Coupling Tsuji—Trost

In addition to the applications reported in detail above, a number of other transition metal-catalyzed reactions in ionic liquids have been carried out with some success in recent years, illustrating the broad versatility of the methodology. Butadiene telomerization [34], olefin metathesis [110], carbonylation [111], allylic alkylation [112] and substitution [113], and Trost-Tsuji-coupling [114] are other examples of high value for synthetic chemists. 

Many organic chemical transformations have been carried out in ionic liquids hydrogenation [4, 5], oxidation [6], epoxidation [7], and hydroformylation [8] reactions, for example. In addition to these processes, numerous synthetic routes involve a carbon-carbon (C-C) bond-forming step. As a result, many C-C bondforming procedures have been studied in ambient-temperature ionic liquids. Among those reported are the Friedel-Crafts acylation [9] and allcylation [10] reactions, allylation reactions [11, 12], the Diels-Alder reaction [13], the Heck reaction [14], and the Suzuld [15] and Trost-Tsuji coupling [16] reactions. 

Trona deposits, sodium carbonate from, 22 787, 788-790 Tropane, 2 79 Tropical bleach, 4 45, 52 Tropical fishes aquaculture, 3 183 Troposphere, 22 526 Tropospheric ozone, 27 790-793 as greenhouse gas, 2 806, 807t Trost-Tsuji coupling reaction ionic liquids in, 26 890-891 Troubleshooting, technical service and, 24 341-342 Trousers (dress/sport)... 

There are many reports of benefits resulting from high solubilities of substrates. One example is the biphasic Trost Tsuji coupling (Scheme 16) involving [BMIM]C1... 

Promising results have been reported by various laboratories since 1990 on catalysis in molten salts, notably for catalytic hydrogenation, hydroformylation, oxidation, alkoxycarbonylation, hydrodimerization/telomerization, oligomerization, and Trost-Tsuji coupling [113]. A continuous-flow application to the linear dimerization of 1-butene on an ionic-liquid nickel catalyst system reached activities with TON > 18000 [116]. 

Trost-Tsuji-coupling 252,319 tungsten 246, 297 ff., 300 ff. tumoveror frequency (TOF) 234,... 

Finally, it should be mentioned that Pd-catalyzed allylations [230,231], allylic alkylation [231] and substitution [232] reactions as well as Trost-Tsuji-coupling [233] have also been carried out in different ionic liquids with some success. 

De BeUefon C, PoUet E, Grenouillet P (1999) Molten salts (ionic liquids) to improve the activity, selectivity and stahUity of the palladium catalysed Trost-Tsuji C-C coupling in biphasic media. J Mol Catal A Chem 145 121-126... 

The catalytic activity, selectivity, and catalyst stability is improved for Trost-Tsuji G-G coupling of cinnamyl carbonate and ethyl acetoacetate with a water-soluble Pd/TPPTS catalyst (sodium salt) when performed in [G4GiIm]Gl. " These Pd-catalyzed allylation reactions can also be performed under microwave conditions employing mixtures of [G2GiIm]BF4/water. ... 

Many transition metal-catalyzed cross-couplings such as the Stille coupling, the Heck reaction, the Suzuki reaction, and the Trost-Tsuji reactions have been carried out in aqueous conditions.In oiu own studies, we recently discovered that various palladium-catalyzed couplings of the above types can be performed in air and water. For example, a highly... 

Cellulose is a natural biopolymer, which is biodegradable, environmentally safe, widely abundant, inexpensive, and easy to handle [57]. Cellulose and its derivatives are widely used in chemical and bio-chemical applications and also as supports for the synthesis of organic molecules [58]. Interestingly, the cellulose fibers also act as a nanoreactor for the stabilization of metal nanoparticles [59]. However, its use as a support for catalytic applications is not well explored. Recently, Choplin and coworkers reported cellulose as the support for water soluble Pd(OAc>2/5 TPPTS system in the Trost-Tsuji allylic alkylation reaction [60]. To corroborate the above concept in the cross coupling of aryl halides and boronic acids, we reported A-arylation of imidazoles with aryl halides using a cellulose-supported Cu(0) catalyst (CELL-Cu(O) [61]. The prepared catalyst was well characterized using various instrumental techniques. For example, the X-ray diffraction pattern of CELL-Cu(O) catalyst clearly indicates the presence of Cu (111) and Cu (200) phases which are attributed to Cu(0) [46]. Further, the high resolution XPS narrow scan spectrum of the fresh CELL-Cu(O) catalyst shows a Cu 2p3/2 peak at 932.72 ev, which is attributed to Cu (0) [22]. 

Transition metal-catalyzed transformations are of major importance in synthetic organic chemistry [1], This reflects also the increasing number of domino processes starting with such a reaction. In particular, Pd-catalyzed domino transformations have seen an astounding development over the past years with the Heck reaction [2] - the Pd-catalyzed transformation of aryl halides or triflates as well as of alkenyl halides or triflates with alkenes or alkynes - being used most often. This has been combined with another Heck reaction or a cross-coupling reaction [3] such as Suzuki, Stille, and Sonogashira reactions. Moreover, several examples have been published with a Tsuji-Trost reaction [lb, 4], a carbonylation, a pericyclic or an aldol reaction as the second step. 

Inspection of Table 1 indicates that acylation, cyanation and enolate substitution represent the other classes of Pd- or Ni-catalyzed cross-coupling. The vast topic of Pd-catalyzed enolate -substitution including the Tsuji-Trost reaction and other -substitution reactions22 is not discussed in this chapter, and the readers are referred to pertinent reviews including that cited above. The other topics are very briefly discussed below. 

The palladium catalyzed intramolecular nucleophilic substitution of allyl alcohol derivatives (Tsuji-Trost reaction) has successfully been extended to the closure of a seven membered ring. The coupling of the allyl alcohol unit and the enamide was the key step in the preparation of the natural product claviciptic acid (5.14.),14... 

The Pd(0)-catalyzed allylic alkylation developed by Tsuji and Trost is useful for creating organic frameworks that have a variety of polar functional groups (197). The reaction is formally viewed as a combination of an allylic cation and a carbanion. A number of allylic compounds that have an electronegative leaving group can be coupled with stabilized cafbanions of pKa less than 16 under mild reaction conditions (Scheme 84). Nucleophilic attack of Pd(0) species on an allylic substrate... 

Tsuji-Trost allylation reactions offer multiple pathways to tetrahydrofuran synthesis including C-C bond-formation steps. A palladium-catalyzed sequence of allylic alkylation and Hiyama cross-coupling provides a convenient synthesis of 4-(styryl)-lactones (Scheme 67) <2006SL2231>. 

We conclude that the addition of phosphanes to palladium(II)-NHC complexes is advantageous with respect to reaction times, yield and completion ratio for a wide range of catalytic coupling reactions including Tsuji-Trost, allylic amination, Suzuki-Miyaura, Heck and Stille. 

Over the past 30-1- years, cross-coupling protocols utilizing a wide variety of metals and metalloids have been studied. However, we will cover only those that have been applied the most often in organic synthesis. Furthermore, the related Heck (see Heck Reaction) and Tsuji-Trost reactions, which follow different mechanisms (and hence, do not fall under our more narrow definition), are beyond the scope of this entry. 

Negishi, E.-i. Palladium-catalyzed cross-coupling involving 3-hetero-substituted compounds. Palladium-catalyzed a-substitution reactions of enolates and related derivatives other than the Tsuji-Trost allylation reaction. Handbook of Organopalladium Chemistry for Organic Synthesis 2002, 1, 693-719. 

In 2006 Fukuyama published a total synthesis of racemic morphine starting from isovanillin and a cyclohexene-epoxide [16, 17]. The key features in their synthesis are (1) a construction of the ether linkage between A and C rings by Tsuji-Trost coupling, (2) an intramolecular Heck reaction to construct A-C-E tricyclic system, and (3) an intramolecular Mannich-type reaction of a ketone with an aminal to provide the pentacyclic structure of morphine in a one-step reaction by double cyclization. 

The variety of carbon fragments that can join and the general tolerance of the reaction conditions to functional groups already present on these fragments lead to countless possibilities for rapid construction of complex molecules, especially biologically active compounds. One key difference between cross-coupling reactions and the Tsuji-Trost allylation or Heck olefination is the occurrence of a transmetalation step during the catalytic cycle. 

Scheme 11.3 Pd-catalyzed Tsuji-Trost reactions via C—H coupling.

Palladium-catalyzed nucleophilic substitution of allylic substrates (Tsuji-Trost coupling) is a most important methodology in organic synthesis and therefore it is no wonder that such reactions have been developed also in aqueous systems. Carbo- and heteronucleophiles have been found to react with allylic acetates or carbonates in aqueous acetonitrile or DMSO, in water or in biphasic mixtures of the latter with butyronitrile or benzonitrile, affording the products of substitution in excellent yields (Scheme 6.19) [7-11,14,45,46], Generally, K2C03 or amines are used as additives, however in some cases the hindered strong base diazabicycloundecene (DBU) proved superior to other bases. 

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