Olefin aziridine ring opening

When the ligand (5,5)-70 was used, methyl cinnamate (71) was converted to the corresponding aziridine (S,S)-72 in 63% yield with an ee of 94% , but the optimal conditions for the aziridination of the cinnamate esters cannot be reliably extrapolated to other acyclic olefins . Reductive ring opening of (S,S)-72 by transfer hydrogenation afforded the corresponding (/f)-methyl iV-(p-toluenesulphonyl)phenylalaninate [(R)-73] and established the absolute configuration of (S,5 )-72 . This latter reaction and other reactions of the... 

The asymmetric oxidation of organic compounds, especially the epoxidation, dihydroxylation, aminohydroxylation, aziridination, and related reactions have been extensively studied and found widespread applications in the asymmetric synthesis of many important compounds. Like many other asymmetric reactions discussed in other chapters of this book, oxidation systems have been developed and extended steadily over the years in order to attain high stereoselectivity. This chapter on oxidation is organized into several key topics. The first section covers the formation of epoxides from allylic alcohols or their derivatives and the corresponding ring-opening reactions of the thus formed 2,3-epoxy alcohols. The second part deals with dihydroxylation reactions, which can provide diols from olefins. The third section delineates the recently discovered aminohydroxylation of olefins. The fourth topic involves the oxidation of unfunc-tionalized olefins. The chapter ends with a discussion of the oxidation of eno-lates and asymmetric aziridination reactions. 

Pancralistatin, [29], The first asymmetric total synthesis of (+)-pancratistatin (94) was reported by Hudlicky 130,26], Thus the bromo olefin 114 (Scheme 15), obtained by a-addition of copper nitrenoid generated from (N-tosyiimino) phenyliodinane to 45, was debrominated to the olefinic aziridine 117. The latter underwent Irons 1,2-ring opening with diarylcyancuprate... 

Intramolecular aziridinations of the olefinic sulfonamides 297, by means of the iminoiodane derivatives 298, have recently been demonstrated (Scheme 85) (OOOL2327). Ring-opening reactions of the bi- and tricyclic sultams 299, thus obtained, with selected nucleophiles were explored and provide access to functionalized cyclic sulfonamides. 

Jacobsen reported in 1990 that Mnm complexes of chiral salen ligands (41) were the most efficient catalysts available for the enantioselective epoxidation of alkyl- and aryl-substituted olefins.118 This stimulated a rapid development in the chemistry and applications of chiral SB complexes, which offer promising catalytic applications to several organic reactions, such as enantioselective cyclopropanation of styrenes, asymmetric aziridination of olefins, asymmetric Diels-Alder cycloaddition, and enantioselective ring opening of epoxides.4,119... 

Aziridines (e.g., 17) have the potential to undergo heterolytic ring-opening at the C-2/C-3 bond (facilitated by C-2/C-3 acceptor substituents) leading to 1,3 dipoles (e.g., 18) which can be trapped by 1,3-dipolar cycloaddition to electron-deficient olefins (e.g., maleic anhydride) to give pyrrolidine derivatives (e.g., 19) [48] ... 

Thus, the asymmetric catalysis of cyanoethoxycarbonylation, cyanophosphoryla-tion, epoxidation of electron-deficient olefins, Michael reactions of malonates and (3-keto-esters, Strecker reaction of keto-imines, conjugate addition of cyanide to a, (3-unsaturated pyrrole amides, ring opening of meso aziridines with TMSCN and cyanosilylation of ketones (example shown below) have been successfully carried out using these complexes as asymmetric catalysts. 

Olefins have a rich history in organic chemistry and consequently there is a vast array of transformations available to this fundamental functional group. This chapter discusses the classic methods for stereoselective oxidations of olefins, spanning the range from diastereoselective [16-18] and enantioselec-tive [19-29] formation of epoxides to their asymmetric ring-opening reactions [30-33], stereoselective formation of aziridines [34—37], iodolactoniza-tions and other olefin cyclizations induced by electrophiles [38, 39], dihy-droxylations [40-49], and aminohydroxylations [47, 50] (Figure 9.1). 

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