Trost catalysis

B. M. Trost and T. R. Verhoeven, Organopalladium Compounds in Organic Synthesis and in Catalysis, in Comprehensive Organomelaltic Chemistry. Vol 8. Pergamon Press, Oxford, 1982, p. 799. 

Trost and Hachiya [140] studied asymmetric molybdenum-catalyzed alkylations. Interestingly, they noticed that the regioselectivity of this transformation performed with a non-symmetric allylic substrate varied according to the nature of the metal Pd-catalyzed substitutions on aryl-substituted allyl systems led to attack at the less substituted carbon, whereas molybdenum catalysis afforded the more substituted product. They prepared the bis(pyridylamide) ligand 105 (Scheme 55) and synthesized the corresponding Mo-complex from (C2H5 - CN)3Mo(CO)3. With such a catalyst, the allylic... 

Trost, B.M. (1995) Atom Economy. A Challenge for Organic Synthesis - Homogeneous Catalysis Leads the Way. Angewandte Chemie International Edition, 34, 259-281. 

In 1981, it was demonstrated (70) that anions of nitro compounds can be involved in C,C-coupling with allyl acetates at the allylic carbon atom with the use of metal complex catalysis. For many years, this observation did not come to the attention of chemists interested in the synthesis of cyclic nitronates. However, Trost demonstrated (71) that this process can be used in the synthesis of five-membered cyclic nitronates from olefins (18) containing two acyl groups in the different allylic positions (Scheme 3.21). 

Trost reported the synthesis of 1,4-dienes with ruthenium catalysis through regioselective carbometallation of alkynes with alkenes.51 Di- and trisubstituted olefins can also be obtained with arylboronic acids through an intermolecular process under rhodium,30 52 55 nickel,56 and palladium catalysis.57 Recently, Larock has reported an efficient palladium-catalyzed route for the preparation of tetrasubstituted olefins.58,59... 

The Tsuji-Trost reaction is the Pd(0)-catalyzed allylation of a nucleophile [48-51]. The NH group in imidazole can take part as a nucleophile in the Tsuji-Trost reaction, whose applications are found in both nucleoside and carbohydrate chemistry. Starting from cyclopentadiene and paraformaldehyde, cyclopentenyl allylic acetate 64 was prepared in diastereomerically-enriched form via a Prins reaction [52], Treating 64 with imidazole under Pd(0) catalysis provided the N-alkylated imidazole 65. 

There is little doubt that the discovery of a class of chiral catalysts by Trost, represented by 102 in Scheme 15, constitutes one of the most important recent developments in asymmetric catalysis. The total synthesis of aflatoxin B, depicted in Scheme 15,... 

The involvement of transition-metal allenylidene complexes in homogeneous catalysis was reported for the first time by B. M. Trost and co-workers in 1992 (Scheme 35) [293-295]. The catalytic reactions allowed the preparation of a wide variety of tetrahydropyranyl and furanyl p,y-unsaturated ketones starting from hydroxy-functionalized alkynols and allylic alcohols, the key step in the catalytic... 

Trost s group reported direct catalytic enantioselective aldol reaction of unmodified ketones using dinuclear Zn complex 21 [Eq. (13.10)]. This reaction is noteworthy because products from linear aliphatic aldehydes were also obtained in reasonable chemical yields and enantioselectivity, in addition to secondary and tertiary alkyl-substituted aldehydes. Primary alkyl-substituted aldehydes are normally problematic substrates for direct aldol reaction because self-aldol condensation of the aldehydes complicates the reaction. Bifunctional Zn catalysis 22 was proposed, in which one Zn atom acts as a Lewis acid to activate an aldehyde and the other Zn-alkoxide acts as a Bronsted base to generate a Zn-enolate. The... 

Beside the Friedel-Crafts-type alkylation of arenes, the direct functionalization of 2,4-pentanediones is of great interest in Lewis acid catalysis. Although Pd-catalyzed Tsuji-Trost type allylations of 1,3-diketones are known, direct benzylation procedures catalyzed by Lewis acids are less explored [40-43]. Based on the previously described Friedel-Crafts alkylation of arenes and heteroarenes, the Rueping group developed a Bi(OTf)3-catalyzed benzylation of 2,4-pentanediones. Alcohols such as benzyl, allyl or cinnamyl alcohols were used as the electrophilic component to yield important 2-alkylated 1,3-dicarbonyl compounds. Initially, different Bi(III) salts were screened. In contrast... 

An effective method for the regioselective formation of chromenes has been reported by Subburaj et al. using base-catalyzed conditions (Equation 38) <1997J(P1)1875>. Trost < / /. have shown that pyranocoumarins can be synthesized using palladium catalysis, although regioselectivity problems are encountered (Equation 39 Table 7) <2003JA4518>. 

Trost, B.M. (2004) Asymmetric catalysis An enabling science. Proc. Natl. Acad. Sci. U.S.A., 101, 5348-5355 Noyori, R. (2002) Asymmetric catalysis Science and opportunities (Nobel Lecture). Angew. Chem., Int. Ed., 41. 2008-2022. 

Colonge Brvnie Bull. Soc. Chim. Fr. 1963, 1799. For an example with basic catalysis, see Hoffmann Kover. Pauluth J. Chem. Soc., Chem. Common. 1985, 812. For an example with a ruthenium complex catalyst, see Trost Kulawiec Tetrahedron Lett. 1991,32, 3039. 

American Chemical Society, Washington, DC (d) Trost, B.M. (1991) Comprehensive Organic Synthesis I, Fleming Pergamon, Oxford (e) Parshall, G.W. and Ittel, S.D. (1992) Homogeneous Catalysis, 2nd edn, John Wiley Sons, New York. 

The desymmetrization of dicarbonate 206 was initiated by the addition of one equivalent of N-(3-butenyl) nosylamide 207 under palladium catalysis in the presence of Trost s chiral diphosphine ligand 205. When the first allylic substitution was completed, the reaction was warmed and the resulting intermediate 208 was treated in situ with one equivalent of a second nosylamide 209. Product 210 resulting from this double substitution reaction was submitted to a tandem intramolecular ROM/RCM to furnish key precursor 211, which was engaged in the final cyc-lization step by the reduction of the double bonds, followed by the HCl-promoted domino deprotection of the acetal and aminal formation. 

With 1-alkoxyallenes as proelectrophiles, the palladium-catalysed asymmetric allylic alkylation proceeds with 1,3-dicarbonyl compounds as pronucleophiles with excellent regioselectivity good enantioselectivity (82-99% ee) was obtained with the Trost lig- and. The pH of the medium proved crucial for the reactivity and selectivity. By using the more acidic Meldrum s acids, the reactions required a co-catalytic amount of a Brpnsted acid, such as CF3CO2H. On the other hand, the less acidic 1,3-diketones failed to react under these conditions but the reaction proved to occur in the presence of the weaker benzoic acid, suggesting the need for general base catalysis. Indeed, a mixture of Et3N and PhCOiH proved to be optimal (93-99% ee). A mechanistic model to rationalize these results has been developed.88... 

The move toward catalytic reactions is reflected in the increase in the number of chapters in this book on the topic compared to the first edition. The trend has been observed by noted chemists in the previous decade. Professor Seebach, for example, in 1990 stated the primary center of attention for all synthetic methods will continue to shift toward catalytic and enantioselective variants indeed, it will not be long before such modifications will be available for every standard reaction. 6 Professor Trost in 1995 was a little more specific with catalysis by transition metal complexes has a major role to play in addressing the issue of atom economy—both from the point of view of improving existing processes, and, most importantly, from discovering new ones. 7 However, the concept can be extended to biological and organic catalysts and to those based on transition metals. 

In one of the first papers on the subject, Billups et al. (80SC147) reported that the Pd(0)-catalyzed allylation of indole 96 with allyl acetate gave N-allyl- (97) and 3-allylindole (98) plus the diallylation product 99 (Scheme 21). They also showed that the yV-allyl isomer 97 rearranged under Pd(0) catalysis to the C-3 isomer 98, thus indicating that the formation of 98 was thermodynamically controlled (C > N). The work of Billups also includes the use of allyl alcohol instead of allyl acetate in the Tsuji-Trost reaction. 

The Pd(0)-catalyzed allylation of 96 with acrolein dimethyl acetal gives exclusively compound 104. The 7j3-allylpalladium cationic complex (4, R = OMe) is attacked only at the center bearing the substituent MeO (80SC147), thus emphasizing the importance not only of steric effects in the electrophile but also of the electronic effects in the Tsuji-Trost reaction (92T1695). Indole 96 has been also allylated with epoxide 105 under Pd(0) catalysis by Trost and Molander (81JA5969). The intermediate cationic complex is attacked at the exocyclic position, 106 being formed, as shown in Scheme 22. 

For reviews of asymmetric catalytic epoxidations, see (a) R.S. Johnson, K.B. Sharpless, in B.M. Trost, I. Flemming (Eds.), Comprehensive Organic Synthesis, Vol. 7, Pergamon Press, New York, 1991 (b) R. Noyori, Asymmetric Catalysis in Organic... 

The synthesis of quaternary amino acids 86 have been shown using azlac-tones 85 as nucleophiles and the Trost ligand 39 under palladium [179] or molybdenum catalysis (Scheme 8) [180]. The allylic alkylation of glycine imino esters under biphasic conditions has also been achieved using a chiral phase-transfer catalyst in combination with an achiral Pd catalyst producing the unnatural amino acid derivatives [181]. 

Trost s synthesis138 of desethylibogamine (233) illustrates the application of a new approach to alkaloid synthesis, in which the two vital cyclization processes involve catalysis by palladium complexes protection of the nitrogen by formation of an amide, so often necessary in conventional syntheses, is here unnecessary. The first of the cyclization processes, (234)—>(235), results in a very neat formation of the isoquinuclidine ring system via a palladium-catalysed SN2 cyclization of the tryptamine derivative (234) (Scheme 24). 

Asymmetric catalysis August issue of Chem. Rev. 2003 and Proceedings Nat. Acad. Sciences, Asymmetric Catalysis Special Feature part I, 2004,101, 5347 and part II, ibidem, p. 5723 B. M. Trost and M. L. Crawley, Chem Rev. 2003, 103, 2921. 

Trost, E.M. and Fischer, L. (2002) Minimization of by-product formation during D-aminoadd oxidase catalyzed racemate resolution of D/L-amino adds. Journal of Molecular Catalysis B ... 

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