 

Trust s group has shown that another selective reaction involving C—O bond formation followed by rearrangement and C—C bond formation occurred when Cp-containing ruthenium complexes were used as catalytic precursors. With RuCl(Cp)(PPh3)2 in the presence of NH4PF6, an additive known to facilitate chloride abstraction from the metal center, the addition of allylic alcohols to terminal alkynes afforded unsaturated ketones [46, 47]. It has been shown that the key steps are the... 

Chelating alkylphosphanes that are water soluble by virtue of having hydroxy end groups were reported recently. The catalytic formylation of H2PC6H4PH2 and of H2PCH2CH2PH2 in the presence of formaldehyde in aqueous media yields hydroxymethyl bis(phosphanes) in near-quantitative yields (54). Hydroxypropyl-substituted compounds were prepared by radical addition of allylic substrates to 1,2-diphosphinoethane in methanol (55). 

Palladium acetate triarylphosphine complexes catalyze the addition of vinylic groups from vinylic halides to olefinic compounds in the presence of amines. Conjugated dienes are major products from 0,/3-unsaturated acids, esters, or nitriles while unactivated olefinic compounds react best in the presence of secondary amines where allylic amines are major products. The reactions are usually regio- and stereospecific. The synthetic utility of the reaction is illustrated with a wide variety of examples. 

Conjugate addition of acyl groups to naphthoquinones (3, 211).2 The acyl nickel carbonylate anion (1) undergoes conjugate addition to the ethylene ketal 2 to form a lithium adduct that can be trapped by allyl iodide to give 3 in 81% yield. This product can be converted in a few steps to the hydroxyquinone 4, a precursor of the naphthoquinone antibiotic deoxyfrenolicin (5). 

Kinetic resolution can be accomplished by addition of allyl boronates to aldehyde groups adjacent to the tricarbonyliron fragment [59]. For the synthesis of ikaruga-mycin, Roush and Wada developed an impressive asymmetric crotylboration of a prochiral meso complex using a chiral diisopropyl tartrate-derived crotylborane (Scheme 1.25) [60]. In the course of this synthesis, the stereo-directing effect of the tricarbonyliron fragment has been exploited twice to introduce stereospedfically a crotyl and a vinyl fragment. 

A chemoselective addition of allylic alcohols (82) to 3-halogenovinyl sulfones (81) has been accomplished using KF-basic alumina as the basic medium.55 The resulting adducts (83) can be stereoselectively cyclized by a radical process, affording 2,4-disubstituted tetrahydrofurans (84) (Scheme 22, Eq. 1). The same group has recently reported an analogous protocol using allylic amines (85) for the synthesis of 2,4-disubstituted pyrrolidines (87) (Scheme 22, Eq. 2)56... 

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