Allylation Tsuji

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... 

Many neoclerodanes, including 1 contain a trans-decalin core. In their attempt to synthesize 1, Bums and Forsyth have developed a synthetic strategy to establish the core through an intramolecular Diels-Alder/Tsuji allylation sequential sequence... 

Bums A, Forsyth C (2008) Intramolecular Diels-Alder/Tsuji allylation assembly of the functionalized trans-decalin of salvinorin A. Org Lett 10 97-100... 

Recent results have appeared related to the use of a new bio-support for SAPC. The authors report the first example of a palladium complex containing TPPTS supported on cellulose, a natural polysaccharide. The cellulose powder, which presents a specific surface area of 1.35 m and 3 wt% water content with [Pd(TPPTS)3] formed in situ, is an efficient support for the Trost-Tsuji allylic alkylation reaction [29]. 

Enantioselective Tsuji Allylations Mohr, J.T. Stoltz, B.M. Chemistry Asian J. 2007, 2, 1476. 

Scheme 4.15 Tsuji allylation reactions from a variety of precursors...

Asymmetric Induction on the Nucleophile The use of the tBu-PHOX ligand led to the first catalytic enantioselective Tsuji allylations of simple alkanone enol derivatives 62. These mild, operationally straightforward and stereoselective reactions described by Stoltz et al. [52] produce chiral cycloalkanones 63 with quaternary stereocenters at the a-position with high enantiopurities and in excellent chemical yields (Scheme 12.31). Mechanistic studies showed the incorporation of an O-bound enolate in the intermediate Pd-allyl complex [53]. Further investigations on the substrate scope led to several applications in the synthesis of natural products [54]. Recently, a similar approach was used to afford enantiopure quaternary lactams 65 that intercept synthetic intermediates previously used in the synthesis of the Aspidospcrma alkaloids quebrachamine and rhazinilam, but that were previously only available by chiral-auxiliary-assisted approaches or as racemic mixtures (Scheme 12.32) [55],... 

Palladium-Catalyzed Asymmetric Tsuji Allylation of Allyl Enol Carbonates... 

Table 1 Initial screening of chiral ligands in the Tsuji allylic alkylation...

Table 2 Non-PHOX ligands synthesized and tested in the asymmetric Tsuji allylation...

Tsuji Allylation A significant contribution to the field of asymmetric ketone alkylation is the Tsuji allylation. This method represents one of the only catalytic methods for asymmetric alkylation that has been suitably successful for application in the context of complex natural products. Significantly, this method also allows for the formation of all carbon quaternary stereocenters. 

Allyl Enol Carbonates In 2004, the Stoltz group introduced the first enantioselective Tsuji allylation from allyl enol carbonate substrates (Scheme 7.22)." " They found that the use of t-Bu-PHOX 132 ligand provided both high enan-tioselectivity and yield, generating 2-methyl-2-allylcyclo-hexanone in 90% yield and 89% ee. Expansion of the scope allowed for incorporation of branched allyl components as well as for a variety of substituents at the 2-position... 

SCHEME 7.22. First report of enantioselective Tsuji allylation. 

SCHEME 7.23. Trost et al. s enantioselective Tsuji allylation, including formation of tertiary stereocenters. 

Silyl Enol Ethers A disadvantage of the aforementioned enantioselective Tsuji allylations was that they were performed in an intramolecular fashion, requiring the need to synthesize the allyl enol carbonate starting materials. Although their synthesis is not overly cumbersome, the... 

SCHEME 7.25. Intermolecular Tsuji allylation using silyl enol ethers. 

Synthetic Applications The enantioselective Tsuji allylation represents one of the only catalytic, enantioselective... 

SCHEME 7.26. Tsuji allylation using allyl (3-ketoesters. 

Experimental procedure enantioselective Tsuji allylation in dichroanone... 

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]. 

Computational simulation of asymmetric Tsuji allylation involving prochiral nucleophiles and nonprochiral allyl fragments has proved to be consistent with experimental findings (Scheme 182). " ... 

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