Hetero Diels-Alder reactions in synthesis

Hetero Diels-Alder reaction in synthesis of functionalized natural hetero-... 

The great importance of the Diels-Alder and hetero-Diels-Alder reactions in synthesis is a strong stimulus for finding new aspects about them, especially those methodologically related, and chiral catalysts rank high in such a context. Accordingly, 145, ID, and 146 are valuable additions to the list of the metal-free entities, even ID is somewhat inferior due to relatively low asymmetric induction (up to 70% ee) it tenders during the reaction of anthro-nes and maleimides. 

Nesi R., Giorni D. and Turchi S. Synthesis of Nitrogen Heterocycles hy Hetero Diels-Alder Reactions in Seminars in Organic Synthesis. 24th Summer Sch A. Corbella 1999 225, Ed. Trombini, Pb. Soc. Chim. Ital. 

An extensive review of the hetero-Diels-Alder reactions of 1-oxabuta-1,3-dienes has been published. Ab initio calculations of the Diels-Alder reactions of prop-2-enethial with a number of dienophiles show that the transition states of all the reactions are similar and synchronous.Thio- and seleno-carbonyl compounds behave as superdienophiles in Diels-Alder reactions with cyclic and aryl-, methyl-, or methoxy-substituted open-chain buta-1,3-dienes.The intramolecular hetero-Diels-Alder reactions of 4-benzylidine-3-oxo[l,3]oxathiolan-5-ones (100) produce cycloadducts (101) and (102) in high yield and excellent endo/exo-selectivity (Scheme 39). A density functional theoretical study of the hetero-Diels-Alder reaction between butadiene and acrolein indicates that the endo s-cis is the most stable transition structure in both catalysed and uncatalysed reactions.The formation and use of amino acid-derived chiral acylnitroso hetero-Diels-Alder reactions in organic synthesis has been reviewed. The 4 + 2-cycloadditions of A-acylthioformamides as dienophiles have been reviewed. ... 

R. R. Schmidt, Hetero-Diels-Alder reactions in highly functionalized natural product synthesis, Acc. Chem. Res. 19 250 (1986). 

Y. Chapleur and M.-N. Euvrard, Hetero Diels-Alder reactions in carbohydrate chemistry A new strategy for multichiral arrays synthesis, J. Chem. Soc. Chem. Commun. p. 884 (1987). 

Clearly, an important feature will be the selectivity of these reactions. In this respect, the control of endo- and exo-selectivity using different Lewis acids, the induced diastereoselectivity with chiral heterobutadienes as well as chiral heterodienophiles and finally the use of chiral Lewis acids for the enantioselec-tive synthesis will be discussed. In recent time some attention has been paid to hetero Diels-Alder reactions in aqueous solutions and in the presence of inor-... 

The combination of two all-carbon and one hetero Diels-Alder reaction in the presence of catalytic amounts of Eu(fod)3 of 2-2 and 2-3 to give 2-4 was used in the synthesis of vincomycinone B2 methyl ester 2-5, Scheme 2-2 [71]. 

Tietze LF, Kettschau G (1997) Hetero Diels-Alder Reactions in Organic Chemistry. 189 1 -120 Thiem J, Klaffke W (1990) Synthesis of Deoxy Oligosaccharides. 154 285-332 Thiem J, see Gambert U (1997) 186 21-43 Thomson RS, see Itzstein vonM (1997) 186 119-170... 

Tietze, L E, Kettschau, G, Hetero-Diels-Alder reactions in organic chemistry. In Topics in Current Chemistry Stereoselective Heterocyclic Synthesis I, Metz, P, Ed., Springer, Berlin, pp. 1-120, 1997. 

Parker, D. T. Hetero Diels-Alder reactions. Organic Synthesis in Water 1998,47-81. 

Swindeii, C. S., Tao, M. Chirai auxiiiary-mediated asymmetric induction in a thermai inverse eiectron demand hetero-Diels-Alder reaction. Enantioseiective synthesis of the taxoi A-ring side chain. J. Org. Chem. 1993, 58, 5889-5891. 

Danishefsky and coworkers employed two hetero Diels-Alder reactions in a total synthesis of the ansa bridge of rifamycin S (Scheme 52) The first cyclocondensation reaction uses the trimethylsilyloxy diene (14) and a preincubated solution of 3-(benzoyloxy)-2-methyl-1-propanal (188) with an excess of TiCU in CHCh. The product is exclusively the syn-ACF pyrone (189). Through a Ferrier rearrangement and a sequence of oxidation-reduction steps followed by functional group manipulations aldehyde (190) is obtained. 

Hetero-Diels-Alder reactions. Dihydropyran synthesis by the condensation of enones and vinyl ethers in the presence of Znlj is endo-selective. ... 

Polyoxygenated Natural Products , Aldrichimica Acta, 1986, 1959. R.R.Schmidt, Hetero-Diels-Alder Reaction in Highly Functionalised Natural Product Synthesis, Acc.Chem.Res., 1986, 19, 250. 

Hetero-Diels-Alder reaction/ Dihydropyran synthesis, in the manner reported by Danishefsky, from monoactivated dienes and aldehydes is best catalyzed by BF -OEtj. The Mukaiyama aldol condensation pathway does not operate in such cases. 

The Diels-Alder cycloaddition has played an important role in the synthesis of Narcissus alkaloids and related structures. Roger has prepared anhydrolycorinone using an intramolecular hetero-Diels-Alder reaction in which a 1,3,4-oxadiazole... 

Swindell CS, Tao M (1993) Chiral Auxiliary-Mediated Asymmetric Induction in a Thermal Inverse Electron Demand Hetero-Diels-Alder Reaction - Enantioselective Synthesis of the Taxol A-Ring Side Chain. J Org Chem 58 5889... 

The intramolecular Diels-Alder reaction is most frequently used in natural product total synthesis, and numerous examples will be described in the synthetic utility section. As with the intermolecular variant, intramolecular reactions are highly regioselective and stereoselective and participate in hetero, inverse electron demand, and asymmetric Diels-Alder reactions. One report from 2008 describes the investigation of an intramolecular hetero Diels-Alder reaction in ionic liquids. ... 

D.T. Parker, Hetero Diels-Alder Reactions, in Organic Synthesis in Water , Paul A. Grieco, Ed., Blackie Academic and Professional, New York, 1998, pp. 47-80. 

In a different approach to performing hetero Diels-Alder reactions in water, Pier-matti reported three-component aza Diels-Alder reaction of 2-cyclohexen-l-one, aniline and aldehyde in water in the presence of a-zirconium hydrogenphosphate (a-ZrP) and SDS for the synthesis of diaiyl-2-azabicyclo[2.2.2]octan-5-ones 53 [39], The reactions performed in water at room temperature had higher exo selec-tivities than in organic solvents (Scheme 1.26). 

Several heterodienes and heterodienophiles are used in hetero-Diels-Alder reactions in the synthesis of heterocyclic compounds. For example, aza-butadiene 81 and 81a and oxazoles 82 and 83 are used as heterodienes for synthesis of heterocycles. 

A range of substituents on the diene and the dienophile are tolerated and reactions proceed in high yields with high enantioselectivities. The authors have proposed a square-planar model (275) with acyl phosphonate or acyl ester coordinated to the Cu(II)/t-Bu-BOX (13) complex to account for the observed stereoselectivity. Stavenger and Schreiber also applied this approach to enan-tioselective hetero Diels-Alder reactions in a diversity-oriented synthesis of a library of dihydropyrancarboxamides [89]. Jorgensen and coworkers also reported Cu(II)/bisoxazoline-catalyzed hetero Diels-Alder reactions employing acyl esters... 

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