Spontaneous Absolute Asymmetric Synthesis
Spontaneous absolute asymmetric synthesis, that is the statistical formation of enantioenriched compounds from achiral reagents without the intervention of any chiral auxiliary, has been proposed as one of the origins of chirality. Without using any chiral substance, nucleophilic attack on a prochiral aldehyde on the Re- or Si-face occurs with an equal probability, providing S - and R -products with stochastic distribution, that is, so-called racemic modification. However, as Mislow described...
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Northrup, A. B. MacMillan, D. W. C. Science 2004, 305, 1752-1755. Casas, J. Engqvist, M. Ibrahem, I. Kaynak, B. Cordova, A. Angew. Chem. Int. Ed. For a recent review on the organocatalytic synthesis of carbohydrates, see Kazmaier, U. Angew. Chem. Int. Ed. 2005, 44, 2186-2188. For a recent review on the organocatalytic synthesis of carbohydrates, see Limbach, M. Chem. Biodiv. 2005, 2, 825-836. Pidathala, C. Hoang, L. Vignola, N. List, B. Angew. Chem. Int. Ed. 2003, 42, 2785-2788. 283. Cordova,...
Sprix Chemistry
4.3.3 Asymmetric Carbonylation of Carbon-Heteroatom Bonds A carbon-oxygen bond and a carbon-nitrogen bond in an epoxide and an aziridine can be cleaved by metal-catalyzed carbonylation giving a lactone and a lactam, respectively. Highly efficient kinetic resolution has been achieved in the reaction of racemic aziridines catalyzed by Rh COD Cl 2 in the presence of -menthol 3 equivalents to the aziridine .55 A carbon-halogen bond can be converted into the corresponding carbon-carbonyl bond via...
Enyne Metathesis
Ring-closing metathesis of an enyne, which has double and triple bonds in the molecule, is a remarkable reaction which is useful in synthetic organic chemistry. In enyne metathesis, the double bond is cleaved and carbon-carbon bond formation occurs between the double and triple bonds. The cleaved alkylidene part is moved to the alkyne carbon. Thus, the cyclized compound formed in this reaction has a diene moiety Eq. 6.77 .57 The reaction is also called skeletal rearrangement'' and is induced by...
REFERENCES AND NOTES Tke
1. Noyori R. Ed. , Asymmetric Catalysis in Organic Synthesis, Wiley, New York, 1994. 2. Jacobsen, E. N. Pfaltz, A. Yamamoto H. Eds. , Comprehensive Asymmetric Catalysis, Springer, Heidelberg, 1999. 3. Ojima I. Ed. , Catalytic Asymmetric Synthesis, 2nd ed., Wiley-VCH, New York, 2000. 4. Jacobsen, E. N. Pfaltz, A. Yamamoto H. Eds. , Comprehensive Asymmetric Catalysis. Supplement, Springer, Heidelberg, 2004. 5. For notable examples of organocatalytic reactions, see the following. Aldol reaction a...
O NHPMP Fgl
Michael Reactions301'304 The Michael and analogous conjugate addition reactions represent a cornerstone of classical and modern chemical synthesis, and not surprisingly, therefore, catalytic variants of this venerable reaction have received increasing attention in recent years.301_303,305 The first examples of enamine Michael additions using proline 2 as the organocatalyst have proven disappointing in terms of enantiocontrol,87,88,176,220,306_310 stimulating the search for a more selective...
Conclusion
The concept of nonlinear effects has evolved since its recognition in the mid-1980s only. The plot eeprod f eeau is now widely used as a tool to learn more about a catalytic system. The concepts and basic principles can been extended with some caution to kinetic resolution and to chiral reagents. Nonlinear effects that have been described thus far overwhelmingly for organometallic catalysts where aggregation processes or formation of multiligands species are easily understood. The renewal of...
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Melchiorre, P. J0rgensen, K. A. J. Org. Chem. 2003, 68, 4151-4157. Betancort, J. M. Sakthivel, K. Thayumanavan, R. Tanaka, F. Barbas III, C. F. Synthesis Ishii, T. Fujioka, S. Sekiguchi, Y. Kotsuki, H. J. Am. Chem. Soc. 2004,126, 9558-9559. Cobb, A. J. A. Longbottom, D. A. Shaw, D. M. Ley, S. V. Chem. Commun. 2004, 1808-1809. Mase, N. Thayumanavan, R. Tanaka, F. Barbas III, C. F. Org. Lett. 2004, 6, 2527-2530. Wang, W. Wang, J. Li, H. Angew. Chem. Int. Ed. 2005, 44, 1369-1371. Mitchell, C. E....
Introduction 1
The oxidation reaction is one of the most fundamental transformations in organic chemistry. Its catalytic enantioselective versions, compared with the reductions of unsaturated compounds, have more recently appeared as the common procedures for organic syntheses.1 In 1970, molybdenum or vanadium complexes2 were reported to catalyze the epoxidation of alkenes with peroxides as the terminal oxidants, and it was observed that the epoxidation of allylic alcohols was specifically enhanced by a...
Asymmetric Hydrocyanation Of Olefins
Over a billion pounds of adiponitrile is produced each year by hydrocyanation of butadiene. Asymmetric addition of hydrogen cyanide has been studied for activated olefins such as norbornene and vinylarenes using nickel complexes of phosphite-based ligands.70 Optically active a-arylpropionitriles, the products of asymmetric hydrocyanation of vinylarenes, can be transformed into a-arylpropa-noic acids, known as antiinflammatory drugs. The highest enantioselectivities have been obtained for the...
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Sunden, H. Ibrahem, I. Eriksson, L. Cordova, A. Angew. Chem. Int. Ed. 2005, 44, 4877-4880. List, B. Castello, C. Synlett 2001, 1687-1689. Ramachary, D. B. Chowdari, N. S. Barbas III, C. F. Synlett 2003, 1910-1914. Ramachary, D. B. Chowdari, N. S. Barbas III, C. F. Angew. Chem. Int. Ed. 2003, 42, 4233-4237. Ramachary, D. B. Anebouselvy, K. Chowdari, N. S. Barbas III, C. F. J. Org. Chem. 2004, 69, 5838-5849. B0gevig, A. Juhl, K. Kumaragurubaran, N. Zhuang, W. J0rgensen, K. A. Angew. List, B. J....
Alkyne Metathesis
In alkyne metathesis, the triple bond of an alkyne is cleaved and triple-bond construction occurs simultaneously.83 The first effective catalyst for alkyne metathesis was a heterogeneous mixture of tungsten oxide and silica.84 Then Mortreux found that Mo CO 6 and phenol is effective for alkyne metathesis. When an alkyne is heated with Mo CO 6 and resorcinol, a mixture of three alkynes is formed because the reaction is in a state of equilibrium under these conditions Eq. 6.116 .85 Although the...
Historical Background
The field of asymmetric organocatalysis has a longstanding history that begins in the early twentieth century see timeline in Figure 11.2 . Indeed, the first example of asymmetric organocatalytic reaction was reported by Bredig and Fiske in 1912.25 In these studies, cinchona alkaloids catalyzed the addition of hydrogen cyanide to benzaldehyde and later, the addition to other alde-hydes 26,27 affording optically active cyanohydrins with low enantiomeric excess lt 10 ee .25-27 Remarkably, it took...
Iminium Catalysis A New Concept In Organocatalysis
The Catalysis Concept of Iminium Activation In 2000, the MacMillan laboratory136 disclosed a new strategy for asymmetric synthesis based on the capacity of chiral amines to function as enantioselective catalysts for a range of transformations that traditionally use Lewis acids. This catalytic concept was founded on the mechanistic postulate that the reversible formation of iminium ions from a,p-unsaturated aldehydes and amines Eq. 11.10 might emulate the equilibrium dynamics and p-orbital...
CN Dxy
In the 1990s, short peptides,5 99 and other nucleophiles15,16,100-107 were used as organocatalysts for a number of enantioselective acyl transfer processes transformations that set the stage for the more recent research in the area of nucleophilic catalysis.15-21 One of the most appealing approaches to enantioselective acyl transfer was outlined by Fu using an azaferrocene catalyst 6 Eq. 11.6 .15,103-107 While these pyridyl systems are not organic catalysts in the strictest sense, these...
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Tanoi, T. Mikami, K. Tetrahedron Lett. 2005, 46, 6355-6358. Momiyama, N. Yamamoto, H. J. Am. Chem. Soc. 2005, 127, 1080-1081. Nelson, A. Angew. Chem. Int. Ed. 1999, 38, 1583-1585. O'Donnell, M. J. In Catalytic Asymmetric Synthesis, 2nd ed. Ojima, I. Ed. , Wiley-VCH, New York, 2000. Jones, R. A. Quaternary Ammonium Salts Their Use in Phase-Transfer Catalysis, Academic Press, London, 2001. Lygo, B. In Rodd's Chemistry of Carbon Compounds Asymmetric Catalysis, Vol. 5, 2nd ed., Sainsbury, M. Ed. ,...
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Uraguchi, D. Terada, M. J. Am. Chem. Soc. 2004, 126, 5356-5357. Akiyama, T. Morita, H. Itoh, J. Fuchibe, K. Org. Lett. 2005, 7, 2583-2585. Uraguchi, D. Sorimachi, K. Terada, M. J. Am. Chem. Soc. 2004, 126, 11804-11805. Rueping, M. Sugiono, E. Azap, C. Theissmann, T. Bolte, M. Org. Lett. 2005, 7, 3781-3783. Hoffmann, S. Seayad, A. M. List, B. Angew. Chem. Int. Ed. 2005, 44, 7424-7427. Storer, R. I. Carrera, D. E. Ni, Y. MacMillan, D. W. C. J. Am. Chem. Soc. 2006, 128, 84-86. For the reduction of...