Carbon nucleophiles, Tsuji-Trost reaction

The formation of chromane derivatives has also been realised in the palladium catalyzed intramolecular nucleophilic substitution of allyl carbonates (Tsuji-Trost reaction). In most cases the reaction is accompanied by the formation of a new centre of chirality. Using Trost s chiral ligand the ring closure was carried out in an enantioselective manner. The asymmetric allylation of the phenol derivative shown in 4.20. was achieved both in good yield and with excellent selectivity.23... 

The efficient catalytic cycle is ascribed to the characteristic feature that Pd(0) is more stable than Pd(II). Reactions of 7t-allylpalladium complexes with carbon nucleophiles are called Tsuji Trost reactions. In addition to Pd, other transition metal complexes, such as those of Mo [26], Rh [27] and other metals, are used for catalytic allylation. 

Pd° species and TPPTS are excellent catalysts for allylic substitution with a variety of nucleophiles (carbon and hetero nucleophiles) in nitrile-water media (Tsuji-Trost reaction eq. (9) [182, 183]). 

The water soluble vitamin (+)-biotin was synthesized by M. Seki and co-workers from L-cysteine in only 11 steps using inexpensive reagents and mild reaction conditions." The key ring forming step was an intramolecular allylic amination Tsuji-Trost reaction using a nitrogen nucleophile) of a cis allylic carbonate. As expected with a soft nucleophile, the allylation took place with an overall retention of configuration. 

Tsuji, J. Palladium-catalyzed nucleophilic substitution involving allylpalladium, propargylpalladium, and related derivatives the Tsuji-Trost reaction and related carbon-carbon bond formation reactions overview of the palladium-catalyzed carbon-carbon bond formation viart-allylpalladium and propargylpalladium intermediates, in Handbook of Organopalladium Chemistry for Organic Synthesis (ed. Negishi, E.-L), 2, 1669-1687 (John Wiley Sons, New York, 2002). 

Carbon-Carbon Bond Formation via Nucleophilic Attack on an n3-n Ligand the Tsuji—Trost Reaction 555... 

The Tsuji-Trost reaction is the Pd-catalyzed allylation of nucleophiles [105] with allylic halides, acetates, carbonates, etc. This transformation proceeds via intermediate allylpalladium complexes (e.g. 110), and typically proceeds with overall retention of stereochemistry. In addition, the trapping of the intermediate allylpalladium complex usually occurs at the least hindered carbon. A representative example of this transformation is shown below in an application to the formation of an 7V-glycosidic bond. Treatment of 2,3-unsaturated hexopyranoside 109 with imidazole in the presence of a Pd(0) catalyst... 

Leaving groups in the Tsuji-Trost reaction include acetates, halides, ethers, carbonates, sulfones, carbamates, epoxides, and phosphates. Reviews (a) Tsuji, J. In Handbook of Organopalladium Chemistry for Organic Synthesis, Negishi, E. deMeijere, A., Eds. Wiley-lnterscience New York, 2002 Vol II, Palladium-Catalyzed Nucleophile Substitution Involving Allyl Palladium, Propargyl-palladium and Related Derivatives, pp. 1669-1687. (b) Frost C. G. Howarth, J. Williams, J. M. J. Tetrahedron Asymmetry 1992, 3, 1089-1122. 

Palladium-catalyzed reactions have been widely investigated and have become an indispensable synthetic tool for constructing carbon-carbon and carbon-heteroatom bonds in organic synthesis. Especially, the Tsuji-Trost reaction and palladium(II)-catalyzed cyclization reaction are representative of palladium-catalyzed reactions. These reactions are based on the electrophilic nature of palladium intermediates, such as n-allylpalladium and (Ti-alkyne)palladium complexes. Recently, it has been revealed that certain palladium intermediates, such as bis-7i-allylpalladium, vinylpalladium, and arylpalladium, act as a nucleophile and react with electron-deficient carbon-heteroatom and carbon-carbon multiple bonds [1]. Palladium-catalyzed nucleophilic reactions are classified into three categories as shown in Scheme 1 (a) nucleophilic and amphiphilic reactions of bis-n-allylpalladium, (b) nucleophilic reactions of allylmetals, which are catalytically generated from n-allylpalladium, with carbon-heteroatom double bonds, and (c) nucleophilic reaction of vinyl- and arylpalladium with carbon-heteroatom multiple bonds. According to this classification, recent developments of palladium-catalyzed nucleophilic reactions are described in this chapter. 

Mechanistic consideration of the Wacker reaction, which is thought to involve nucleophilic attach of ethylene complexed with Pd by HjO, led to the discovery of a carbon-carbon bond-forming reaction of 1,5-cyclooctadiene-Pd ir-complex with ethyl malonate in the presence of Na2C03 by Tsuji et al. in 1965 ° (Scheme 3). Re-searchers admit that an analogy between the organopalladium derivatives in Scheme 3 and TT-allylpalladium complexes was drawn and exploited in the discovery of the reaction of TT-allylpalladium with malonate also in 1965 (Scheme 4). It is noteworthy that this reaction remained only stoichiometric in Pd for several years. Once its catalytic version f was developed, however, this reaction has been extensively developed by Tsuji,Trost, " and many others, as detailed in Sect. V.2. Today, it is widely referred to as the Tsuji-Trost reaction, and it represents one of the most widely investigated areas of the organopalladium chemistry (Scheme 4). 

The Tsuji-Trost reaction is the palladium-catalyzed substitution of allylic leaving groups by carbon nucleophiles. These reactions proceed via 7i-allylpalladium intermediates. 

The Pd-catalysed allylation of carbon nucleophiles with allylic compounds via Jt-aUylpaUadium complexes is called the Tsuji-Trost reaction [32]. Typically, an allyl acetate or carbonate (54) reacts with a Pd-catalyst resulting in displacement of the leaving group to generate a Jt-allylpalladium complex (55) that can undergo substitution by a nucleophile (56) (Scheme 4.14). In 1965, Tsuji reported the reaction of ti-aUylpaUadium chloride with nucleophiles such as enamines and anions of diethyl malonate and ethyl acetoacetate. A catalytic variant was soon reported thereafter in the synthesis of allylic amines [33]. In 1973, Trost described the alkylation of alkyl-substituted 7i-aUylpalladium complexes with methyl methylsulfonylacetate... 

One distinguishes palladium(0)- and palladium(ll)-catalysed reactions. The most common palladium(O) transformations are the Mizoroki-Heck and the cross-coupling transformations such as the Suzuki-Miyaura, the Stille and the Sonogashira reactions, which allow the arylation or alkenylation of C=C double bonds, boronic acid derivates, stan-nanes and alkynes respectively [2]. Another important palladium(O) transformation is the nucleophilic substitution of usually allylic acetates or carbonates known as the Tsuji-Trost reaction [3]. The most versatile palladium(ll)-catalysed transformation is the Wacker oxidation, which is industrially used for the synthesis of acetaldehyde from ethylene [4]. It should be noted that many of these palladium-catalysed transformations can also be performed in an enantioselective way [5]. 

The palladium(0)-catalysed nucleophilic substitution of allylic acetates, carbonates or halides, also known as the Tsuji-Trost reaction, is a powerful procedure for the formation of C—C, C—O and C—N bonds. One of the early impressive examples, where this transformation had been combined with a pallada-ene reaction, was developed by Oppolzer and Gaudin [126], Although, in general, the Tsuji-Trost reaction can be combined with other palladium-catalysed transformations, there are only a few examples where it is combined with a Mizoroki-Heck transformation. 

Palladium-catalyzed allylic substitution reactions, known as Tsuji-Trost reactions, are a well-established method for carbon-carbon bond forming processes [48]. The generally accepted mechanism for this reaction involves the oxidative addition of the allylic substrate to Pd(0) to provide a Jt-allylpalladium complex. The subsequent reaction of the electrophilic 7t-allylpalladium complex with the nucleophile affords the substituted product and Pd(0), which is regenerated to start the catalytic cycle (Scheme 7.26). 

The catalytic version of allylation of nucleophiles via 7r-allylpaUadium intermediates was discovered in 1970 using allylic esters and aUyl phenyl ethers as substrates (Scheme Formation of 7r-allylpaUadium complexes by oxidative addition of various allylic compounds to Pd(0) and subsequent reaction of electrophilic rr-allylpalladium complexes with soft carbon nucleophiles are the basis of the catalytic allylation. After the reaction, Pd(0) is regenerated, which undergoes oxidative addition to the allylic compounds again, making the whole reaction catalytic. The efficient catalytic cycle is ascribed to the characteristic feature that Pd(0) is more stable than Pd(II). Allylation of carbon nucleophiles with allyhc compounds via TT-allylpalladium complexes is called the Tsuji-Trost reaction. The reaction has wide synthetic applications, particularly for cyclization. " ... 

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