Aldehydes Tsuji allylation

Thus, [HRh(C0)(TPPTS)3]/H20/silica (TPPTS = sodium salt of tri(m-sulfophenyl)phopshine) catalyzes the hydroformylation of heavy and functionalized olefins,118-122 the selective hydrogenation of a,/3-unsaturated aldehydes,84 and the asymmetric hydrogenation of 2-(6 -methoxy-2 -naphthyl)acrylic add (a precursor of naproxen).123,124 More recently, this methodology was tested for the palladium-catalyzed Trost Tsuji (allylic substitution) and Heck (olefin arylation) reactions.125-127... 

Tsuji J, Minami I, Shimizu I. Palladium-catalyzed allylation of ketones and aldehydes via allyl enol carbonates. Tetrahedron Lett. 1983 24 1793-1796. 

The preparation of a-lithio aldehydes, o -lithio ketones, and related compounds and their applications to organic synthesis has been reviewed.10 The Tsuji-Trost allylic alkylation with ketone enolates has been highlighted.11... 

Alkali metal enolates of ordinary ketones and aldehydes tend to fail to undergo the Tsuji-Trost allylation.37 However, it has been found that their enoxyborates and zinc enolates52 readily undergo the Pd catalysed allylation which proceeds with net retention just like the other examples of the... 

It is very well known that jr-allyl palladium complex 1, which is a key intermediate for the Tsuji-Trost type allylation, has an electrophilic character and reacts with nucleophiles to afford the corresponding allylation products. We discovered that bis 7r-allyl palladium complex 2 is nucleophilic and reacts with electophiles such as aldehydes [27] and imines [28-32] (Scheme 2, Structure 2). We have also shown that bis 7r-allyl palladium complex 2 can act as an amphiphilic catalytic allylating agent it reacts with both nucleophilic and electrophilic carbons at once to produce double allylation products [33]. These complexes incorporate two allyl moieties that can bind with different hapticity to palladium (Scheme 3). The different complexes may interconvert by ligand coordination. The complexes 2a, 2b and 2c are called as r]3,r]3-bisallypalladium complex (also called bis-jr-allylpalladium complex), r)l,r)3-bis(allyl)palladium complex, -bis(allyl)palladium complex, respectively. Bis zr-allyl palladium complex 2 can easily be generated by reaction of mono-allylpalladium complex 1 and allylmetal species 3 (Scheme 4) [33-36]. Because of the unique catalytic activities of the bis zr-allyl palladium complex 2, a number of interesting cascade reactions appeared in the literature. The subject of the present chapter is to review some recent synthetic and mechanistic aspects of the interesting palladium catalyzed cascade reactions which in-... 

Trost, B.M. Acc. Chem. Res. 1980,13, 385 Tsuji, J. Pure Appl. Chem. 1982, 54, 197. Catalysis of allyl-Sn additions to aldehydes by Pd(II)L2Cl2 complexes recently has been reported one, less efficient example using Pd(PPh3)4 was included. Nakamura, H. Iwama, H. Yamamoto, Y. J. Am. Chem. Soc. 1996,118, 6641. 

Although it is mechanistically different from the Tsuji-Trost allylation, indirect allyla-tions of ketones, aldehydes, and esters via their enolates are briefly summarized here. Related reactions are treated in Sect V.2.1.4. Pd-catalyzed allylation of aldehydes, ketones, and esters with aUyhc carbonates is possible via the Tr-allylpaUadium enolates of these carbonyl compounds. Tr-AUylpalladium enolates can be generated by the treatment of silyl and stannyl enol ethers of carbonyl compounds with allyl carbonates, and the allylated products are obtained by the reductive elimination of the Tr-allylpalladium enolates. 

Nucleophiles used in the seminal papers by Tsuji and co-workers were mostly stabilized carbon nucleophiles, and the method found an early synthetic application in a preparation of steroids." It soon became evident that many other types of nucleophiles could be used. In particular, hydride ion equivalents led to l-olefinsf ° " (see Sect. V.2.3.1), Silyl and stannyl enolates of simple ketones and aldehydes and esters can be aUylated, as well as allyl enol carbonates (see Sect. V.2.1.4), This is an indirect a-aUylation of ketones, aldehydes, and esters. Enol derivatives can take another reaction course under Pd(0) catalysis (Scheme 2). Thus, oxidation to a,/3-unsaturated carbonyl compounds ensues if reactions are performed in acetonitrile under precise sources of catalyst precursor. "" "" A full discussion on the dichotomy of allylation-oxidation has been published, as well as a comparison of the usefulness of several transition metals as catalysts in allylation of nucleophiles. ... 

Contrary to earlier notions that the Pd-catalyzed a-allylation of carbonyl compounds would be limited to those carbonyl compounds that are extrastabilized (the Tsuji-Trost reaction), the use of Zn, B in the forms of BRjK or Li + 2 BR3, where R = Et, and so on, Si, and Sn has been shown to permit the use of those enolates of ordinary ketones, aldehyde esters, and so on, where the pATj of the carbonyl compounds may be 20. In some cases, however, even lithium enolates can provide satisfactory results. Since most of the enolates mentioned above are derived via alkali metal enolates containing Li, Na, or K, these parent enolates should be tested before converting or modilying them with reagents containing other metals. 

Al(0)/BiCl3, Zn(0)/BiCl3, Fe(0)/BiCl3, and Mg/BiCl3d Bismuth-mediated allylation was found to be promoted by the presence of fluoride ion or sonication. Allylation of aldehydes carried out by electrochemically regenerated bismuth metal in an aqueous two-phase system was reported by Minato and Tsuji. ... 

In the Tsuji-Tnost reaction, an allylic acetate first oxidatively adds to the Pd(0) catalyst to give a n -allyl complex, which undergoes nucleqphilic attack by the carbanion derived from the deprotonated active methylene compound to give the coupled product allyl alcohols and aldehydes can be coupled by a related procedure. ... 

In the presence of bismuth(lll) chloride-aluminum, allylic bromides have been found to react with aldehydes at room temperature in tetrahydrofuran-water to afford the corresponding homoallyhc alcohols in high yields (Wada et al, 1987). Water was found to play a crucial role since the allylation failed in pure tetrahydrofuran. Only a catalytic amount of bismuth chloride was needed to carry out the reaction. Bismuth(ill) chloride was reduced by aluminum to zero-valent bismuth, which could insert into the carbon-bromine bond of the allylic bromide to afford an allylbismuth intermediate as the reactive species. The allylation reaction could occur with the couple Bi(0)-Al(0) in tetrahydrofuran-water only in the presence of a catalytic amount of hydrobromic acid (Wada et al, 1990). Since bismuth(O) was postulated to be an intermediate oxidation state, the reaction was accomplished via an electrochemical redox pathway (Figure 4.1) in a two-phase system (Minato and Tsuji, 1988). Reactions mediated by Bi(0) as the only promotor were sluggish (Wada et ah, 1990). An exception was, however, reported with the coupling between p-nitrobenzaldehyde and allyl iodide in water (Chan and Isaac, 1996). 

Minato, M. Tsuji, J. (1988) Allylation of aldehydes in an aqueous two-phase system by electro-chemically regenerated bismuth metal, Chem. Lett., 2049-52. 

List has developed the concept of asymmetric counter-ion directed catalysis and applied it in organocatalytic transformations. One of the first pioneering studies in the synergic use of organocatalyst and transition metal was the combination of a Pd(0) catalyst with a chiral phosphoric acid in a highly enantioselective Tsuji-Trost type a-allylation of branched aldehydes (Scheme 26.12) [81]. 

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