Scandium—Bipyridine‐Catalyzed Enantioselective Addition of Alcohols and Amines to meso‐Epoxides.

Abstract

Ring opening reactions O 0132Scandium-Bipyridine-Catalyzed Enantioselective Addition of Alcohols and Amines to meso-Epoxides. -The first catalytic enantioselective addition of aliphatic alcohols (II) to meso-epoxides (I) is presented using a Sc(O-Tf)3-chiral bipyridine complex as catalyst. The reaction affords mono-protected anti-diols (III) in high yields and selectivities for aryl-substituted epoxides. The novel catalytic complex is successfully applied to the enantioselective addition of amines (IV) to meso-epoxides and gives N-protected amino alcohols (V) in comparably high yields and selectivities. -(SCHNEIDER*, C.; SREEKANTH, A. R.; MAI, E.; Angew.

Chiral recyclable dimeric and polymeric Cr(III) salen complexes catalyzed aminolytic kinetic resolution of trans‐aromatic epoxides under microwave irradiation

“…As the amount of nucleophile was reduced to 0.4 equiv, there was a slight improvement in the ee of the product but with significantly lower yield ( Table 1, entries 15 and 16). On increasing the amount of nucleophile (0.6-0.75 equiv) there was a steady decrease in the ee of product anti-b-aminoalcohol with concomitant increase in the ee of trans-stilbene oxide (83-96%; Table 1, entries [17][18][19][20]. Hence, the kinetic resolution reaction can be optimized depending upon which product (epoxide or aminoalcohol) is required in higher chiral purity by simply adjusting the amount of nucleophile (aniline) used.…”

“…trans-stilbene oxide does not commence ( Table 2, entries 11 and 12). AKR of trans-b-methyl styrene oxide with aniline gave exclusively anti-b-aminoalcohol with moderate ee and yield (Table 2, entries [13][14][15][16][17][18]. Based on the optical rotation studies for the products 7b-7c, their absolute configuration was shown to be 1S,2R.…”

Enantioselective desymmetrization of meso‐epoxides with anilines catalyzed by polymeric and monomeric Ti(IV) salen complexes

“…All products were characterized by appropriate spectroscopic techniques, microanalysis, LCMS, and optical rotation, which were found to be in consonance with the reported values. 7,8,19,20 Recycling of the Catalyst…”

“…In recent years, chiral amino alcohols have found a distinct role as chiral ligands for various metal-catalyzed asymmetric organic transformations. [1][2][3][4][5][6][7][8] To synthesize chiral b-amino alcohols, several strategies, namely, aminohydroxylation of olefins, 9,10 addition of a-hydroxy ketones to imines, [11][12][13] aminolytic kinetic resolution of racemic terminal/trans aromatic epoxides, [14][15][16][17][18] and asymmetric ring opening (ARO) of meso-epoxides, [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] have been reported in the literature. Among these, metal-catalyzed ARO of meso-epoxides with amines is one of the most elegant, atom efficient, and straightforward strategies for the synthesis of chiral b-amino alcohols.…”

“…Among these, metal-catalyzed ARO of meso-epoxides with amines is one of the most elegant, atom efficient, and straightforward strategies for the synthesis of chiral b-amino alcohols. Various chiral metal complexes of titanium, [19][20][21] vanadium, 22 niobium, 23,24 copper, 25 lanthanides, 4,6,8,26,27 chromium, 14,15 scandium, 7,28,29 indium, 30,31 and bismuth 32,33 have been used to catalyze this reaction effectively. Recently, Zhou et al 34 also reported the use of chiral Ti(IV) salen complex for ARO of meso epoxides with dithiophosphorous acid as nucleophile, but catalyst recycling was not attempted.…”